Feasibility and efficacy of adding high-intensity interval training to a multidisciplinary lifestyle intervention in children with obesity – a randomized controlled trial

Feasibility and efficacy of adding high-intensity interval training to a multidisciplinary lifestyle intervention in children with obesity – a randomized controlled trial | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Feasibility and efficacy of adding high-intensity interval training to a multidisciplinary lifestyle intervention in children with obesity – a randomized controlled trial Charlotte Eggertsen, Ryan Larsen, Kirsten Duch, Morten Simonsen, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4223158/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 10 Oct, 2024 Read the published version in International Journal of Obesity → Version 1 posted 10 You are reading this latest preprint version Abstract Background Multidisciplinary lifestyle interventions for children and adolescents with obesity often include recommendations regarding physical activity, but no structured exercise program. We hypothesized that adding high intensity interval training (HIIT) to a multidisciplinary lifestyle intervention would improve BMI z-score (primary outcome) and health-related quality of life (HRQOL). Methods This randomized controlled trial included 173 children and adolescents with obesity. Participants were allocated to a 12-months lifestyle intervention (N=83) or a 12-month lifestyle intervention accompanied by a 12-week HIIT program at intervention onset (N=90). The HIIT intervention consisted of three weekly sessions and included activities designed to elicit intensities >85% of maximal heart rate. Results Dropout rate was lower in HIIT compared to control at three months (7.8% vs. 20.5%) and 12 months (26.5% vs 48.2%). Changes in Body mass index (BMI) z-score did not differ between HIIT and control at 3 months (Mean Difference (MD): 0.01, 95% confidence interval (CI): -0.09; 0.12, P=0.82) or 12 months (MD: 0.06, CI: -0.07; 0.19, P=0.34). Across randomization (pooled data), BMI z-score was reduced by 0.11 (CI: 0.17; 0.06, P<0.01) at 3 months and 0.20 (CI: 0.26; 0.14, P<0.01) at 12 months. At 3 months, HIIT experienced a greater increase in HRQOL, with increases of 2.73 (CI: 0.01; 5.44, P=0.05) in PedsQL Child total score and 3.85 (CI: 0.96; 6.74, P<0.01) in psychosocial health score compared to control . At 12 months, PedsQL Child physical score was reduced by 6.89 (CI: 10.97; 2.83, P<0.01) in HIIT compared to control. Conclusion Adding a 12-week HIIT program did not further augment the effects of a 12-month lifestyle intervention on BMI z-score, but improved HRQOL after 3 months. Implementation of HIIT in a community-based setting was feasible and showed positive effects on adherence to the lifestyle intervention. Health sciences/Health care/Paediatrics Health sciences/Medical research/Clinical trial design/Randomized controlled trials Health sciences/Risk factors Figures Figure 1 Figure 2 Introduction Childhood obesity is a worldwide epidemic affecting both physical and mental health. In Denmark, up to 16% of children and adolescents suffer from overweight or obesity( 1 ). Children and adolescents with obesity are at increased risk of metabolic complications, such as pre-diabetes( 2 ), hypertension( 3 ), dyslipidaemia( 4 ), and excess fat deposition in the liver( 5 ). In addition, psychological problems, such as low quality of life and anxiety, are prevalent in this group of children and adolescents( 6 , 7 ). Childhood obesity often persists into adulthood, increasing the risk of cardiovascular diseases, type 2 diabetes, and various forms of cancer( 8 – 10 ). Most obesity-related complications may be reversible if weight status is reduced before puberty and early adulthood( 9 ), which underlines the need for effective treatment strategies targeting children and adolescents with obesity to mitigate the development of later morbidity and mortality. The Children’s Obesity Clinic´s Treatment (TCOCT) is a family-based multidisciplinary obesity treatment used in Denmark( 11 ). This approach comprises a lifestyle intervention addressing several aspects of everyday life, including recommendations on frequency and content of meals, physical activity, sleeping patterns, and psychosocial factors related to childhood obesity( 11 ). The TCOCT protocol improves BMI z-score, metabolic and cardiovascular parameters, and health-related quality of life (HRQOL) in both primary and tertiary care settings( 4 , 12 – 16 ). Notably, while physical activity is recommended, structured exercise is not an integrated element of the TCOCT protocol. Physical inactivity is an emerging problem among children and adolescents. In Denmark, only 26% of 11 to 15-year-old adolescents meet the recommended 60 minutes of moderate-to-vigorous physical activity daily( 17 ), and children and adolescents with obesity are often less active compared with their normal-weight peers( 18 ). Several studies have provided evidence indicating that high-intensity interval training (HIIT) reduces body weight and improves cardiovascular health and quality of life( 19 – 21 ). Therefore, this randomized controlled trial aimed to examine the efficacy and feasibility of adding a specialised community-based HIIT intervention to a multidisciplinary lifestyle intervention program (resembling the TCOCT) in children and adolescents with obesity. Our primary objective was to test the hypothesis that children and adolescents receiving HIIT in addition to TCOCT would experience greater reduction in BMI z-score compared to TCOCT. Secondary objectives were to examine changes in waist circumference, blood pressure, and HRQOL from baseline to 3 and 12-month follow-up between groups. Feasibility was assessed using rates of attendance (HIIT group) and dropout (both groups). Subjects and methods Study design and population: This study used a two-armed randomied controlled trial. At baseline, participants were randomized to 12 months of TCOCT (control group) or 12 months of TCOCT with 3 months supplementary HIIT (HIIT group) (Fig. 1 ). Randomization was conducted using a computerized randomization procedure using blocks of 4 to 6 participants, with individuals stratified on local municipality. Participants were recruited from 6 municipal obesity clinics in Northern Denmark and the outpatient clinic for childhood obesity treatment, Department of Paediatrics and Adolescent Medicine, Aalborg University Hospital. Inclusion criteria were: BMI > 90 percentile for age and sex by WHO growth charts 2006( 22 ), and age 9 to 16 years. Children and adolescents with severe physical or mental illness, which would complicate participation in the 12 weeks HIIT intervention, were not included. The trial followed the ethical guidelines of the Declaration of Helsinki and was approved by the Local Ethics Committee of North Denmark Region (ID: N-20200035). The project was reported according to CONSORT 2010 statement and was registered on ClinicalTrials.gov (ID: NCT05465057). Informed consent was signed by parents or legal guardians before participation. Lifestyle intervention: All enrolled children and adolescents were initially introduced to the TCOCT protocol( 11 ). Each participant was scheduled for follow-up visits in the outpatient or municipal obesity clinic by a trained paediatric nurse and dietician every 6 to 12 weeks. Based on information obtained from interview and physical examination, an individual treatment plan (consisting of 15 to 20 items) was outlined in collaboration with the family in accordance with the TCOCT protocol( 11 ). HIIT intervention: The HIIT protocol consisted of three weekly sessions of 45 to 50 minutes and was conducted in groups of 6 to 10 children and adolescents. The training sessions were conducted in the participant’s local environment and supervised by sports science or physiotherapy students. All HIIT activities were designed to elicit intensities > 85% of maximal heart rate in 4 bouts of 4-minute intervals, with 3 minutes of active recovery between bouts( 23 ). The activities were tailored to be playful, non-competitive, and comprised strength-based exercise, ball games, or running games. New activities were introduced regularly to maintain interest in the HIIT sessions. The intensity level was monitored and quantified using a real-time team heart rate (HR) system with Suunto dual comfort belts (Suunto, Vantaa, Finland) and iQniter cardio training software 3.5 (iQniter, Aalborg, Denmark). Activity intensity was defined as high (> 85%), moderate (60 to 85%), or low (< 60% of maximal HR). Each participant’s maximal HR was estimated using the revised age-predicted maximal heart rate Eq. (208–(0.7×age))( 24 ). Measurements Anthropometrics (height, weight, waist and hip circumference, BMI, BMI z-score), blood pressure, pubertal stage data, and HRQOL were measured at baseline, 3 month, and 12 months. Height was measured without shoes to the nearest 0.1 cm using a wall-mounted stadiometer, and weight was measured to the nearest 0.1 kg wearing light indoor clothes without shoes using a calibrated scale (Seca 799, Hamburg, Germany, or Tanita DC 360S, Soeborg, Denmark). BMI (kg/m 2 ) was converted into BMI z-scores according to the WHO Reference 2006( 22 ). Waist circumference was measured to the nearest 0.1 cm with participants standing using stretch-resistant tape at the midpoint level between the lowest rib and the top of the iliac crest. Blood pressure was measured on the right arm after 5 minutes of rest in a sitting position using an automated blood pressure monitor (Omron M7 Intelli IT, Kyoto, Japan). Blood pressure measurements were conducted three times, and the mean of the three recordings was reported. Evaluation of diastolic and systolic blood pressure percentiles was based on the individual sex, height, and age according to the AAP guidelines( 25 ). Psychological well-being and HRQOL were measured via validated questionnaires using the Pediatric Quality of Life Inventory, version 4.0 Generic Core Scales (PedsQL)( 26 ) and WHO-Five Well-Being Index (WHO-5)( 27 , 28 ). Statistics and data analysis: Sample size was calculated using a two-sided t-test for changes in the primary outcome measure, BMI z-score. Based on previous results( 14 , 29 ), a power of 80%, a significance level of 5%, a mean difference in BMI z-score of 0.2, and a standard deviation (SD) of 0.45, the total sample size was 162. Accounting for 25% dropout, the required sample size was 202 children and adolescents. Prior to analysis, all variables were checked for outliers and sample distribution. Baseline values are presented with mean and SD for continuous variables and count and percentage for categorical variables. A generalized linear mixed model (GLMM) with subjects as random intercept was used to estimate the mean difference (MD) between groups. Both a crude (adjusted for baseline scores) and an adjusted analysis were performed to estimate the effect of the HIIT intervention. The adjusted analysis included baseline score, puberty category, and sex. A GLMM was also used to examine overall changes over time. If difference between groups was observed, within-group changes were also reported. Missing values were handled by GLMM. Participants with a baseline measurement and at least one follow-up measurement were included in the analysis. For the HIIT group only, the attendance rate of ≥ 70% was accessed using a GLMM for both 3 and 12 months. Attendance rate was calculated as (number of sessions attended/total sessions offered)×100. All analyses are presented with 95% confidence intervals (CI) and a significance level of 5%. Analysis was done with STATA 18 (StataCorp LLC, TX, USA). Several sensitivity analyses were performed: i) missing values were treated as last value carried forward and as complete case analysis, ii) overall effect of sex was assessed for each visit and outcome measure using a GLMM, iii) a generalized linear model (GLM) was used to calculate the relative risk (RR) and odds ratio (OR) of dropout at 3 months based on baseline measures for each intervention group, iv) a yes/no variable indicating if participant’s training sessions were affected by the COVID-19 lockdown was added to the adjusted analysis, and the overall effect of the lockdown was assessed for each outcome measure. Results Recruitment and dropout: A total of 173 children and adolescents (101 boys, 12.3 ± 1.7 years) with a BMI z-score of 2.5 ± 0.6 participated in the study from October 2020 to May 2023. Baseline characteristics are presented in Table 1. A CONSORT diagram (Fig. 1 ) summarises the participant flow through each trial stage. During the 12-week intervention, the HIIT group experienced a dropout rate of 7.8% (CI: 2.3%; 13.3%), while the control group experienced a dropout rate of 20.5% (CI: 11.8%; 29.2%). Dropout in the HIIT group occurred particularly in the first two weeks of training (1 child and 3 adolescents) and after the COVID-19 lockdown (3 adolescents). At 12 months follow-up, the HIIT group experienced a 25.5% (CI: 16.5%; 34.5%) dropout, while to the control group experienced a dropout rate of 48.2% (CI: 37.5%; 58.9%). At 3 months, a one-unit higher BMI z-score resulted in a higher risk for dropout in the control group (RR: 2.20, CI: 0.96; 5.03, corresponding to an OR: 2.83, CI: 1.04; 7.71) and a lower risk for dropout in the HIIT group (RR: 0.39, CI: 0.12; 1.30, corresponding to an OR: 0.34, CI: 0.09; 1.30). Training intensity and attendance: A total of 90 children and adolescents participated in the HIIT intervention and showed an average attendance rate of 68.0 ± 23.2% over the 12-week intervention. Fifty-five (61.1%) children and adolescents completed ≥ 70% of the HIIT sessions. The average exercise session lasted 47.5 ± 10.5 minutes, and the participants spent on average 8.7 ± 4.8 minutes in high intensity, 31.5 ± 4.2 minutes in moderate intensity, and 6.7 ± 5.0 minutes in low intensity. BMI z-score and waist circumference We found no difference in BMI z-score between HIIT and control at 3 months (MD: 0.01, CI: -0.09; 0.12) or 12 months (MD: 0.06, CI: -0.07; 0.19). Similarly, no difference between groups were seen in waist circumference at 3 months (MD: 1.34 cm, CI: -1.58; 4.26) or 12 months (MD: 2.81 cm, CI: -0.51; 6.12) (Table 2). Adjustment and sensitivity analysis did not change the results (not shown). Across randomization (pooled data), BMI z-score was reduced by 0.11 (CI: 0.17; 0.06) at 3 months and by 0.20 (CI: 0.26; 0.14) at 12 months. There were no significant changes in waist circumference at 3 and 12 months (Table 3). Blood pressure No significant differences in diastolic or systolic blood pressure were found between groups (Table 2). Across randomization, there were no changes in diastolic blood pressure at 3 or 12 months (Table 3). However, systolic blood pressure was increased after 12 months (Table 3). At baseline, 4.6% of the children and adolescents had elevated systolic blood pressure (> 90th percentile) and 4.6% had hypertension (> 95th percentile). For diastolic blood pressure, 6.9% of the cohort had elevated diastolic blood pressure and 7.5% had hypertension at baseline. There were no significant changes in the distribution of these blood pressure categories at 3 or at 12 months. Quality of life: There were no differences between groups in WHO-5 well-being index after 3 or 12 months. The cohort showed an increase in WHO-5 score at 3 months, which did not sustain at 12 months (Table 3). At 3 months, the increase in HRQOL was greater in the HIIT group, with a mean difference in PedsQL child self-report, total score of 2.73 (CI: 0.01; 5.44), and a mean difference in psychosocial health score of 3.85 (CI: 0.96; 6.74) compared to the control group (Table 2). Within-group analysis showed an increase in PedsQL child self-report, total score of 5.55 (CI: 3.52; 7.58) in the HIIT group and 2.43 (CI: 0.25; 4.6) in the control group. The increase in psychosocial health score was 5.88 (CI: 3.72; 8.05) in the HIIT group and 1.42 (CI: -0.78; 3.62) in the control group. At 12 months, the control group experienced a greater increase in PedsQL child self-report physical score than the HIIT group (Table 2). The increase in physical score was 9.14 (CI: 5.51; 12.77) in the control group and 1.86 (CI: -1.14; 4.87) in the HIIT group. The PedsQL parents proxy report showed higher scores, yet not significant, in all three domains in the HIIT group at 3 months (Table 2). At 12 months, physical scores were greater in the control group compared with the HIIT group (Table 2). Sensitivity analysis: Sensitivity analysis showed a larger mean reduction in BMI z-score in boys compared to girls at 12 months of 0.16 (CI: 0.29; 0.03), corrected for baseline BMI z-score. A greater reduction in diastolic blood pressure was seen in boys compared to girls at 12 months (MD: 3.58, CI: 5.77; 1.39). No differences between sexes were found for waist circumference or systolic blood pressure. For HRQOL, the WHO-5 index for boys increased more than for girls at 12 months (MD: 7.89; CI: 1.95; 13.84). The PedsQL total (MD: 2.81; CI: 0.08; 5.53) and psychosocial domains (MD: 3.14; CI: 0.23; 6.04) increased for boys compared to girls at 3 months. These differences between sexes were also evident at 12 months in PedsQL total (MD: 4.21; CI: 0.99; 7.44), psychosocial (MD: 4.25; CI: 0.85; 7.64), and physical domains (MD: 4.87; CI: 0.73; 9.01). Participants who attended ≥ 70% of the training sessions exhibited greater PedsQL total score and physical score at 3 months than those who attended < 70%. There were no other differences between these two sub-groups (Suppl.: Table 4). Sensitivity analyses for missing observations did not change the results. Adjusting for COVID-19 lockdown did not affect the group differences and changes over time (data not shown). However, at 3 months, waist circumference was significantly increased among participants whose intervention was affected by COVID-19 compared to those unaffected (MD: 4.1, CI: 1.07; 7.15). Discussion This two-armed randomized controlled trial aimed to examine the feasibility and efficacy of adding a 12-week HIIT program to a 12-month family-based multidisciplinary intervention. We found no differences in the primary outcome, BMI z-score, between the HIIT and control group. However, across randomization, significant reductions in BMI z-score were found at 3 months and 12 months follow-up. In addition, at 3 months HRQOL was improved in the HIIT group. Sensitivity analyses indicated that participation in HIIT resulted in lower dropout and better adherence to the lifestyle intervention. Effects of TCOCT and exercise on BMI z-score Across randomization, we found significant reductions in BMI z-score of 0.11 points at 3 months and 0.20 points after 12 months. In addition, boys experienced a greater reduction in BMI z-score than girls at 12 months. Consistent with these results, a cohort of Danish children admitted to a tertiary obesity clinic, showed reductions in BMI z-score of 0.30 (CI: 0.39; 0.21) in boys and 0.19 (CI: 0.25; 0.13) in girls after one year of TCOCT intervention( 12 ). Our results thus reinforce that multidisciplinary family-based lifestyle intervention (i.e., TCOCT) is effective in improving BMI z-score in children and adolescents with obesity, with possible greater benefit for boys. BMI z-score reductions of more than 0.25 points have been associated with improvements in cardiometabolic risk factors( 30 ), but even a reduction in BMI z-score of 0.10 has been associated with health benefits among children with obesity( 29 ). A novel aspect of our study was to examine if adding a 3-month HIIT protocol to the TCOCT intervention would augment a reduction in BMI z-score at 3 or 12 months follow-up. We found no differences between groups. It is possible that the short duration of the HIIT intervention provided insufficient stimulus for eliciting changes in body composition. However, the lack of additive effects of HIIT is consistent with previous studies reporting only modest effects of exercise interventions on BMI z-score and waist circumference among children and adolescents with obesity( 21 ). A recent study (EFRIGO) that included a 6-month supplementary HIIT intervention to a multidisciplinary lifestyle intervention showed no difference in BMI between groups. The EFIGRO study used a longer exercise intervention (22 weeks) and a larger weekly training volume (3 sessions of 90 minutes) than the present study( 31 ). Taken together, these results suggest that adding exercise to multidisciplinary lifestyle interventions do not always promote greater changes in BMI z-score in children and adolescents with obesity( 21 ). Notably, the EFIGRO study reported a greater reduction in hepatic fat and LDL cholesterol in the HIIT group compared with the control group (lifestyle intervention only)( 31 ). Consistent with these findings, a Danish study reported metabolic improvements in 80% of the children participating in a lifestyle intervention despite no change in BMI z-score( 32 ). These results suggest that multidisciplinary lifestyle intervention, including recommendations about physical activity or an exercise program, may elicit metabolic improvements, even without marked reductions in BMI z-score. Effects of TCOCT and HIIT on blood pressure We found no clinically relevant changes in blood pressure. At baseline, the majority of the participants had blood pressure within the normal range, which limits the potential for improvements in response to the interventions. Less than 8% of the participants showed signs of hypertension, which is lower than the prevalence of 16% reported by Hvidt et al. in a comparable cohort of Danish children and adolescents with obesity( 3 ). Effects of lifestyle interventions and HIIT on HRQOL The physiological links between obesity-related risk behaviors, including physical inactivity and psychosocial health, are well-known and assumed to be bi-directional( 33 ). Studies have shown an inverse relationship between obesity and well-being on both physical and psychosocial parameters( 6 ). A novel result from the present study was that adding a 3-month HIIT program to the TCOCT protocol resulted in a greater improvement in HRQOL after 3 months, measured by PedsQL. Specifically, the HIIT group reported a greater increase in PedsQL child total score and psychosocial health score. Furthermore, the boys experienced overall greater improvement in HRQOL than the girls. These findings extend results from previous studies investigating the effects of exercise interventions on HRQOL( 34 ). Goldfield et al. reported an increase in PedsQL child total score of 5.5 (CI: 1.4; 9.6) after a 22-week combined lifestyle and aerobic exercise intervention with 4 weekly training sessions compared to control groups( 35 ). Together, these results emphasize the relevance of including physical activity programs as a central element in obesity treatment interventions. Consistent with Goldfield et al., our sensitivity analysis showed that participants with ≥ 70% attendance in HIIT sessions exhibited a greater increase in HRQOL, particularly in the physical score. This is an important finding because enjoyment and positive feelings of competence and confidence are the main psychological drivers of engagement and adherence to physical activities( 36 , 37 ). In turn, this may help to improve mental health factors in this group of vulnerable children and adolescents( 38 ). At 12 months, we found lower levels of HRQOL in the HIIT group compared to the control group. A possible explanation is that termination of the 3-month HIIT program left many of the HIIT participants with a feeling of sadness and abandonment. This interpretation is supported by feedback from the HIIT participants and their families, who noted that they could not find a suitable exercise program to replace the HIIT. This emphasizes the importance of focusing on implementing permanent exercise programs tailored for this population. HIIT intervention The attendance rate for HIIT sessions reached 68% across the 3 months, which is high compared to reports from similar studies( 39 , 40 ). In a 6-months HIIT intervention in adolescents with overweight, Herget et al. reported that the attendance rate declined from 75% in the first two months to 15% in the last three months( 40 ). The dropout rate of 7.8% in our HIIT group during the first three months was lower than the dropout rate in the control group (20.5%). Notably, the dropout rate at 12 months was also lower in the HIIT group (25.5%) compared to the control group (48.2%). Jørgensen et al reported a dropout rate of 43% after 12 month TCOCT protocol in a similar cohort of Danish children with obesity( 13 ). Taken together, these observations indicate that participation in a tailored exercise program increases adherence to lifestyle interventions for treating obesity. In addition, our analyses revealed that a one-unit higher BMI z-score in the control group resulted in a higher RR for dropout after 3 months, which was not seen in the HIIT group. This result supports that exercise programs may be a viable option in reducing attrition in programs focused on treating obesity, particularly for children and adolescents with very high BMI z-scores. Childhood is a vulnerable period of life, where psychosocial aspects are important for well-being. Adolescence is known to be the life stage with the biggest dropout in sports and physical activity programs( 36 , 41 ). Psychological issues and concerns about appearance have been found to predict low adherence to training interventions in adolescents with obesity( 39 ). Enjoyment, family support, creating social relations, and full participation in age-appropriate activities are important elements for children and adolescents in order to overcome challenges in relation to physical activities( 42 ). The fact that our HIIT intervention was created with a playful, supportive, and non-competitive perspective through various modalities may have positively influenced adherence and dropout rates. These results support the importance of establishing tailored training interventions that embrace a safe and non-stigmatizing environment with enjoyable and motivating activities to ensure long-term adherence for children and adolescents. In addition, taking advantage of continouos HR monitoring allowed us to demonstrate that the HIIT sessions were effective in eliciting 40 minutes of moderate-to-high intensity physical activity (> 60% maximal HR) which constitutes a large proportion of recommended daily physical activity. Strengths and limitations A limitation of the study is that we only enrolled and randomized 173 participants, which is fewer than the estimated number from the sample size calculation (N = 202). Our study was conducted from 2020–2023, and the intervention (including recruitment) was challenged by the COVID-19 pandemic and lockdown periods in the winter of 2020/2021. We experienced a general reluctance to participate in the intervention after the COVID-19 lockdown, which hindered recruitment for the study. The sensitivity analysis showed that COVID-19 did not affect the difference across intervention, but might have decreased the signal from the intervention. Notable, participants affected by COVID-19 experienced a significant increase in waist circumference at 3 months. This could have been mediated by lower levels of habitual physical activity and increased sedentary behavior during the lockdown periods, as reported in other studies( 43 , 44 ). A strength of our study is the randomized design, which minimized the risk of selection bias. In addition, we were able to adjust the HIIT modalities according to the childrens preferences and competences, which allowed children and adolescents with minor physical and psychological disabilities to participate. This approach embraced the great heterogeneity in the population of children and adolescents with obesity. In conclusion, our results show that it is feasible to implement 3 months of HIIT in a community-based setting tailored for children and adolescents with obesity. In fact, participation in the HIIT program appeared to promote greater adherence to the lifestyle intervention, particularly for those with severe obesity. Addition of supervised HIIT training to the TCOCT protocol did not augment the reduction in BMI z-score. However, HIIT was accompanied by greater HRQOL at 3 months, compared with the control group. Overall, the boys experienced greater effects of the intervention on BMI z-score and HRQOL. Future studies should further investigate the potential of using tailored exercise programs in community-based settings to promote greater adherence to lifestyle interventions in children and adolescents with obesity. Declarations Acknowledgements: The project was supported by Steno Diabetes Center North Denmark, Trygfonden (Grant No. 149852), Danish Regions (Grant No. R201-A4487), A.P. Moller Foundation (Grant No. 17-L-0393), Beckett Foundation (Grant No. 17-2-1655), Svend Andersens Foundation and Memorial legatee for Carpenter Jørgen Holm and wife Elisa F. Hansen (Grant No. 20094) We thank iQniter (Aalborg, Denmark) for lending us the heart rate system. iQniter had no influence on the interpretation of the results. Authors contributions: CNE was responsible for designing the protocol, organising the project and HIIT intervention, collaborate with municipal co-workers and HIIT trainers, conducting clinical examinations, analysing the data and drafting the manuscript. RGL and SH contributed as main supervisors in the design of the protocol, analysis of data, interpretation of results, and writing of the manuscript. ETV contributed to designing and writing the project protocol, interpreting the results and writing the manuscript. KD contributed to the statistical analyses and interpretation as well as writing the manuscript. MBS contributed to the HIIT intervention, including design, heart rate monitoring, maintenance of equipment, data extraction and analysis, and provided feedback on the manuscript. CBC contributed with conducting clinical examinations, data extraction and analyses (blood pressure data) as well as writing the manuscript. TCW contributed to the design of the protocol, recruiting participants for the study, conducting clinical examinations, interpreting the results and provided feedback on the manuscript. JBF contributed to the design of the protocol, conducting clinical examinations, interpreting the results and provided feedback on the manuscript. AH contributed to the design of the protocol, supervision and support during the trial, organising parts of the clinical examinations, interpreting the results and provided feedback on the manuscript. TS contributed to the design of the protocol, supported and organised collaboration with co-workers and leaders in the municipalities and provided feedback on the manuscript. Competing interests: The authors declare no competing financial interests. Data availability statement: Data is available upon reasonable request. References Madsen KR, Román JEI, Damsgaard MT, Holstein BE, Kristoffersen MJ PT et al. Skolebørnsundersøgelsen 2022 [Internet]. København; 2023. Available from: https://www.hbsc.dk/ Hagman E, Reinehr T, Kowalski J, Ekbom A, Marcus C, Holl RW. Impaired fasting glucose prevalence in two nationwide cohorts of obese children and adolescents. Int J Obes (Lond). 2014;38(1):40–5. Hvidt KN, Olsen MH, Ibsen H, Holm J-C. 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Rasmussen M, Kierkegaard L, Rosenwein SV, Holstein BE, Damsgaard MT DP. Skolebørnsundersøgelsen 2018: Helbred, trivsel og sundhedsadfærd blandt 11-, 13- og 15-årige skoleelever i Danmark. [Internet]. København; 2019. Available from: https://www.hbsc.dk/ McManus AM, Mellecker RR. Physical activity and obese children. J Sport Heal Sci. 2012;1(3):141–8. Martland R, Mondelli V, Gaughran F, Stubbs B. Can high-intensity interval training improve physical and mental health outcomes? A meta-review of 33 systematic reviews across the lifespan. J Sports Sci. 2020;38(4):430–69. Cao M, Quan M, Zhuang J. Effect of high-intensity interval training versus moderate-intensity continuous training on cardiorespiratory fitness in children and adolescents: A meta-analysis. Int J Environ Res Public Health. 2019;16(9):1533. García-Hermoso A, Ramírez-Vélez R, Saavedra JM. Exercise, health outcomes, and pædiatric obesity: A systematic review of meta-analyses. Vol. 22, Journal of Science and Medicine in Sport. Elsevier Ltd; 2019. p. 76–84. WHO Multicentre Growth Reference Study Group (2006). WHO Child Growth Standards: Length/height-for-age, weight-for-age, weight-for-length, weight-for-height and body mass index-for-age: Methods and development. Geneva World Heal Organ [Internet].:312. Available from: https://www.who.int/tools/growth-reference-data-for-5to19-years/indicators/bmi-for-age Tjønna AE, Stølen TO, Bye A, Volden M, Slørdahl SA, Ødegård R, et al. Aerobic interval training reduces cardiovascular risk factors more than a multitreatment approach in overweight adolescents. Clin Sci. 2009;116(4):317–26. Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol. 2001;37(1):153–6. National High Blood Pressure Education Program Wor H. The fourth report on the diagnosis, evaluation, and treatment of high blood pressure in children and adolescents. Pediatrics. 2004;114(2):555–76. Varni JW, Seid M, Kurtin PS. PedsQL 4.0: reliability and validity of the Pediatric Quality of Life Inventory version 4.0 generic core scales in healthy and patient populations. Med Care. 2001;39(8):800–12. Allgaier A-K, Pietsch K, Frühe B, Prast E, Sigl-Glöckner J, Schulte-Körne G, et al. Depression in pediatric care: is the WHO-Five Well-Being Index a valid screening instrument for children and adolescents? Gen Hosp Psychiatry. 2012;34(3):234–41. Topp CW, Østergaard SD, Søndergaard S, Bech P. The WHO-5 well-being index: A systematic review of the literature. Psychother Psychosom. 2015;84(3):167–76. Croker H, Viner RM, Nicholls D, Haroun D, Chadwick P, Edwards C, et al. Family-based behavioural treatment of childhood obesity in a UK national health service setting: randomized controlled trial. Int J Obes. 2012;36(1):16–26. Reinehr T, Lass N, Toschke C, Rothermel J, Lanzinger S, Holl RW. Which amount of BMI-SDS reduction is necessary to improve cardiovascular risk factors in overweight children? J Clin Endocrinol Metab. 2016;101(8):3171–9. Labayen I, Medrano M, Arenaza L, Máz E, Osés M, Martínez-Vizcáno V, et al. Effects of exercise in addition to a family-based lifestyle intervention program on hepatic fat in children with overweight. Diabetes Care. 2020;43(2):306–13. Nielsen TRH, Fonvig CE, Dahl M, Mollerup PM, Lausten-Thomsen U, Pedersen O, et al. Childhood obesity treatment; Effects on BMI SDS, body composition, and fasting plasma lipid concentrations. PLoS One. 2018;13(2):1–18. Mansur RB, Brietzke E, McIntyre RS. Is there a “metabolic-mood syndrome”? A review of the relationship between obesity and mood disorders. Neurosci Biobehav Rev. 2015;52:89–104. Rastogi S, Cadmus-Bertram L, Meyers L. Psychosocial Effects of Physical Activity Interventions for Preschoolers, Children, and Adolescents: Role of Intervention Settings. Am J Heal Promot. 2023;37(4):538–54. Goldfield GS, Kenny GP, Alberga AS, Tulloch HE, Doucette S, Cameron JD, et al. Effects of aerobic or resistance training or both on health-related quality of life in youth with obesity: the HEARTY Trial. Appl Physiol Nutr Metab. 2017;42(4):361–70. Stankov I, Olds T, Cargo M. Overweight and obese adolescents: What turns them off physical activity? Int J Behav Nutr Phys Act. 2012;9(1):53–53. Paponetti MK, Zwolski C, Porter R, Paterno M V. Leveraging the construct of physical literacy to promote physical activity for youth with obesity – A qualitative analysis of physical therapists’ perceptions. Obes Pillars. 2023;5:100054. Daley AJ, Copeland RJ, Wright NP, Roalfe A, Wales JKH. Exercise Therapy as a Treatment for Psychopathologic Conditions in Obese and Morbidly Obese Adolescents: A Randomized, Controlled Trial. Pediatr. 2006;118(5):2126–34. Alberga AS, Sigal RJ, Sweet SN, Doucette S, Russell-Mayhew S, Tulloch H, et al. Understanding low adherence to an exercise program for adolescents with obesity: the HEARTY trial. Obes Sci Pract. 2019;5(5):437–48. Herget S, Reichardt S, Grimm A, Petroff D, Käpplinger J, Haase M, et al. High-intensity interval training for overweight adolescents: Program acceptance of a media supported intervention and changes in body composition. Int J Environ Res Public Health. 2016;13(11). Guthold R, Stevens GA, Riley LM, Bull FC. Global trends in insufficient physical activity among adolescents: a pooled analysis of 298 population-based surveys with 1·6 million participants. Lancet Child Adolesc Heal. 2020;4(1):23–35. Foster C, Moore JB, Singletary CR, Skelton JA. Physical activity and family-based obesity treatment: a review of expert recommendations on physical activity in youth. Vol. 8, Clinical obesity. 2018. p. 68–79. Schmidt SCE, Anedda B, Burchartz A, Eichsteller A, Kolb S, Nigg C, et al. Physical activity and screen time of children and adolescents before and during the COVID-19 lockdown in Germany: a natural experiment. Sci Rep. 2020;10(1):1–12. Velde G, Lubrecht J, Arayess L, Loo C, Hesselink M, Reijnders D, et al. Physical activity behaviour and screen time in Dutch children during the COVID-19 pandemic: Pre‐, during‐ and post‐school closures. Pediatr Obes. 2021;16(9):e12779 -n/a . Tables Table 1 to 3 are available in the Supplementary Files section. Additional Declarations There is NO conflict of interest to disclose Supplementary Files Table1.xlsx Table2.xlsx Table3.xlsx Supplementarytable45.pdf Cite Share Download PDF Status: Published Journal Publication published 10 Oct, 2024 Read the published version in International Journal of Obesity → Version 1 posted Editorial decision: revise 25 Jul, 2024 Review # 3 received at journal 17 Jul, 2024 Reviewer # 3 agreed at journal 21 Jun, 2024 Review # 2 received at journal 21 May, 2024 Reviewer # 2 agreed at journal 25 Apr, 2024 Reviewer # 1 agreed at journal 22 Apr, 2024 Reviewers invited by journal 13 Apr, 2024 Submission checks completed at journal 08 Apr, 2024 Editor assigned by journal 05 Apr, 2024 First submitted to journal 05 Apr, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4223158","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":290747466,"identity":"a3a11634-1698-4b71-adf8-180e5a831eff","order_by":0,"name":"Charlotte 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13:00:35","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4223158/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4223158/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41366-024-01645-w","type":"published","date":"2024-10-10T04:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":55006996,"identity":"1c133b61-b82b-44e6-a274-6b0ba9c00c27","added_by":"auto","created_at":"2024-04-19 18:59:28","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":40033,"visible":true,"origin":"","legend":"\u003cp\u003eFlowchart showing participation through the trial.\u003c/p\u003e","description":"","filename":"Figure112.png","url":"https://assets-eu.researchsquare.com/files/rs-4223158/v1/097680db831f55f41c123c6e.png"},{"id":55006999,"identity":"d082767e-0a90-43c6-8e37-71362ff2b48f","added_by":"auto","created_at":"2024-04-19 18:59:29","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":53817,"visible":true,"origin":"","legend":"\u003cp\u003eMean difference between groups from baseline to 3 and 12-month follow-up, using baseline values as references. Shaded area represents 95% confidence intervals.\u003c/p\u003e\n\u003cp\u003eAbbreviations: BMI: Body Mass Index, WHO-5: WHO-Five Well-Being Index, PedsQL: Pediatric Quality of Life Inventory, version 4.0 Generic Core Scales\u003c/p\u003e","description":"","filename":"Figure29.png","url":"https://assets-eu.researchsquare.com/files/rs-4223158/v1/76878186aec4a585f087d95f.png"},{"id":66639463,"identity":"7cbb7371-0546-4d6f-a4c2-211f4312f0fe","added_by":"auto","created_at":"2024-10-15 06:00:03","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":753430,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4223158/v1/e3851ac3-f129-42e7-8784-8c262d982311.pdf"},{"id":55007002,"identity":"3d0bbf4e-d768-4b7c-9069-feb012487771","added_by":"auto","created_at":"2024-04-19 18:59:29","extension":"xlsx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":11855,"visible":true,"origin":"","legend":"","description":"","filename":"Table1.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-4223158/v1/b0ba44e9c0386e02a88c1917.xlsx"},{"id":55008663,"identity":"1caac43f-9ea3-4f48-b041-9ad4b68740dd","added_by":"auto","created_at":"2024-04-19 19:07:29","extension":"xlsx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":10956,"visible":true,"origin":"","legend":"","description":"","filename":"Table2.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-4223158/v1/cc973141a0a8c5933672b149.xlsx"},{"id":55007003,"identity":"873addeb-3600-4989-b43b-53de23da0de2","added_by":"auto","created_at":"2024-04-19 18:59:29","extension":"xlsx","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":11565,"visible":true,"origin":"","legend":"","description":"","filename":"Table3.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-4223158/v1/9297a577a3265bb1615e6ca8.xlsx"},{"id":55007001,"identity":"bc4d0f69-a212-4b58-ae18-202444d18dc6","added_by":"auto","created_at":"2024-04-19 18:59:29","extension":"pdf","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":192701,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"Supplementarytable45.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4223158/v1/c8525225b2093c8df4dd83fd.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e conflict of interest to disclose","formattedTitle":"Feasibility and efficacy of adding high-intensity interval training to a multidisciplinary lifestyle intervention in children with obesity – a randomized controlled trial","fulltext":[{"header":"Introduction","content":"\u003cp\u003eChildhood obesity is a worldwide epidemic affecting both physical and mental health.\u003c/p\u003e \u003cp\u003eIn Denmark, up to 16% of children and adolescents suffer from overweight or obesity(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). Children and adolescents with obesity are at increased risk of metabolic complications, such as pre-diabetes(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e), hypertension(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e), dyslipidaemia(\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e), and excess fat deposition in the liver(\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). In addition, psychological problems, such as low quality of life and anxiety, are prevalent in this group of children and adolescents(\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). Childhood obesity often persists into adulthood, increasing the risk of cardiovascular diseases, type 2 diabetes, and various forms of cancer(\u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). Most obesity-related complications may be reversible if weight status is reduced before puberty and early adulthood(\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e), which underlines the need for effective treatment strategies targeting children and adolescents with obesity to mitigate the development of later morbidity and mortality.\u003c/p\u003e \u003cp\u003eThe Children\u0026rsquo;s Obesity Clinic\u0026acute;s Treatment (TCOCT) is a family-based multidisciplinary obesity treatment used in Denmark(\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). This approach comprises a lifestyle intervention addressing several aspects of everyday life, including recommendations on frequency and content of meals, physical activity, sleeping patterns, and psychosocial factors related to childhood obesity(\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). The TCOCT protocol improves BMI z-score, metabolic and cardiovascular parameters, and health-related quality of life (HRQOL) in both primary and tertiary care settings(\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan additionalcitationids=\"CR13 CR14 CR15\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). Notably, while physical activity is recommended, structured exercise is not an integrated element of the TCOCT protocol.\u003c/p\u003e \u003cp\u003ePhysical inactivity is an emerging problem among children and adolescents. In Denmark, only 26% of 11 to 15-year-old adolescents meet the recommended 60 minutes of moderate-to-vigorous physical activity daily(\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e), and children and adolescents with obesity are often less active compared with their normal-weight peers(\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eSeveral studies have provided evidence indicating that high-intensity interval training (HIIT) reduces body weight and improves cardiovascular health and quality of life(\u003cspan additionalcitationids=\"CR20\" citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTherefore, this randomized controlled trial aimed to examine the efficacy and feasibility of adding a specialised community-based HIIT intervention to a multidisciplinary lifestyle intervention program (resembling the TCOCT) in children and adolescents with obesity. Our primary objective was to test the hypothesis that children and adolescents receiving HIIT in addition to TCOCT would experience greater reduction in BMI z-score compared to TCOCT. Secondary objectives were to examine changes in waist circumference, blood pressure, and HRQOL from baseline to 3 and 12-month follow-up between groups. Feasibility was assessed using rates of attendance (HIIT group) and dropout (both groups).\u003c/p\u003e"},{"header":"Subjects and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy design and population:\u003c/h2\u003e \u003cp\u003eThis study used a two-armed randomied controlled trial. At baseline, participants were randomized to 12 months of TCOCT (control group) or 12 months of TCOCT with 3 months supplementary HIIT (HIIT group) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eRandomization was conducted using a computerized randomization procedure using blocks of 4 to 6 participants, with individuals stratified on local municipality.\u003c/p\u003e \u003cp\u003e Participants were recruited from 6 municipal obesity clinics in Northern Denmark and the outpatient clinic for childhood obesity treatment, Department of Paediatrics and Adolescent Medicine, Aalborg University Hospital. Inclusion criteria were: BMI\u0026thinsp;\u0026gt;\u0026thinsp;90 percentile for age and sex by WHO growth charts 2006(\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e), and age 9 to 16 years.\u003c/p\u003e \u003cp\u003eChildren and adolescents with severe physical or mental illness, which would complicate participation in the 12 weeks HIIT intervention, were not included.\u003c/p\u003e \u003cp\u003e The trial followed the ethical guidelines of the Declaration of Helsinki and was approved by the Local Ethics Committee of North Denmark Region (ID: N-20200035). The project was reported according to CONSORT 2010 statement and was registered on ClinicalTrials.gov (ID: NCT05465057). Informed consent was signed by parents or legal guardians before participation.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eLifestyle intervention:\u003c/h2\u003e \u003cp\u003eAll enrolled children and adolescents were initially introduced to the TCOCT protocol(\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). Each participant was scheduled for follow-up visits in the outpatient or municipal obesity clinic by a trained paediatric nurse and dietician every 6 to 12 weeks. Based on information obtained from interview and physical examination, an individual treatment plan (consisting of 15 to 20 items) was outlined in collaboration with the family in accordance with the TCOCT protocol(\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eHIIT intervention:\u003c/h2\u003e \u003cp\u003eThe HIIT protocol consisted of three weekly sessions of 45 to 50 minutes and was conducted in groups of 6 to 10 children and adolescents. The training sessions were conducted in the participant\u0026rsquo;s local environment and supervised by sports science or physiotherapy students. All HIIT activities were designed to elicit intensities\u0026thinsp;\u0026gt;\u0026thinsp;85% of maximal heart rate in 4 bouts of 4-minute intervals, with 3 minutes of active recovery between bouts(\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e). The activities were tailored to be playful, non-competitive, and comprised strength-based exercise, ball games, or running games. New activities were introduced regularly to maintain interest in the HIIT sessions. The intensity level was monitored and quantified using a real-time team heart rate (HR) system with Suunto dual comfort belts (Suunto, Vantaa, Finland) and iQniter cardio training software 3.5 (iQniter, Aalborg, Denmark). Activity intensity was defined as high (\u0026gt;\u0026thinsp;85%), moderate (60 to 85%), or low (\u0026lt;\u0026thinsp;60% of maximal HR). Each participant\u0026rsquo;s maximal HR was estimated using the revised age-predicted maximal heart rate Eq.\u0026nbsp;(208\u0026ndash;(0.7\u0026times;age))(\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eMeasurements\u003c/h2\u003e \u003cp\u003eAnthropometrics (height, weight, waist and hip circumference, BMI, BMI z-score), blood pressure, pubertal stage data, and HRQOL were measured at baseline, 3 month, and 12 months.\u003c/p\u003e \u003cp\u003eHeight was measured without shoes to the nearest 0.1 cm using a wall-mounted stadiometer, and weight was measured to the nearest 0.1 kg wearing light indoor clothes without shoes using a calibrated scale (Seca 799, Hamburg, Germany, or Tanita DC 360S, Soeborg, Denmark). BMI (kg/m\u003csup\u003e2\u003c/sup\u003e) was converted into BMI z-scores according to the WHO Reference 2006(\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e). Waist circumference was measured to the nearest 0.1 cm with participants standing using stretch-resistant tape at the midpoint level between the lowest rib and the top of the iliac crest. Blood pressure was measured on the right arm after 5 minutes of rest in a sitting position using an automated blood pressure monitor (Omron M7 Intelli IT, Kyoto, Japan). Blood pressure measurements were conducted three times, and the mean of the three recordings was reported. Evaluation of diastolic and systolic blood pressure percentiles was based on the individual sex, height, and age according to the AAP guidelines(\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e).\u003c/p\u003e \u003cp\u003ePsychological well-being and HRQOL were measured via validated questionnaires using the Pediatric Quality of Life Inventory, version 4.0 Generic Core Scales (PedsQL)(\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e) and WHO-Five Well-Being Index (WHO-5)(\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eStatistics and data analysis:\u003c/h2\u003e \u003cp\u003eSample size was calculated using a two-sided t-test for changes in the primary outcome measure, BMI z-score. Based on previous results(\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e), a power of 80%, a significance level of 5%, a mean difference in BMI z-score of 0.2, and a standard deviation (SD) of 0.45, the total sample size was 162. Accounting for 25% dropout, the required sample size was 202 children and adolescents.\u003c/p\u003e \u003cp\u003ePrior to analysis, all variables were checked for outliers and sample distribution. Baseline values are presented with mean and SD for continuous variables and count and percentage for categorical variables.\u003c/p\u003e \u003cp\u003eA generalized linear mixed model (GLMM) with subjects as random intercept was used to estimate the mean difference (MD) between groups. Both a crude (adjusted for baseline scores) and an adjusted analysis were performed to estimate the effect of the HIIT intervention. The adjusted analysis included baseline score, puberty category, and sex. A GLMM was also used to examine overall changes over time. If difference between groups was observed, within-group changes were also reported. Missing values were handled by GLMM.\u003c/p\u003e \u003cp\u003eParticipants with a baseline measurement and at least one follow-up measurement were included in the analysis.\u003c/p\u003e \u003cp\u003eFor the HIIT group only, the attendance rate of \u0026ge;\u0026thinsp;70% was accessed using a GLMM for both 3 and 12 months. Attendance rate was calculated as (number of sessions attended/total sessions offered)\u0026times;100.\u003c/p\u003e \u003cp\u003eAll analyses are presented with 95% confidence intervals (CI) and a significance level of 5%. Analysis was done with STATA 18 (StataCorp LLC, TX, USA).\u003c/p\u003e \u003cp\u003eSeveral sensitivity analyses were performed: i) missing values were treated as last value carried forward and as complete case analysis, ii) overall effect of sex was assessed for each visit and outcome measure using a GLMM, iii) a generalized linear model (GLM) was used to calculate the relative risk (RR) and odds ratio (OR) of dropout at 3 months based on baseline measures for each intervention group, iv) a yes/no variable indicating if participant\u0026rsquo;s training sessions were affected by the COVID-19 lockdown was added to the adjusted analysis, and the overall effect of the lockdown was assessed for each outcome measure.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eRecruitment and dropout:\u003c/h2\u003e \u003cp\u003eA total of 173 children and adolescents (101 boys, 12.3\u0026thinsp;\u0026plusmn;\u0026thinsp;1.7 years) with a BMI z-score of 2.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.6 participated in the study from October 2020 to May 2023. Baseline characteristics are presented in Table\u0026nbsp;1. A CONSORT diagram (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) summarises the participant flow through each trial stage.\u003c/p\u003e \u003cp\u003eDuring the 12-week intervention, the HIIT group experienced a dropout rate of 7.8% (CI: 2.3%; 13.3%), while the control group experienced a dropout rate of 20.5% (CI: 11.8%; 29.2%). Dropout in the HIIT group occurred particularly in the first two weeks of training (1 child and 3 adolescents) and after the COVID-19 lockdown (3 adolescents). At 12 months follow-up, the HIIT group experienced a 25.5% (CI: 16.5%; 34.5%) dropout, while to the control group experienced a dropout rate of 48.2% (CI: 37.5%; 58.9%).\u003c/p\u003e \u003cp\u003eAt 3 months, a one-unit higher BMI z-score resulted in a higher risk for dropout in the control group (RR: 2.20, CI: 0.96; 5.03, corresponding to an OR: 2.83, CI: 1.04; 7.71) and a lower risk for dropout in the HIIT group (RR: 0.39, CI: 0.12; 1.30, corresponding to an OR: 0.34, CI: 0.09; 1.30).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eTraining intensity and attendance:\u003c/h2\u003e \u003cp\u003eA total of 90 children and adolescents participated in the HIIT intervention and showed an average attendance rate of 68.0\u0026thinsp;\u0026plusmn;\u0026thinsp;23.2% over the 12-week intervention. Fifty-five (61.1%) children and adolescents completed\u0026thinsp;\u0026ge;\u0026thinsp;70% of the HIIT sessions.\u003c/p\u003e \u003cp\u003e The average exercise session lasted 47.5\u0026thinsp;\u0026plusmn;\u0026thinsp;10.5 minutes, and the participants spent on average 8.7\u0026thinsp;\u0026plusmn;\u0026thinsp;4.8 minutes in high intensity, 31.5\u0026thinsp;\u0026plusmn;\u0026thinsp;4.2 minutes in moderate intensity, and 6.7\u0026thinsp;\u0026plusmn;\u0026thinsp;5.0 minutes in low intensity.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eBMI z-score and waist circumference\u003c/h2\u003e \u003cp\u003eWe found no difference in BMI z-score between HIIT and control at 3 months (MD: 0.01, CI: -0.09; 0.12) or 12 months (MD: 0.06, CI: -0.07; 0.19). Similarly, no difference between groups were seen in waist circumference at 3 months (MD: 1.34 cm, CI: -1.58; 4.26) or 12 months (MD: 2.81 cm, CI: -0.51; 6.12) (Table\u0026nbsp;2). Adjustment and sensitivity analysis did not change the results (not shown).\u003c/p\u003e \u003cp\u003eAcross randomization (pooled data), BMI z-score was reduced by 0.11 (CI: 0.17; 0.06) at 3 months and by 0.20 (CI: 0.26; 0.14) at 12 months. There were no significant changes in waist circumference at 3 and 12 months (Table\u0026nbsp;3).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eBlood pressure\u003c/h2\u003e \u003cp\u003eNo significant differences in diastolic or systolic blood pressure were found between groups (Table\u0026nbsp;2). Across randomization, there were no changes in diastolic blood pressure at 3 or 12 months (Table\u0026nbsp;3). However, systolic blood pressure was increased after 12 months (Table\u0026nbsp;3).\u003c/p\u003e \u003cp\u003eAt baseline, 4.6% of the children and adolescents had elevated systolic blood pressure (\u0026gt;\u0026thinsp;90th percentile) and 4.6% had hypertension (\u0026gt;\u0026thinsp;95th percentile). For diastolic blood pressure, 6.9% of the cohort had elevated diastolic blood pressure and 7.5% had hypertension at baseline. There were no significant changes in the distribution of these blood pressure categories at 3 or at 12 months.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eQuality of life:\u003c/h2\u003e \u003cp\u003eThere were no differences between groups in WHO-5 well-being index after 3 or 12 months. The cohort showed an increase in WHO-5 score at 3 months, which did not sustain at 12 months (Table\u0026nbsp;3).\u003c/p\u003e \u003cp\u003eAt 3 months, the increase in HRQOL was greater in the HIIT group, with a mean difference in PedsQL child self-report, total score of 2.73 (CI: 0.01; 5.44), and a mean difference in psychosocial health score of 3.85 (CI: 0.96; 6.74) compared to the control group (Table\u0026nbsp;2). Within-group analysis showed an increase in PedsQL child self-report, total score of 5.55 (CI: 3.52; 7.58) in the HIIT group and 2.43 (CI: 0.25; 4.6) in the control group. The increase in psychosocial health score was 5.88 (CI: 3.72; 8.05) in the HIIT group and 1.42 (CI: -0.78; 3.62) in the control group.\u003c/p\u003e \u003cp\u003eAt 12 months, the control group experienced a greater increase in PedsQL child self-report physical score than the HIIT group (Table\u0026nbsp;2). The increase in physical score was 9.14 (CI: 5.51; 12.77) in the control group and 1.86 (CI: -1.14; 4.87) in the HIIT group.\u003c/p\u003e \u003cp\u003eThe PedsQL parents proxy report showed higher scores, yet not significant, in all three domains in the HIIT group at 3 months (Table\u0026nbsp;2). At 12 months, physical scores were greater in the control group compared with the HIIT group (Table\u0026nbsp;2).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eSensitivity analysis:\u003c/h2\u003e \u003cp\u003eSensitivity analysis showed a larger mean reduction in BMI z-score in boys compared to girls at 12 months of 0.16 (CI: 0.29; 0.03), corrected for baseline BMI z-score. A greater reduction in diastolic blood pressure was seen in boys compared to girls at 12 months (MD: 3.58, CI: 5.77; 1.39). No differences between sexes were found for waist circumference or systolic blood pressure.\u003c/p\u003e \u003cp\u003eFor HRQOL, the WHO-5 index for boys increased more than for girls at 12 months (MD: 7.89; CI: 1.95; 13.84). The PedsQL total (MD: 2.81; CI: 0.08; 5.53) and psychosocial domains (MD: 3.14; CI: 0.23; 6.04) increased for boys compared to girls at 3 months. These differences between sexes were also evident at 12 months in PedsQL total (MD: 4.21; CI: 0.99; 7.44), psychosocial (MD: 4.25; CI: 0.85; 7.64), and physical domains (MD: 4.87; CI: 0.73; 9.01).\u003c/p\u003e \u003cp\u003eParticipants who attended\u0026thinsp;\u0026ge;\u0026thinsp;70% of the training sessions exhibited greater PedsQL total score and physical score at 3 months than those who attended\u0026thinsp;\u0026lt;\u0026thinsp;70%. There were no other differences between these two sub-groups (Suppl.: Table\u0026nbsp;4). Sensitivity analyses for missing observations did not change the results.\u003c/p\u003e \u003cp\u003eAdjusting for COVID-19 lockdown did not affect the group differences and changes over time (data not shown). However, at 3 months, waist circumference was significantly increased among participants whose intervention was affected by COVID-19 compared to those unaffected (MD: 4.1, CI: 1.07; 7.15).\u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis two-armed randomized controlled trial aimed to examine the feasibility and efficacy of adding a 12-week HIIT program to a 12-month family-based multidisciplinary intervention.\u003c/p\u003e \u003cp\u003eWe found no differences in the primary outcome, BMI z-score, between the HIIT and control group. However, across randomization, significant reductions in BMI z-score were found at 3 months and 12 months follow-up. In addition, at 3 months HRQOL was improved in the HIIT group. Sensitivity analyses indicated that participation in HIIT resulted in lower dropout and better adherence to the lifestyle intervention.\u003c/p\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eEffects of TCOCT and exercise on BMI z-score\u003c/h2\u003e \u003cp\u003eAcross randomization, we found significant reductions in BMI z-score of 0.11 points at 3 months and 0.20 points after 12 months. In addition, boys experienced a greater reduction in BMI z-score than girls at 12 months. Consistent with these results, a cohort of Danish children admitted to a tertiary obesity clinic, showed reductions in BMI z-score of 0.30 (CI: 0.39; 0.21) in boys and 0.19 (CI: 0.25; 0.13) in girls after one year of TCOCT intervention(\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). Our results thus reinforce that multidisciplinary family-based lifestyle intervention (i.e., TCOCT) is effective in improving BMI z-score in children and adolescents with obesity, with possible greater benefit for boys. BMI z-score reductions of more than 0.25 points have been associated with improvements in cardiometabolic risk factors(\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e), but even a reduction in BMI z-score of 0.10 has been associated with health benefits among children with obesity(\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eA novel aspect of our study was to examine if adding a 3-month HIIT protocol to the TCOCT intervention would augment a reduction in BMI z-score at 3 or 12 months follow-up. We found no differences between groups. It is possible that the short duration of the HIIT intervention provided insufficient stimulus for eliciting changes in body composition. However, the lack of additive effects of HIIT is consistent with previous studies reporting only modest effects of exercise interventions on BMI z-score and waist circumference among children and adolescents with obesity(\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e). A recent study (EFRIGO) that included a 6-month supplementary HIIT intervention to a multidisciplinary lifestyle intervention showed no difference in BMI between groups. The EFIGRO study used a longer exercise intervention (22 weeks) and a larger weekly training volume (3 sessions of 90 minutes) than the present study(\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e). Taken together, these results suggest that adding exercise to multidisciplinary lifestyle interventions do not always promote greater changes in BMI z-score in children and adolescents with obesity(\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e). Notably, the EFIGRO study reported a greater reduction in hepatic fat and LDL cholesterol in the HIIT group compared with the control group (lifestyle intervention only)(\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e). Consistent with these findings, a Danish study reported metabolic improvements in 80% of the children participating in a lifestyle intervention despite no change in BMI z-score(\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e). These results suggest that multidisciplinary lifestyle intervention, including recommendations about physical activity or an exercise program, may elicit metabolic improvements, even without marked reductions in BMI z-score.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003eEffects of TCOCT and HIIT on blood pressure\u003c/h2\u003e \u003cp\u003eWe found no clinically relevant changes in blood pressure. At baseline, the majority of the participants had blood pressure within the normal range, which limits the potential for improvements in response to the interventions. Less than 8% of the participants showed signs of hypertension, which is lower than the prevalence of 16% reported by Hvidt et al. in a comparable cohort of Danish children and adolescents with obesity(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003eEffects of lifestyle interventions and HIIT on HRQOL\u003c/h2\u003e \u003cp\u003eThe physiological links between obesity-related risk behaviors, including physical inactivity and psychosocial health, are well-known and assumed to be bi-directional(\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e). Studies have shown an inverse relationship between obesity and well-being on both physical and psychosocial parameters(\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e). A novel result from the present study was that adding a 3-month HIIT program to the TCOCT protocol resulted in a greater improvement in HRQOL after 3 months, measured by PedsQL. Specifically, the HIIT group reported a greater increase in PedsQL child total score and psychosocial health score. Furthermore, the boys experienced overall greater improvement in HRQOL than the girls. These findings extend results from previous studies investigating the effects of exercise interventions on HRQOL(\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e). Goldfield et al. reported an increase in PedsQL child total score of 5.5 (CI: 1.4; 9.6) after a 22-week combined lifestyle and aerobic exercise intervention with 4 weekly training sessions compared to control groups(\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e). Together, these results emphasize the relevance of including physical activity programs as a central element in obesity treatment interventions.\u003c/p\u003e \u003cp\u003eConsistent with Goldfield et al., our sensitivity analysis showed that participants with \u0026ge;\u0026thinsp;70% attendance in HIIT sessions exhibited a greater increase in HRQOL, particularly in the physical score. This is an important finding because enjoyment and positive feelings of competence and confidence are the main psychological drivers of engagement and adherence to physical activities(\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e). In turn, this may help to improve mental health factors in this group of vulnerable children and adolescents(\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAt 12 months, we found lower levels of HRQOL in the HIIT group compared to the control group. A possible explanation is that termination of the 3-month HIIT program left many of the HIIT participants with a feeling of sadness and abandonment. This interpretation is supported by feedback from the HIIT participants and their families, who noted that they could not find a suitable exercise program to replace the HIIT. This emphasizes the importance of focusing on implementing permanent exercise programs tailored for this population.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003eHIIT intervention\u003c/h2\u003e \u003cp\u003eThe attendance rate for HIIT sessions reached 68% across the 3 months, which is high compared to reports from similar studies(\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e). In a 6-months HIIT intervention in adolescents with overweight, Herget et al. reported that the attendance rate declined from 75% in the first two months to 15% in the last three months(\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e). The dropout rate of 7.8% in our HIIT group during the first three months was lower than the dropout rate in the control group (20.5%). Notably, the dropout rate at 12 months was also lower in the HIIT group (25.5%) compared to the control group (48.2%). J\u0026oslash;rgensen et al reported a dropout rate of 43% after 12 month TCOCT protocol in a similar cohort of Danish children with obesity(\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e). Taken together, these observations indicate that participation in a tailored exercise program increases adherence to lifestyle interventions for treating obesity. In addition, our analyses revealed that a one-unit higher BMI z-score in the control group resulted in a higher RR for dropout after 3 months, which was not seen in the HIIT group. This result supports that exercise programs may be a viable option in reducing attrition in programs focused on treating obesity, particularly for children and adolescents with very high BMI z-scores.\u003c/p\u003e \u003cp\u003eChildhood is a vulnerable period of life, where psychosocial aspects are important for well-being. Adolescence is known to be the life stage with the biggest dropout in sports and physical activity programs(\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e). Psychological issues and concerns about appearance have been found to predict low adherence to training interventions in adolescents with obesity(\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e). Enjoyment, family support, creating social relations, and full participation in age-appropriate activities are important elements for children and adolescents in order to overcome challenges in relation to physical activities(\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e). The fact that our HIIT intervention was created with a playful, supportive, and non-competitive perspective through various modalities may have positively influenced adherence and dropout rates. These results support the importance of establishing tailored training interventions that embrace a safe and non-stigmatizing environment with enjoyable and motivating activities to ensure long-term adherence for children and adolescents. In addition, taking advantage of continouos HR monitoring allowed us to demonstrate that the HIIT sessions were effective in eliciting 40 minutes of moderate-to-high intensity physical activity (\u0026gt;\u0026thinsp;60% maximal HR) which constitutes a large proportion of recommended daily physical activity.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003eStrengths and limitations\u003c/h2\u003e \u003cp\u003eA limitation of the study is that we only enrolled and randomized 173 participants, which is fewer than the estimated number from the sample size calculation (N\u0026thinsp;=\u0026thinsp;202). Our study was conducted from 2020\u0026ndash;2023, and the intervention (including recruitment) was challenged by the COVID-19 pandemic and lockdown periods in the winter of 2020/2021. We experienced a general reluctance to participate in the intervention after the COVID-19 lockdown, which hindered recruitment for the study. The sensitivity analysis showed that COVID-19 did not affect the difference across intervention, but might have decreased the signal from the intervention. Notable, participants affected by COVID-19 experienced a significant increase in waist circumference at 3 months. This could have been mediated by lower levels of habitual physical activity and increased sedentary behavior during the lockdown periods, as reported in other studies(\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eA strength of our study is the randomized design, which minimized the risk of selection bias. In addition, we were able to adjust the HIIT modalities according to the childrens preferences and competences, which allowed children and adolescents with minor physical and psychological disabilities to participate. This approach embraced the great heterogeneity in the population of children and adolescents with obesity.\u003c/p\u003e \u003cp\u003eIn conclusion, our results show that it is feasible to implement 3 months of HIIT in a community-based setting tailored for children and adolescents with obesity. In fact, participation in the HIIT program appeared to promote greater adherence to the lifestyle intervention, particularly for those with severe obesity. Addition of supervised HIIT training to the TCOCT protocol did not augment the reduction in BMI z-score. However, HIIT was accompanied by greater HRQOL at 3 months, compared with the control group. Overall, the boys experienced greater effects of the intervention on BMI z-score and HRQOL. Future studies should further investigate the potential of using tailored exercise programs in community-based settings to promote greater adherence to lifestyle interventions in children and adolescents with obesity.\u003c/p\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe project was supported by Steno Diabetes Center North Denmark, Trygfonden (Grant No. 149852), Danish Regions (Grant No. \u0026nbsp;R201-A4487), A.P. Moller Foundation (Grant No. 17-L-0393), Beckett Foundation (Grant No. 17-2-1655), Svend Andersens Foundation and Memorial legatee for Carpenter J\u0026oslash;rgen Holm and wife Elisa F. Hansen (Grant No. 20094)\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWe thank iQniter (Aalborg, Denmark) for lending us the heart rate system. iQniter had no influence on the interpretation of the results.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors contributions:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCNE was responsible for designing the protocol, organising the project and HIIT intervention, collaborate with municipal co-workers and HIIT trainers, conducting clinical examinations, analysing the data and drafting the manuscript. \u0026nbsp;RGL and SH contributed as main supervisors in the design of the protocol, analysis of data, interpretation of results, and writing of the manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eETV contributed to designing and writing the project protocol, interpreting the results and writing the manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eKD contributed to the statistical analyses and interpretation as well as writing the manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eMBS contributed to the HIIT intervention, including design, heart rate monitoring, maintenance of equipment, data extraction and analysis,\u0026nbsp;and provided feedback on the manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCBC\u003csup\u003e\u0026nbsp;\u003c/sup\u003econtributed with conducting clinical examinations, data extraction and analyses (blood pressure data) as well as writing the manuscript.\u003c/p\u003e\n\u003cp\u003eTCW contributed to the design of the protocol, recruiting participants for the study, conducting clinical examinations, interpreting the results and provided feedback on the manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eJBF\u0026nbsp;contributed to the design of the protocol, conducting clinical examinations, interpreting the results and provided feedback on the manuscript.\u003c/p\u003e\n\u003cp\u003eAH contributed to the design of the protocol, supervision and support during the trial, organising parts of the clinical examinations, interpreting the results and provided feedback on the manuscript.\u003c/p\u003e\n\u003cp\u003eTS contributed to the design of the protocol, supported and organised collaboration with co-workers and leaders in the municipalities and provided feedback on the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests:\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing financial interests.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability statement:\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData is available upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eMadsen KR, Rom\u0026aacute;n JEI, Damsgaard MT, Holstein BE, Kristoffersen MJ PT et al. 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Leveraging the construct of physical literacy to promote physical activity for youth with obesity \u0026ndash; A qualitative analysis of physical therapists\u0026rsquo; perceptions. Obes Pillars. 2023;5:100054.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDaley AJ, Copeland RJ, Wright NP, Roalfe A, Wales JKH. Exercise Therapy as a Treatment for Psychopathologic Conditions in Obese and Morbidly Obese Adolescents: A Randomized, Controlled Trial. Pediatr. 2006;118(5):2126\u0026ndash;34.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlberga AS, Sigal RJ, Sweet SN, Doucette S, Russell-Mayhew S, Tulloch H, et al. Understanding low adherence to an exercise program for adolescents with obesity: the HEARTY trial. Obes Sci Pract. 2019;5(5):437\u0026ndash;48.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHerget S, Reichardt S, Grimm A, Petroff D, K\u0026auml;pplinger J, Haase M, et al. High-intensity interval training for overweight adolescents: Program acceptance of a media supported intervention and changes in body composition. Int J Environ Res Public Health. 2016;13(11).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGuthold R, Stevens GA, Riley LM, Bull FC. Global trends in insufficient physical activity among adolescents: a pooled analysis of 298 population-based surveys with 1\u0026middot;6 million participants. Lancet Child Adolesc Heal. 2020;4(1):23\u0026ndash;35.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFoster C, Moore JB, Singletary CR, Skelton JA. Physical activity and family-based obesity treatment: a review of expert recommendations on physical activity in youth. Vol. 8, Clinical obesity. 2018. p. 68\u0026ndash;79.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSchmidt SCE, Anedda B, Burchartz A, Eichsteller A, Kolb S, Nigg C, et al. Physical activity and screen time of children and adolescents before and during the COVID-19 lockdown in Germany: a natural experiment. Sci Rep. 2020;10(1):1\u0026ndash;12.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVelde G, Lubrecht J, Arayess L, Loo C, Hesselink M, Reijnders D, et al. Physical activity behaviour and screen time in Dutch children during the COVID-19 pandemic: Pre‐, during‐ and post‐school closures. Pediatr Obes. 2021;16(9):e12779\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e-n/a\u003c/span\u003e\u003cspan address=\"http://-n/a\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTable 1 to 3 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"international-journal-of-obesity","isNatureJournal":false,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"ijo","sideBox":"Learn more about [International Journal of Obesity](http://www.nature.com/ijo/)","snPcode":"41366","submissionUrl":"https://mts-ijo.nature.com/cgi-bin/main.plex","title":"International Journal of Obesity","twitterHandle":"@intjobesity","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-4223158/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4223158/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eBackground\u003c/p\u003e\n\u003cp\u003eMultidisciplinary lifestyle interventions for children and adolescents with obesity often include recommendations regarding physical activity, but no structured exercise program. We hypothesized that adding high intensity interval training (HIIT) to a multidisciplinary lifestyle intervention would improve BMI z-score (primary outcome) and health-related quality of life (HRQOL).\u003c/p\u003e\n\u003cp\u003eMethods\u003c/p\u003e\n\u003cp\u003eThis randomized controlled trial included 173 children and adolescents with obesity. Participants were allocated to a 12-months lifestyle intervention (N=83) or a 12-month lifestyle intervention accompanied by a 12-week HIIT program at intervention onset (N=90).\u003c/p\u003e\n\u003cp\u003eThe HIIT intervention consisted of three weekly sessions and included activities designed to elicit intensities \u0026gt;85% of maximal heart rate.\u003c/p\u003e\n\u003cp\u003eResults\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDropout rate was lower in HIIT compared to control at three months (7.8% vs. 20.5%) and 12 months (26.5% vs 48.2%).\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eChanges in Body mass index (BMI) z-score did not differ between HIIT and control at 3 months (Mean Difference (MD): 0.01, 95% confidence interval (CI): -0.09; 0.12, P=0.82) or 12 months (MD: 0.06, CI: -0.07; 0.19, P=0.34).\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcross randomization (pooled data), BMI z-score was reduced by 0.11 (CI: 0.17; 0.06, P\u0026lt;0.01) at 3 months and 0.20 (CI: 0.26; 0.14, P\u0026lt;0.01) at 12 months.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAt 3 months, HIIT experienced a greater increase in HRQOL, \u003c/strong\u003ewith increases \u003cstrong\u003eof 2.73 (CI: 0.01; 5.44, P=0.05) in PedsQL Child total score \u003c/strong\u003eand 3.85 (CI: 0.96; 6.74, P\u0026lt;0.01) in psychosocial health score compared to control\u003cstrong\u003e. At 12 months, PedsQL Child physical score was reduced by 6.89 (CI: 10.97; 2.83, P\u0026lt;0.01) in HIIT compared to control.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConclusion\u003c/p\u003e\n\u003cp\u003eAdding a 12-week \u0026nbsp;HIIT program did not further augment the effects of a 12-month lifestyle intervention on BMI z-score, but improved HRQOL after 3 months. Implementation of HIIT in a community-based setting was feasible and showed positive effects on adherence to the lifestyle intervention.\u003c/p\u003e","manuscriptTitle":"Feasibility and efficacy of adding high-intensity interval training to a multidisciplinary lifestyle intervention in children with obesity – a randomized controlled trial","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-19 18:59:20","doi":"10.21203/rs.3.rs-4223158/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"revise","date":"2024-07-25T14:16:51+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"This content is not available.","date":"2024-07-17T20:11:26+00:00","index":3,"fulltext":"This content is not available."},{"type":"reviewerAgreed","content":"This content is not available.","date":"2024-06-21T19:56:21+00:00","index":3,"fulltext":"This content is not available."},{"type":"editorInvitedReview","content":"This content is not available.","date":"2024-05-21T21:44:43+00:00","index":2,"fulltext":"This content is not available."},{"type":"reviewerAgreed","content":"This content is not available.","date":"2024-04-25T11:31:40+00:00","index":2,"fulltext":"This content is not available."},{"type":"reviewerAgreed","content":"This content is not available.","date":"2024-04-22T07:43:27+00:00","index":1,"fulltext":"This content is not available."},{"type":"reviewersInvited","content":"","date":"2024-04-13T06:47:51+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-04-08T16:30:09+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-04-05T12:55:58+00:00","index":"","fulltext":""},{"type":"submitted","content":"International Journal of Obesity","date":"2024-04-05T12:55:57+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"international-journal-of-obesity","isNatureJournal":false,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"ijo","sideBox":"Learn more about [International Journal of Obesity](http://www.nature.com/ijo/)","snPcode":"41366","submissionUrl":"https://mts-ijo.nature.com/cgi-bin/main.plex","title":"International Journal of Obesity","twitterHandle":"@intjobesity","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"8b2d7d3e-f0d5-498d-a68e-5e007316de44","owner":[],"postedDate":"April 19th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":30629878,"name":"Health sciences/Health care/Paediatrics"},{"id":30629879,"name":"Health sciences/Medical research/Clinical trial design/Randomized controlled trials"},{"id":30629880,"name":"Health sciences/Risk factors"}],"tags":[],"updatedAt":"2024-10-15T05:54:20+00:00","versionOfRecord":{"articleIdentity":"rs-4223158","link":"https://doi.org/10.1038/s41366-024-01645-w","journal":{"identity":"international-journal-of-obesity","isVorOnly":false,"title":"International Journal of Obesity"},"publishedOn":"2024-10-10 04:00:00","publishedOnDateReadable":"October 10th, 2024"},"versionCreatedAt":"2024-04-19 18:59:20","video":"","vorDoi":"10.1038/s41366-024-01645-w","vorDoiUrl":"https://doi.org/10.1038/s41366-024-01645-w","workflowStages":[]},"version":"v1","identity":"rs-4223158","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4223158","identity":"rs-4223158","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}