Evening Exercise Does Not Affect Sleep Health: A Systematic Review and Meta-Analysis

Evening Exercise Does Not Affect Sleep Health: A Systematic Review and Meta-Analysis | 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 Evening Exercise Does Not Affect Sleep Health: A Systematic Review and Meta-Analysis Noppachai Siranart, Nithi Tokavanich, Ponthakorn Keawkanha, Walit Sowalertrat, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4583679/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background: The relationships between exercise timing and health outcomes including anthropometric indices, metabolic markers, and sleep health have not been clearly established. To gain better insights, we performed the meta-analysis to determine the effects of morning versus evening exercise on various health outcomes. Methods: We collected studies from MEDLINE, EMBASE, and Cochrane databases from inception to March 2023 to perform a meta-analysis. Exercise is defined as performing activity at least moderate intensity. For the outcomes of interest, the mean differences (MD) were employed using a random-effects model, the generic inverse variance method of DerSimonian and Laird. Results: A total of 716 patients were analyzed from 14 studies including randomized controlled trial and observational studies. We found no significant associations between exercise timing and several health-related parameters. Specifically, the data showed no notable differences in body weight (MD: -0.12 kg [95% CI −0.81 to 0.58]) and BMI (MD: -0.07 kg/m2 [95% CI −0.46 to 0.32]) when comparing morning and evening exercise sessions. Similarly, sleep latency was not significantly affected by exercise timing (MD: -2.24 minutes [95% CI −5.83 to 1.35]). Furthermore, changes in metabolic biomarkers, including LDL (MD: -6.64 mg/dL [95% CI −20.08 to 6.79]) and HDL (MD: 0.09 mg/dL [95% CI 0 to 0.17]), were not significantly associated with the timing of exercise. Conclusion: This meta-analysis found no significant relationship between exercise timing and health outcomes including anthropometric indices, metabolic markers, and sleep health. While considered as hypothesis generating, timing of exercise should equally prune patients’ health outcomes. Health sciences/Cardiology Health sciences/Medical research exercise morning evening anthropometric indices sleep metabolic markers Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Key findings Based on our analysis, there were no statistically significant differences observed in anthropometric indices, sleep quality, and metabolic markers when considering exercise timing. These findings indicate that exercise programs can be effective in achieving desired outcomes regardless of the timing of exercise. 1. Introduction The circadian system plays a crucial role in modulating regular homeostasis, for example, appetite, sleep/wake cycles, and exercise performance [ 1 ]. In keeping with such a physiological process, prior reports suggested different responses on exercise could be varying by timing, i.e., morning and evening [ 2 , 3 ] time but there remains inconclusive. Further, in previous recommendations, the scopes have been mainly focused on optimal intensity, duration, frequency, and volume of exercise training but the effective exercise timing. [ 4 , 5 ]. Sleep patterns can be variably influenced by level of exercise intensity and timing [ 6 ]. For example, physical activity during the daytime was reported to have no implication on nighttime sleep while evening exercise increased arousal levels and compromised sleep hygiene [ 7 ]. Nevertheless, the effects of physical exercise on the subsequent nocturnal sleep are still controversial in the previous literature and several studies advocate for evening exercise [ 8 , 9 ]. The impact of exercise timing on anthropometric indices and metabolic profile remains a subject of debate. Some studies suggest that morning exercise could potentially encourage weight loss [ 10 ], while others propose that evening exercise tends to positively influence metabolic markers [ 11 , 12 ] and insulin sensitivity [ 13 ]. This apparent contradiction underscores the necessity for a more comprehensive and rigorous analysis of multiple studies to better understand the influence of exercise timing on body composition and metabolic parameters. For these reasons, we performed a systematic review and meta-analysis of the available existing reports to compare the impacts of morning versus evening exercise in general populations with respect to anthropometric indices [ 10 , 13 – 22 ], sleep parameters [ 2 , 14 , 16 – 17 , 23 ], and metabolic markers [ 14 – 15 , 17 – 20 , 22 , 24 ]. We aimed to shed further light on this topic and provide more informed guidelines for exercise timing, ultimately contributing to the promotion of overall health and well-being. 2. Methods 2.1. Literature review and search strategy Our protocol for this meta-analysis is registered with PROSPERO (International Prospective Register of Systematic Reviews; no. CRD42023426432). Our systematic review and meta-analysis adhered to the Meta-analyses Of Observational Studies in Epidemiology (MOOSE) standards and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The PRISMA checklist is provided in Supplementary 1 . We conducted a search through March 2023 in three databases: MEDLINE (via PubMed), EMBASE (via Scopus), and the Cochrane Database of Systematic Reviews. The search terms included "exercise" and ("morning" or "evening") (see Supplementary 2 ). The primary objective was to compare the effects of exercise timing (morning vs. evening) on various health outcomes, including anthropometric indices, metabolic profiles, energy balance, and sleep parameters. Additionally, we manually identified relevant research from the reference lists of the included studies. 2.2. Selection criteria Data selection and collection process were done independently by two investigators (N.S. and R.C.). Any disagreements regarding study selection were discussed and resolved by a third researcher (N.T.). To be eligible for our analysis, studies must include randomized controlled trials, cross-sectional studies, case-control studies, or cohort studies that evaluate the effects of exercise compared between morning and evening on individuals’ health. Case reports and case series were excluded from the analysis. There were no language restrictions applied. There were no restrictions on the sample size or ethnicity of the study population. Qualified studies needed to report statistical outcomes in the form of mean ± standard deviation (SD) or median (interquartile range Q1–Q3), along with p-values to determine the level of statistical significance in hypothesis testing. We used the Newcastle-Ottawa Quality Assessment Scale and the modified Newcastle-Ottawa Scale to evaluate the quality of case-control studies and the result of interest for cohort and cross-sectional studies [25]. 2.3. Definitions of exercise timing According to the literature review [10, 13-24], subjects were subdivided into morning and evening exercise groups based on the timing of the day. The exercise timing varies between research, although it may be inferred that morning (A.M.) exercise refers to physical activity performed in the early part of the day, specifically before 12:00 A.M., and evening (P.M.) exercise refers to physical activity performed in the latter part of the day, specifically after 12:00 A.M. 2.4. Definitions of the percentage of body fat, body fat mass, and body free-fat mass According to the literature review [10, 13-22], individuals were measured the percentage of body fat (BF), body fat mass (BFM) and body free-fat mass (BFFM). BF is the ratio of fat to total body weight (BW). BFM refers to the absolute quantity of fat present in the body. BFFM represents the weight of the body, excluding the fat component, indicating the overall weight of non-fat tissues such as muscle, bone, and organs. 2.5. Definitions of sleep efficiency, sleep latency, and wake after sleep onset According to the literature review [2, 14, 16-17, 23], individuals were measured sleep efficiency, sleep latency, and wake after sleep onset by polysomnography. Sleep latency refers to the time it takes for a person to fall asleep, while sleep efficiency measures the amount of time spent asleep relative to the time spent in bed, indicating the effectiveness of sleep. Wake after Sleep Onset (WASO) represents the total time spent awake after the sleep onset. 2.6. Data abstraction The following information was extracted from each study: 2.6.1. Basic information of the literature: the title and year of the study, name of the first author, publication year, and the country where the study was conducted. 2.6.2. Patient baseline characteristics, demographic data, types of exercises, duration of exercise, the definition of morning and evening period, and follow-up time. 2.6.3. Outcomes: a. the body composition indices, including BW, body mass index (BMI), BF, BFM, BFFM, and waist circumference (WC). b. metabolic profiles which are total cholesterol (TC) level, high-density lipoprotein (HDL) level, low-density lipoprotein (LDL) level, and triglyceride (TG) level. c. the sleep parameters which are measured by polysomnography, including sleep duration, sleep efficiency, sleep latency, and WASO. 2.7. Statistical analysis We used statistical conversion methods to standardize our synthesis because the variations in data reporting across studies. Means and standard deviations were selected for further statistical analysis as previously described in studies. [26, 27] Random-effects model by DerSimonian and Laird’s technique [28] was used to calculate adjusted point estimates from each study (p 25%) [29]. We used Cochran's Q test to investigate and quantify the degree of heterogeneity in the prevalence estimates across studies. To explore the source of heterogeneity, we performed a meta-regression. We assessed publication bias using a funnel plot and Egger's test. [30] All analyses were conducted using R software version 3.6.3 (R Foundation for Statistical Computing, Vienna, Austria) 3. Results After screening duplicated studies, our search approach yielded 6,209 articles. We excluded 5,102 studies that were either case reports, case series, review articles, in vitro studies, animal studies, or interventional studies after screening their abstracts. Subsequently, we manually added 3 studies from the references of the article due to the same outcomes of interest. We reviewed the full text of 47 studies, out of which 33 articles were later excluded due to either a lack of a target population or failure to report outcomes of interest. Consequently, our final analysis included 12 randomized controlled trials and 2 observational prospective cohort studies with 716 individuals who underwent exercise courses. These 14 studies were further categorized into 3 groups of interesting outcomes: 11 articles with anthropometric indices, 8 articles with metabolic profiles, and 5 articles with sleep parameters. Figure 1 illustrates the inclusion and exclusion process of the literature review, while Tables 1-3 provide information on the characteristics and quality assessment of the included studies. 3.1. Effects of exercise time on anthropometric indices A total of eleven studies comprising 378 participants were analyzed to investigate the effects of exercise timing on anthropometric outcomes. Our results indicated that exercise timing did not show a significant association with changes in BW (MD: -0.12 kg, 95% confidence interval (CI) -0.81 to 0.58, I2 = 99%), BMI (MD: -0.07 kg/m2, 95% CI -0.46 to 0.32, I2 = 99%), BFM (MD: 0.18 kg, 95% CI -1.13 to 1.49, I2 = 100%), BFFM (MD: 0.06 kg, 95% CI -0.35 to 0.46, I2 = 98%), BF (MD: 0.08%, 95% CI -0.61 to 0.44, I2 = 100%), and WC (MD: 0.18 inches, 95% CI -1.13 to 1.49, I2 = 100%) when comparing between morning and evening, as shown in Figure 2 . 3.2. Effects of exercise time on metabolic profiles and energy balance Of four studies with a total of 294 patients, our meta-analysis showed that exercise timing did not have significant effects on metabolic profiles ( Figure 3 and 4 ). Specifically, there was no significant association between exercise timing and LDL (MD: -6.64 mg/dL [95% CI −20.08 to 6.79, I2 = 100%]), HDL (MD: 0.09 mg/dL [95% CI 0 to 0.17, I2 = 99%]), TG (MD: -0.11 mg/dL [95% CI −0.43 to 0.21, I2 = 100%]), and TC (MD: 0.38 mg/dL [95% CI −0.20 to 0.95, I2 = 100%]). Additionally, there was no significant effect of exercise timing on total daily energy expenditure (TDEE) (MD: -32.87 kcal/day [95% CI −226.91 to 161.16, I2 = 100%]), and energy intake (EI) (MD: 76.03 kcal/day [95% CI −107.92 to 259.97, I2 = 100%]). 3.3. Effects of exercise time on sleep parameters A total of five studies involving 168 participants were included in the meta-analysis to investigate the effect of exercise timing on sleep outcomes. The analysis revealed that exercise timing was not significantly associated with changes in sleep latency (MD: -2.24 minutes [95% CI −5.83 to 1.35, I2 = 99%]), sleep efficiency (MD: -0.17% [95% CI −2.23 to 1.89, I2 = 99%]), and WASO (MD: 0.58 minutes [95% CI −12.44 to 13.60, I2 = 100%]), as demonstrated in Figure 5 . 3.4. Evaluation of publication bias Due to the limited amount of available data, the statistical power of the test was insufficient to discern between chance occurrences and actual asymmetry. As a result, a funnel plot could not be generated. In terms of the correlations between exercise timing and outcomes, the application of Egger's regression asymmetry analysis revealed no evidence of publication bias as shown in Supplementary 3 . 4. Discussion Our study is the first meta-analysis to reveal the effects of exercise timing on various health outcomes. The results of this study demonstrated that there was no statistical significance on the effects of exercise timing on individuals’ health outcomes including anthropometric outcomes, metabolic markers, and sleep parameters. While our meta-analysis found no statistically significant difference in BW, BMI, BFM, and BFFM between the morning and evening exercise groups, some previous studies have reported conflicting outcomes. For the studies supporting morning exercise, Alizadeh et al. [ 10 ] found greater reductions in BW (MD: -1.55 vs -0.6 kg; p = 0.04), BMI, and BFM in the morning exercise group compared to the evening exercise group after a 6-week supervised aerobic exercise program. Exercising in the morning may result in a stronger metabolic response due to time-dependent molecular signaling, leading to higher utilization of carbohydrates and fat degradation. [ 31 ] This could explain why some studies have shown more significant weight loss in individuals who exercise in the morning. In contrast, Mancilla et al. [ 13 ] found a greater reduction of fat mass in the evening exercise group (MD: -1.2 vs -0.2 kg; p = 0.03) after 12 weeks of tightly controlled progressive exercise. Additionally, Di Blasio et al. [ 22 ] showed a greater reduction of BFM in the evening exercise group than the morning exercise group (MD: -1.71 vs -0.24 kg; p = 0.037) after a 3-month partially supervised walking intervention. This favorable effect of evening exercise is supported by a growing body of evidence. The higher levels of interleukin-6 (IL-6), growth hormone, and blood catecholamines during evening exercise lead to greater lipolysis. [ 32 , 33 ] These may suggest evening exercise has more effective in health outcomes which can reduce body weight and BMI. From the conflicting results, it might be implied that there may be differences in metabolic responses in individuals depending on the timing of exercise and lifestyles and further research on the effect of exercise timing on various metabolic responses is needed to fully elucidate this effect. Our findings align with those of a 12-week self-paced aerobic exercise intervention conducted by Brooker et al. [ 15 ], which involved 250 minutes of exercise per week and showed no significant difference in lipid levels between morning and evening exercise groups. Nevertheless, several studies have indicated that evening exercise may result in more substantial reductions in LDL levels and triglyceride levels compared to morning exercise [ 34 , 35 ]. These differences may be due to the diurnal variation in cholesterol and triglyceride biosynthesis, which is typically higher during the night. As such, it can be hypothesized that evening exercise might exert a more pronounced influence on lipid metabolism, paralleling the effects of statins [ 36 ]. On the contrary, based on available studies, the relationship between timing of exercise and metabolic markers remains unclear. In terms of energy balance, our study resonates with previous research by Ellis et al. [ 18 ] and Creasy et al. [ 14 ], which found no significant alterations in TDEE or EI between morning and evening exercise groups. However, both studies observed a trend toward an increase in TDEE and EI in the morning exercise group, aligning with the exercise prescription. This suggests that our bodies respond more positively and exhibit diminished responses to evening exercise. One possible mechanism is that morning exercise induces phase advance in individuals with circadian misalignment and promotes the light-dark cycle. [ 37 ] However, it is important to note that both studies had small sample sizes, and the study by Creasy et al. [ 14 ] was a pilot study which has no control group, making it difficult to determine if the changes observed were due to the exercise intervention or other factors. Our study found no statistically significant differences in sleep latency, sleep efficacy, and WASO between individuals who exercised in the morning versus those who exercised in the evening. These results are consistent with several recent studies [ 2 , 16 , 17 ] that also found no significant differences in sleep outcomes between the two exercise timing groups. Notably, a study by Soel et al. [ 23 ] reported improvements in sleep latency in both the morning and evening exercise groups, while Teo et al. [ 17 ] found improvements in sleep quality after exercise in both groups. It's important to recognize that the effects of exercise timing on the sleep-wake cycle can differ depending on an individual's chronotype, post-exercise duration before bedtime, and exercise environment. Morning exercise may delay sleep onset in those with an earlier chronotype, while evening exercise may advance sleep onset. [ 37 ] For individuals with a late chronotype, both morning and evening exercise may advance sleep, potentially due to changes in melatonin secretion. Thus, personalized exercise prescriptions that consider an individual's chronotype and other sleep-related factors may be beneficial in improving sleep outcomes through exercise. [ 38 ] There are several limitations to this study. First, some of the included studies are observational studies in which residual biases are inevitable. Further, a causal relationship between health outcomes and exercise at different timings cannot be established but rather considered as hypothesis generating. Second, significant heterogeneity was observed in our analyses. Several reasons may account for disparities in study design, methods of exercise, definitions of the timing of exercise, and follow-up times. However, only exercise with at least moderate intensity was included per our inclusion criteria to improve study homogenization. Moreover, we used a random effects model in our analysis. Lastly, the included studies in this analysis contain relatively small sample sizes, potentially underpowering to detect differences between the two groups. However, this research at minimum provides the most updated insights on our current understanding of the impacts of timing on exercise in a tangible manner. Future studies could focus on the long-term effects and sustainability of the intervention. While this study examined short-term outcomes, it is essential to understand whether the positive effects persist over an extended period. Longitudinal studies can help determine whether the improvements in physical well-being are maintained over time or if there is a need for ongoing support and reinforcement. Understanding the long-term implications of the intervention is vital for designing effective interventions that lead to lasting changes in individuals' physical well-being. In conclusion, our study suggests that there is no significant difference between the outcomes of morning and evening exercise, but there is a significant difference in anthropometric outcomes pre- and post-exercise. Therefore, the timing of exercise may not be as important as the act of exercising itself. Regular exercise, regardless of the time of day, can positively change body composition and overall health. It is important to note that individual preferences and schedules may play a role in determining the optimal time for exercise. Further research is necessary to elucidate the underlying mechanisms by which exercise timing influences diverse health outcomes. Additionally, conducting large-scale randomized controlled trials could be beneficial in detecting any significant differences between the two groups. Abbreviations AM: Ante Meridiem (Before Midday) BF: percentage of Body Fat BFM: Body Fat Mass BFFM: Body Fat Free Mass BMI: Body Mass Index BW: Body Weight CI: Confidence Interval EI: Energy Intake HDL: High-Density Lipoprotein IL-6: Interleukin-6 LDL: Low-Density Lipoprotein MD: Mean Difference MOOSE: Meta-analysis Of Observational Studies in Epidemiology PM: Post Meridiem (After Midday) PRISMA: Preferred Reporting Items for Systematic reviews and Meta-Analyses SD: Standard Deviation TC: Total Cholesterol TDEE: Total Daily Energy Expenditure TG: Triglycerides WASO: Wake After Sleep Onset Declarations Funding: None Conflict of interest statement for all authors: We do not have any financial or non-financial potential conflicts of interest. Authors’ contributions: All authors had access to the data and a role in writing the manuscript. Data availability The datasets used and analysed during the current study available from the corresponding author on reasonable request. 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(2019). Time of Exercise Specifies the Impact on Muscle Metabolic Pathways and Systemic Energy Homeostasis. Cell Metab, 30(1), 92-110.e114. https://doi.org/10.1016/j.cmet.2019.03.013 Zouhal, H., Jacob, C., Delamarche, P., & Gratas-Delamarche, A. (2008). Catecholamines and the effects of exercise, training and gender. Sports Med, 38(5), 401-423. https://doi.org/10.2165/00007256-200838050-00004 Thomas, G. A., Kraemer, W. J., Comstock, B. A., Dunn-Lewis, C., Maresh, C. M., & Volek, J. S. (2013). Obesity, growth hormone and exercise. Sports Med, 43(9), 839-849. https://doi.org/10.1007/s40279-013-0064-7 Bremner, W. F., Sothern, R. B., Kanabrocki, E. L., Ryan, M., McCormick, J. B., Dawson, S., Connors, E. S., Rothschild, R., Third, J. L., Vahed, S., Nemchausky, B. M., Shirazi, P., & Olwin, J. H. (2000). Relation between circadian patterns in levels of circulating lipoprotein(a), fibrinogen, platelets, and related lipid variables in men. Am Heart J, 139(1 Pt 1), 164-173. https://doi.org/10.1016/s0002-8703(00)90324-7 Poggiogalle, E., Jamshed, H., & Peterson, C. M. (2018). Circadian regulation of glucose, lipid, and energy metabolism in humans. Metabolism, 84, 11-27. https://doi.org/10.1016/j.metabol.2017.11.017 Saito, Y., Yoshida, S., Nakaya, N., Hata, Y., & Goto, Y. (1991). Comparison between morning and evening doses of simvastatin in hyperlipidemic subjects. A double-blind comparative study. Arterioscler Thromb, 11(4), 816-826. https://doi.org/10.1161/01.atv.11.4.816 Thomas, J. M., Kern, P. A., Bush, H. M., McQuerry, K. J., Black, W. S., Clasey, J. L., & Pendergast, J. S. (2020). Circadian rhythm phase shifts caused by timed exercise vary with chronotype. JCI Insight, 5(3). https://doi.org/10.1172/jci.insight.134270 Vitale, J. A., & Weydahl, A. (2017). Chronotype, Physical Activity, and Sport Performance: A Systematic Review. Sports Med, 47(9), 1859-1868. https://doi.org/10.1007/s40279-017-0741-z Tables Tables 1 to 3 are available in the Supplementary Files section Additional Declarations No competing interests reported. Supplementary Files AMvsPMexerciseSupplementary1.docx AMvsPMexerciseSupplementary2.docx AMvsPMexerciseSupplementary3.docx Tables.docx Cite Share Download PDF Status: Posted Version 1 posted 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-4583679","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":334852033,"identity":"440075cb-e193-4f24-9530-4864c0a3fc60","order_by":0,"name":"Noppachai Siranart","email":"","orcid":"","institution":"King Chulalongkorn Memorial Hospital, Chulalongkorn University","correspondingAuthor":false,"prefix":"","firstName":"Noppachai","middleName":"","lastName":"Siranart","suffix":""},{"id":334852034,"identity":"ef8e1217-9ed9-40f5-a7ba-a4a73e5505c8","order_by":1,"name":"Nithi Tokavanich","email":"","orcid":"","institution":"Michigan State University","correspondingAuthor":false,"prefix":"","firstName":"Nithi","middleName":"","lastName":"Tokavanich","suffix":""},{"id":334852035,"identity":"26a13942-671f-469c-b2ee-d6f5ec565a9e","order_by":2,"name":"Ponthakorn Keawkanha","email":"","orcid":"","institution":"King Chulalongkorn Memorial Hospital, Chulalongkorn University","correspondingAuthor":false,"prefix":"","firstName":"Ponthakorn","middleName":"","lastName":"Keawkanha","suffix":""},{"id":334852036,"identity":"0a9fee79-071c-42fc-bceb-2bd014251a65","order_by":3,"name":"Walit Sowalertrat","email":"","orcid":"","institution":"King Chulalongkorn Memorial Hospital, Chulalongkorn University","correspondingAuthor":false,"prefix":"","firstName":"Walit","middleName":"","lastName":"Sowalertrat","suffix":""},{"id":334852037,"identity":"2af1ac9e-4b51-4373-a30a-e030de20cf5d","order_by":4,"name":"Patavee Pajareya","email":"","orcid":"","institution":"King Chulalongkorn Memorial Hospital, Chulalongkorn University","correspondingAuthor":false,"prefix":"","firstName":"Patavee","middleName":"","lastName":"Pajareya","suffix":""},{"id":334852038,"identity":"9b9a8b0b-b4a1-4d93-ba50-9f021fc3fdb4","order_by":5,"name":"Setthawut Joensahakij","email":"","orcid":"","institution":"King Chulalongkorn Memorial Hospital, Chulalongkorn University","correspondingAuthor":false,"prefix":"","firstName":"Setthawut","middleName":"","lastName":"Joensahakij","suffix":""},{"id":334852039,"identity":"27de668b-2a87-4799-b88d-da551739be75","order_by":6,"name":"Narut Prasitlumkum","email":"","orcid":"","institution":"University of California Riverside","correspondingAuthor":false,"prefix":"","firstName":"Narut","middleName":"","lastName":"Prasitlumkum","suffix":""},{"id":334852040,"identity":"3579d1e4-7472-4fcd-9edc-2d7cd4cb4440","order_by":7,"name":"Leenhapong Navaravong","email":"","orcid":"","institution":"University of Utah School of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Leenhapong","middleName":"","lastName":"Navaravong","suffix":""},{"id":334852041,"identity":"51633dcc-997d-484b-a274-5c5b20cfa1d7","order_by":8,"name":"Wisit Cheungpasitporn","email":"","orcid":"","institution":"Mayo Clinic","correspondingAuthor":false,"prefix":"","firstName":"Wisit","middleName":"","lastName":"Cheungpasitporn","suffix":""},{"id":334852042,"identity":"734ad0ba-6ecf-4776-a51b-828da36267f9","order_by":9,"name":"Ronpichai Chokesuwattanaskul","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA5klEQVRIiWNgGAWjYDCCA2BSgsGAgbGB4QOQycZOihbGGSAtzMRpYQBqYWBg5gGxCGnhu3324ePCHRby5uyHGz/b/Nomz8fMwPjhYw5uLZLn0o2NZ56RMNzZk9gsndt327CNmYFZcuY23FoMzrCxSfO2SSQYHEhsY87tuc0I1MLGzEuUlvMP25gte27bk6DlBtAWhh+3EwlqkTzDxmzMC/TLhhsPmyV7G24ntzEzNuP1C98ZNsbHvDvq5A3Opz/88OPPbdv57c0HP3zEowUMgPEOZbShcInRwvCHsOJRMApGwSgYeQAAv65NTBtD3CcAAAAASUVORK5CYII=","orcid":"","institution":"King Chulalongkorn Memorial Hospital, Chulalongkorn University","correspondingAuthor":true,"prefix":"","firstName":"Ronpichai","middleName":"","lastName":"Chokesuwattanaskul","suffix":""}],"badges":[],"createdAt":"2024-06-14 18:26:11","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4583679/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4583679/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":62184647,"identity":"a01e5436-644d-479f-9242-a0803dd17ded","added_by":"auto","created_at":"2024-08-10 11:46:05","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":34960,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePRISMA Flow Diagram of the Search and Selection Process. \u003c/strong\u003eThe diagram details the number of records identified, screened, assessed for eligibility, and included in the meta-analysis. The diagram also shows the reasons for exclusion at each stage of the selection process.\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-4583679/v1/066c52536bf12d879502d261.png"},{"id":62184649,"identity":"95f1d3bc-252d-4c46-ad05-6426786d764a","added_by":"auto","created_at":"2024-08-10 11:46:05","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":6475996,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eForest Plots of the Effects of Exercise Timing on Anthropometric Indices.\u003c/strong\u003e The indices include (A), BMI (B), body fat mass (C), fat-free mass (D), body fat percentage (E), and waist circumference (F). Square markers represent mean differences (MD) and 95% confidence intervals (CI), with marker size indicating study weight in a random-effects meta-analysis. Diamond markers show overall MDs and 95% CIs.\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-4583679/v1/94243d32e7db53e5c26556f4.png"},{"id":62184653,"identity":"bb829f9d-2469-454a-a39d-03e02c517cb4","added_by":"auto","created_at":"2024-08-10 11:46:05","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":3336297,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eForest Plots of the Effects of Exercise Timing on Metabolic Profile.\u003c/strong\u003e The metabolic markers include LDL (A), HDL (B), TG (C), and TC (D). Square markers represent mean differences (MD) and 95% confidence intervals (CI), with marker size indicating study weight in a random-effects meta-analysis. Diamond markers show overall MDs and 95% CIs.\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-4583679/v1/e0d7696b15b3a6111a17ee16.png"},{"id":62184655,"identity":"d51c4356-f626-4ae8-a8c0-e79fad359242","added_by":"auto","created_at":"2024-08-10 11:46:05","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1533044,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eForest Plots of the Effects of Exercise Timing on Energy Balance. \u003c/strong\u003eThe energy-related outcomes include TDEE (A), and EI (B). Square markers represent mean differences (MD) and 95% confidence intervals (CI), with marker size indicating study weight in a random-effects meta-analysis. Diamond markers show overall MDs and 95% CIs.\u003c/p\u003e","description":"","filename":"Figure4.png","url":"https://assets-eu.researchsquare.com/files/rs-4583679/v1/f53c588b3d5a20c6edafa1c7.png"},{"id":62184654,"identity":"cc1ec2ff-6bf2-4809-ad72-14ca4dd4a33b","added_by":"auto","created_at":"2024-08-10 11:46:05","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":2342238,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eForest Plots of the Effects of Exercise Timing on Sleep Parameters. \u003c/strong\u003eThe sleep-related parameters include sleep latency (A), sleep efficiency (B), and WASO (C). Square markers represent mean differences (MD) and 95% confidence intervals (CI), with marker size indicating study weight in a random-effects meta-analysis. Diamond markers show overall MDs and 95% CIs.\u003c/p\u003e","description":"","filename":"Figure5.png","url":"https://assets-eu.researchsquare.com/files/rs-4583679/v1/2d8ad12084a7a9cad56c8b92.png"},{"id":62928110,"identity":"b0ab8b7d-679a-46a1-89b9-66f62a615499","added_by":"auto","created_at":"2024-08-21 07:11:44","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":12748241,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4583679/v1/821ea34e-73ac-43e6-af75-c9ca7a63ce43.pdf"},{"id":62186044,"identity":"6f034123-172c-450f-b736-94e09838d58f","added_by":"auto","created_at":"2024-08-10 12:02:05","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":33399,"visible":true,"origin":"","legend":"","description":"","filename":"AMvsPMexerciseSupplementary1.docx","url":"https://assets-eu.researchsquare.com/files/rs-4583679/v1/07c71be2ef41c87ac1ee37aa.docx"},{"id":62184648,"identity":"d1b36e49-43b4-4e1f-a61a-0a0255c70f06","added_by":"auto","created_at":"2024-08-10 11:46:05","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":13860,"visible":true,"origin":"","legend":"","description":"","filename":"AMvsPMexerciseSupplementary2.docx","url":"https://assets-eu.researchsquare.com/files/rs-4583679/v1/4eca1cfce2f8fe79246c32ff.docx"},{"id":62185494,"identity":"07ab596d-e449-4fe7-946c-756623cef886","added_by":"auto","created_at":"2024-08-10 11:54:05","extension":"docx","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":16859,"visible":true,"origin":"","legend":"","description":"","filename":"AMvsPMexerciseSupplementary3.docx","url":"https://assets-eu.researchsquare.com/files/rs-4583679/v1/3a90cda5017bbb70595b2d79.docx"},{"id":62184652,"identity":"bb268cf4-1ed9-42c6-ac4c-785603db8ea1","added_by":"auto","created_at":"2024-08-10 11:46:05","extension":"docx","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":43385,"visible":true,"origin":"","legend":"","description":"","filename":"Tables.docx","url":"https://assets-eu.researchsquare.com/files/rs-4583679/v1/011951c4696c4701c1c731b8.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Evening Exercise Does Not Affect Sleep Health: A Systematic Review and Meta-Analysis","fulltext":[{"header":"Key findings","content":"\u003cp\u003eBased on our analysis, there were no statistically significant differences observed in anthropometric indices, sleep quality, and metabolic markers when considering exercise timing. These findings indicate that exercise programs can be effective in achieving desired outcomes regardless of the timing of exercise.\u003c/p\u003e"},{"header":"1. Introduction","content":"\u003cp\u003eThe circadian system plays a crucial role in modulating regular homeostasis, for example, appetite, sleep/wake cycles, and exercise performance [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. In keeping with such a physiological process, prior reports suggested different responses on exercise could be varying by timing, i.e., morning and evening [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] time but there remains inconclusive. Further, in previous recommendations, the scopes have been mainly focused on optimal intensity, duration, frequency, and volume of exercise training but the effective exercise timing. [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSleep patterns can be variably influenced by level of exercise intensity and timing [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. For example, physical activity during the daytime was reported to have no implication on nighttime sleep while evening exercise increased arousal levels and compromised sleep hygiene [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Nevertheless, the effects of physical exercise on the subsequent nocturnal sleep are still controversial in the previous literature and several studies advocate for evening exercise [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe impact of exercise timing on anthropometric indices and metabolic profile remains a subject of debate. Some studies suggest that morning exercise could potentially encourage weight loss [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], while others propose that evening exercise tends to positively influence metabolic markers [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] and insulin sensitivity [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. This apparent contradiction underscores the necessity for a more comprehensive and rigorous analysis of multiple studies to better understand the influence of exercise timing on body composition and metabolic parameters.\u003c/p\u003e \u003cp\u003eFor these reasons, we performed a systematic review and meta-analysis of the available existing reports to compare the impacts of morning versus evening exercise in general populations with respect to anthropometric indices [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan additionalcitationids=\"CR14 CR15 CR16 CR17 CR18 CR19 CR20 CR21\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], sleep parameters [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], and metabolic markers [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan additionalcitationids=\"CR18 CR19\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. We aimed to shed further light on this topic and provide more informed guidelines for exercise timing, ultimately contributing to the promotion of overall health and well-being.\u003c/p\u003e"},{"header":"2. Methods","content":"\u003cp\u003e2.1. \u003cem\u003eLiterature review and search strategy\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eOur protocol for this meta-analysis is registered with PROSPERO (International Prospective Register of Systematic Reviews; no. CRD42023426432). Our systematic review and meta-analysis adhered to the Meta-analyses Of Observational Studies in Epidemiology (MOOSE) standards and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The PRISMA checklist is provided in \u003cstrong\u003e\u003cu\u003eSupplementary 1\u003c/u\u003e\u003c/strong\u003e.\u003c/p\u003e\n\u003cp\u003eWe conducted a search through March 2023 in three databases: MEDLINE (via PubMed), EMBASE (via Scopus), and the Cochrane Database of Systematic Reviews. The search terms included \u0026quot;exercise\u0026quot; and (\u0026quot;morning\u0026quot; or \u0026quot;evening\u0026quot;) (see \u003cstrong\u003e\u003cu\u003eSupplementary 2\u003c/u\u003e\u003c/strong\u003e). The primary objective was to compare the effects of exercise timing (morning vs. evening) on various health outcomes, including anthropometric indices, metabolic profiles, energy balance, and sleep parameters. Additionally, we manually identified relevant research from the reference lists of the included studies.\u003c/p\u003e\n\u003cp\u003e2.2. \u003cem\u003eSelection criteria\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eData selection and collection process were done independently by two investigators (N.S. and R.C.). Any disagreements regarding study selection were discussed and resolved by a third researcher (N.T.). To be eligible for our analysis, studies must include randomized controlled trials, cross-sectional studies, case-control studies, or cohort studies that evaluate the effects of exercise compared between morning and evening on individuals\u0026rsquo; health. Case reports and case series were excluded from the analysis. There were no language restrictions applied. \u003c/p\u003e\n\u003cp\u003eThere were no restrictions on the sample size or ethnicity of the study population. Qualified studies needed to report statistical outcomes in the form of mean \u0026plusmn; standard deviation (SD) or median (interquartile range Q1\u0026ndash;Q3), along with p-values to determine the level of statistical significance in hypothesis testing. We used the Newcastle-Ottawa Quality Assessment Scale and the modified Newcastle-Ottawa Scale to evaluate the quality of case-control studies and the result of interest for cohort and cross-sectional studies [25].\u003c/p\u003e\n\u003cp\u003e2.3. \u003cem\u003eDefinitions of exercise timing\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eAccording to the literature review [10, 13-24], subjects were subdivided into morning and evening exercise groups based on the timing of the day. The exercise timing varies between research, although it may be inferred that morning (A.M.) exercise refers to physical activity performed in the early part of the day, specifically before 12:00 A.M., and evening (P.M.) exercise refers to physical activity performed in the latter part of the day, specifically after 12:00 A.M.\u003c/p\u003e\n\u003cp\u003e2.4. \u003cem\u003eDefinitions of the percentage of body fat, body fat mass, and body free-fat mass\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eAccording to the literature review [10, 13-22], individuals were measured the percentage of body fat (BF), body fat mass (BFM) and body free-fat mass (BFFM). BF is the ratio of fat to total body weight (BW). BFM refers to the absolute quantity of fat present in the body. BFFM represents the weight of the body, excluding the fat component, indicating the overall weight of non-fat tissues such as muscle, bone, and organs.\u003c/p\u003e\n\u003cp\u003e2.5. \u003cem\u003eDefinitions of sleep efficiency, sleep latency, and wake after sleep onset\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eAccording to the literature review [2, 14, 16-17, 23], individuals were measured sleep efficiency, sleep latency, and wake after sleep onset by polysomnography. Sleep latency refers to the time it takes for a person to fall asleep, while sleep efficiency measures the amount of time spent asleep relative to the time spent in bed, indicating the effectiveness of sleep. Wake after Sleep Onset (WASO) represents the total time spent awake after the sleep onset.\u003c/p\u003e\n\u003cp\u003e2.6. \u003cem\u003eData abstraction\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe following information was extracted from each study:\u003c/p\u003e\n\u003cp\u003e2.6.1. Basic information of the literature: the title and year of the study, name of the first author, publication year, and the country where the study was conducted.\u003c/p\u003e\n\u003cp\u003e2.6.2. Patient baseline characteristics, demographic data, types of exercises, duration of exercise, the definition of morning and evening period, and follow-up time.\u003c/p\u003e\n\u003cp\u003e2.6.3. Outcomes: \u003c/p\u003e\n\u003cp\u003ea. the body composition indices, including BW, body mass index (BMI), BF, BFM, BFFM, and waist circumference (WC).\u003c/p\u003e\n\u003cp\u003eb. metabolic profiles which are total cholesterol (TC) level, high-density lipoprotein (HDL) level, low-density lipoprotein (LDL) level, and triglyceride (TG) level.\u003c/p\u003e\n\u003cp\u003ec. the sleep parameters which are measured by polysomnography, including sleep duration, sleep efficiency, sleep latency, and WASO.\u003c/p\u003e\n\u003cp\u003e2.7. \u003cem\u003eStatistical analysis\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eWe used statistical conversion methods to standardize our synthesis because the variations in data reporting across studies. Means and standard deviations were selected for further statistical analysis as previously described in studies. [26, 27] Random-effects model by DerSimonian and Laird\u0026rsquo;s technique [28] was used to calculate adjusted point estimates from each study (p \u0026lt; 0.1 or I2 \u0026gt; 25%) [29]. We used Cochran\u0026apos;s Q test to investigate and quantify the degree of heterogeneity in the prevalence estimates across studies. To explore the source of heterogeneity, we performed a meta-regression. We assessed publication bias using a funnel plot and Egger\u0026apos;s test. [30] All analyses were conducted using R software version 3.6.3 (R Foundation for Statistical Computing, Vienna, Austria)\u003c/p\u003e"},{"header":"3. Results","content":"\u003cp\u003eAfter screening duplicated studies, our search approach yielded 6,209 articles. We excluded 5,102 studies that were either case reports, case series, review articles, in vitro studies, animal studies, or interventional studies after screening their abstracts. Subsequently, we manually added 3 studies from the references of the article due to the same outcomes of interest. We reviewed the full text of 47 studies, out of which 33 articles were later excluded due to either a lack of a target population or failure to report outcomes of interest. Consequently, our final analysis included 12 randomized controlled trials and 2 observational prospective cohort studies with 716 individuals who underwent exercise courses. These 14 studies were further categorized into 3 groups of interesting outcomes: 11 articles with anthropometric indices, 8 articles with metabolic profiles, and 5 articles with sleep parameters. \u003cstrong\u003e\u003cu\u003eFigure 1\u003c/u\u003e\u003c/strong\u003e illustrates the inclusion and exclusion process of the literature review, while \u003cstrong\u003e\u003cu\u003eTables 1-3\u003c/u\u003e\u003c/strong\u003e provide information on the characteristics and quality assessment of the included studies.\u003c/p\u003e\n\u003cp\u003e3.1.\u0026nbsp; \u003cem\u003eEffects of exercise time on anthropometric indices\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eA total of eleven studies comprising 378 participants were analyzed to investigate the effects of exercise timing on anthropometric outcomes. Our results indicated that exercise timing did not show a significant association with changes in BW (MD: -0.12 kg, 95% confidence interval (CI) -0.81 to 0.58, I2 = 99%), BMI (MD: -0.07 kg/m2, 95% CI -0.46 to 0.32, I2 = 99%), BFM (MD: 0.18 kg, 95% CI -1.13 to 1.49, I2 = 100%), BFFM (MD: 0.06 kg, 95% CI -0.35 to 0.46, I2 = 98%), BF (MD: 0.08%, 95% CI -0.61 to 0.44, I2 = 100%), and WC (MD: 0.18 inches, 95% CI -1.13 to 1.49, I2 = 100%) when comparing between morning and evening, as shown in \u003cstrong\u003e\u003cu\u003eFigure 2\u003c/u\u003e\u003c/strong\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.2.\u0026nbsp; \u0026nbsp;\u0026nbsp;Effects of exercise time on metabolic profiles and energy balance\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eOf four studies with a total of 294 patients, our meta-analysis showed that exercise timing did not have significant effects on metabolic profiles (\u003cstrong\u003e\u003cu\u003eFigure 3 and 4\u003c/u\u003e\u003c/strong\u003e). Specifically, there was no significant association between exercise timing and LDL (MD: -6.64 mg/dL [95% CI \u0026minus;20.08 to 6.79, I2 = 100%]), HDL (MD: 0.09 mg/dL [95% CI 0 to 0.17, I2 = 99%]), TG (MD: -0.11 mg/dL [95% CI \u0026minus;0.43 to 0.21, I2 = 100%]), and TC (MD: 0.38 mg/dL [95% CI \u0026minus;0.20 to 0.95, I2 = 100%]). Additionally, there was no significant effect of exercise timing on total daily energy expenditure (TDEE) (MD: -32.87 kcal/day [95% CI \u0026minus;226.91 to 161.16, I2 = 100%]), and energy intake (EI) (MD: 76.03 kcal/day [95% CI \u0026minus;107.92 to 259.97, I2 = 100%]).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.3.\u0026nbsp;Effects of exercise time on sleep parameters\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eA total of five studies involving 168 participants were included in the meta-analysis to investigate the effect of exercise timing on sleep outcomes. The analysis revealed that exercise timing was not significantly associated with changes in sleep latency (MD: -2.24 minutes [95% CI \u0026minus;5.83 to 1.35, I2 = 99%]), sleep efficiency (MD: -0.17% [95% CI \u0026minus;2.23 to 1.89, I2 = 99%]), and WASO (MD: 0.58 minutes [95% CI \u0026minus;12.44 to 13.60, I2 = 100%]), as demonstrated in \u003cstrong\u003e\u003cu\u003eFigure 5\u003c/u\u003e\u003c/strong\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.4.\u0026nbsp;Evaluation of publication bias\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eDue to the limited amount of available data, the statistical power of the test was insufficient to discern between chance occurrences and actual asymmetry. As a result, a funnel plot could not be generated. In terms of the correlations between exercise timing and outcomes, the application of Egger\u0026apos;s regression asymmetry analysis revealed no evidence of publication bias as shown in\u0026nbsp;\u003cstrong\u003e\u003cu\u003eSupplementary 3\u003c/u\u003e\u003c/strong\u003e.\u003c/p\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eOur study is the first meta-analysis to reveal the effects of exercise timing on various health outcomes. The results of this study demonstrated that there was no statistical significance on the effects of exercise timing on individuals\u0026rsquo; health outcomes including anthropometric outcomes, metabolic markers, and sleep parameters.\u003c/p\u003e \u003cp\u003eWhile our meta-analysis found no statistically significant difference in BW, BMI, BFM, and BFFM between the morning and evening exercise groups, some previous studies have reported conflicting outcomes. For the studies supporting morning exercise, Alizadeh et al. [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] found greater reductions in BW (MD: -1.55 vs -0.6 kg; p\u0026thinsp;=\u0026thinsp;0.04), BMI, and BFM in the morning exercise group compared to the evening exercise group after a 6-week supervised aerobic exercise program. Exercising in the morning may result in a stronger metabolic response due to time-dependent molecular signaling, leading to higher utilization of carbohydrates and fat degradation. [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e] This could explain why some studies have shown more significant weight loss in individuals who exercise in the morning.\u003c/p\u003e \u003cp\u003eIn contrast, Mancilla et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] found a greater reduction of fat mass in the evening exercise group (MD: -1.2 vs -0.2 kg; p\u0026thinsp;=\u0026thinsp;0.03) after 12 weeks of tightly controlled progressive exercise. Additionally, Di Blasio et al. [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e] showed a greater reduction of BFM in the evening exercise group than the morning exercise group (MD: -1.71 vs -0.24 kg; p\u0026thinsp;=\u0026thinsp;0.037) after a 3-month partially supervised walking intervention. This favorable effect of evening exercise is supported by a growing body of evidence. The higher levels of interleukin-6 (IL-6), growth hormone, and blood catecholamines during evening exercise lead to greater lipolysis. [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e] These may suggest evening exercise has more effective in health outcomes which can reduce body weight and BMI.\u003c/p\u003e \u003cp\u003eFrom the conflicting results, it might be implied that there may be differences in metabolic responses in individuals depending on the timing of exercise and lifestyles and further research on the effect of exercise timing on various metabolic responses is needed to fully elucidate this effect.\u003c/p\u003e \u003cp\u003eOur findings align with those of a 12-week self-paced aerobic exercise intervention conducted by Brooker et al. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], which involved 250 minutes of exercise per week and showed no significant difference in lipid levels between morning and evening exercise groups. Nevertheless, several studies have indicated that evening exercise may result in more substantial reductions in LDL levels and triglyceride levels compared to morning exercise [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. These differences may be due to the diurnal variation in cholesterol and triglyceride biosynthesis, which is typically higher during the night. As such, it can be hypothesized that evening exercise might exert a more pronounced influence on lipid metabolism, paralleling the effects of statins [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. On the contrary, based on available studies, the relationship between timing of exercise and metabolic markers remains unclear.\u003c/p\u003e \u003cp\u003eIn terms of energy balance, our study resonates with previous research by Ellis et al. [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] and Creasy et al. [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], which found no significant alterations in TDEE or EI between morning and evening exercise groups. However, both studies observed a trend toward an increase in TDEE and EI in the morning exercise group, aligning with the exercise prescription. This suggests that our bodies respond more positively and exhibit diminished responses to evening exercise. One possible mechanism is that morning exercise induces phase advance in individuals with circadian misalignment and promotes the light-dark cycle. [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e] However, it is important to note that both studies had small sample sizes, and the study by Creasy et al. [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] was a pilot study which has no control group, making it difficult to determine if the changes observed were due to the exercise intervention or other factors.\u003c/p\u003e \u003cp\u003eOur study found no statistically significant differences in sleep latency, sleep efficacy, and WASO between individuals who exercised in the morning versus those who exercised in the evening. These results are consistent with several recent studies [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] that also found no significant differences in sleep outcomes between the two exercise timing groups. Notably, a study by Soel et al. [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] reported improvements in sleep latency in both the morning and evening exercise groups, while Teo et al. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] found improvements in sleep quality after exercise in both groups. It's important to recognize that the effects of exercise timing on the sleep-wake cycle can differ depending on an individual's chronotype, post-exercise duration before bedtime, and exercise environment. Morning exercise may delay sleep onset in those with an earlier chronotype, while evening exercise may advance sleep onset. [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e] For individuals with a late chronotype, both morning and evening exercise may advance sleep, potentially due to changes in melatonin secretion. Thus, personalized exercise prescriptions that consider an individual's chronotype and other sleep-related factors may be beneficial in improving sleep outcomes through exercise. [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eThere are several limitations to this study. First, some of the included studies are observational studies in which residual biases are inevitable. Further, a causal relationship between health outcomes and exercise at different timings cannot be established but rather considered as hypothesis generating. Second, significant heterogeneity was observed in our analyses. Several reasons may account for disparities in study design, methods of exercise, definitions of the timing of exercise, and follow-up times. However, only exercise with at least moderate intensity was included per our inclusion criteria to improve study homogenization. Moreover, we used a random effects model in our analysis. Lastly, the included studies in this analysis contain relatively small sample sizes, potentially underpowering to detect differences between the two groups. However, this research at minimum provides the most updated insights on our current understanding of the impacts of timing on exercise in a tangible manner. Future studies could focus on the long-term effects and sustainability of the intervention. While this study examined short-term outcomes, it is essential to understand whether the positive effects persist over an extended period. Longitudinal studies can help determine whether the improvements in physical well-being are maintained over time or if there is a need for ongoing support and reinforcement. Understanding the long-term implications of the intervention is vital for designing effective interventions that lead to lasting changes in individuals' physical well-being.\u003c/p\u003e \u003cp\u003eIn conclusion, our study suggests that there is no significant difference between the outcomes of morning and evening exercise, but there is a significant difference in anthropometric outcomes pre- and post-exercise. Therefore, the timing of exercise may not be as important as the act of exercising itself. Regular exercise, regardless of the time of day, can positively change body composition and overall health. It is important to note that individual preferences and schedules may play a role in determining the optimal time for exercise. Further research is necessary to elucidate the underlying mechanisms by which exercise timing influences diverse health outcomes. Additionally, conducting large-scale randomized controlled trials could be beneficial in detecting any significant differences between the two groups.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eAM: Ante Meridiem (Before Midday)\u003c/p\u003e\n\u003cp\u003eBF: percentage of Body Fat\u003c/p\u003e\n\u003cp\u003eBFM: Body Fat Mass\u003c/p\u003e\n\u003cp\u003eBFFM: Body Fat Free Mass\u003c/p\u003e\n\u003cp\u003eBMI: Body Mass Index\u003c/p\u003e\n\u003cp\u003eBW: Body Weight\u003c/p\u003e\n\u003cp\u003eCI: Confidence Interval\u003c/p\u003e\n\u003cp\u003eEI: Energy Intake\u003c/p\u003e\n\u003cp\u003eHDL: High-Density Lipoprotein\u003c/p\u003e\n\u003cp\u003eIL-6: Interleukin-6\u003c/p\u003e\n\u003cp\u003eLDL: Low-Density Lipoprotein\u003c/p\u003e\n\u003cp\u003eMD: Mean Difference\u003c/p\u003e\n\u003cp\u003eMOOSE: Meta-analysis Of Observational Studies in Epidemiology\u003c/p\u003e\n\u003cp\u003ePM: Post Meridiem (After Midday)\u003c/p\u003e\n\u003cp\u003ePRISMA: Preferred Reporting Items for Systematic reviews and Meta-Analyses\u003c/p\u003e\n\u003cp\u003eSD: Standard Deviation\u003c/p\u003e\n\u003cp\u003eTC: Total Cholesterol\u003c/p\u003e\n\u003cp\u003eTDEE: Total Daily Energy Expenditure\u003c/p\u003e\n\u003cp\u003eTG: Triglycerides\u003c/p\u003e\n\u003cp\u003eWASO: Wake After Sleep Onset\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding: \u003c/strong\u003eNone\u003c/p\u003e\n\u003cp\u003eConflict of interest statement for all authors: We do not have any financial or non-financial potential conflicts of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors’ contributions:\u003c/strong\u003e All authors had access to the data and a role in writing the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and analysed during the current study available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBarger, L. 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Metabolism, 84, 11-27. https://doi.org/10.1016/j.metabol.2017.11.017 \u003c/li\u003e\n\u003cli\u003eSaito, Y., Yoshida, S., Nakaya, N., Hata, Y., \u0026amp; Goto, Y. (1991). Comparison between morning and evening doses of simvastatin in hyperlipidemic subjects. A double-blind comparative study. Arterioscler Thromb, 11(4), 816-826. https://doi.org/10.1161/01.atv.11.4.816 \u003c/li\u003e\n\u003cli\u003eThomas, J. M., Kern, P. A., Bush, H. M., McQuerry, K. J., Black, W. S., Clasey, J. L., \u0026amp; Pendergast, J. S. (2020). Circadian rhythm phase shifts caused by timed exercise vary with chronotype. JCI Insight, 5(3). https://doi.org/10.1172/jci.insight.134270 \u003c/li\u003e\n\u003cli\u003eVitale, J. A., \u0026amp; Weydahl, A. (2017). Chronotype, Physical Activity, and Sport Performance: A Systematic Review. Sports Med, 47(9), 1859-1868. https://doi.org/10.1007/s40279-017-0741-z \u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 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":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"exercise, morning, evening, anthropometric indices, sleep, metabolic markers","lastPublishedDoi":"10.21203/rs.3.rs-4583679/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4583679/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground:\u003c/strong\u003e The relationships between exercise timing and health outcomes including anthropometric indices, metabolic markers, and sleep health have not been clearly established. To gain better insights, we performed the meta-analysis to determine the effects of morning versus evening exercise on various health outcomes.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods: \u003c/strong\u003eWe collected studies from MEDLINE, EMBASE, and Cochrane databases from inception to March 2023 to perform a meta-analysis. Exercise is defined as performing activity at least moderate intensity. For the outcomes of interest, the mean differences (MD) were employed using a random-effects model, the generic inverse variance method of DerSimonian and Laird.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults: \u003c/strong\u003eA total of 716 patients were analyzed from 14 studies including randomized controlled trial and observational studies. We found no significant associations between exercise timing and several health-related parameters. Specifically, the data showed no notable differences in body weight (MD: -0.12 kg [95% CI −0.81 to 0.58]) and BMI (MD: -0.07 kg/m2 [95% CI −0.46 to 0.32]) when comparing morning and evening exercise sessions. Similarly, sleep latency was not significantly affected by exercise timing (MD: -2.24 minutes [95% CI −5.83 to 1.35]). Furthermore, changes in metabolic biomarkers, including LDL (MD: -6.64 mg/dL [95% CI −20.08 to 6.79]) and HDL (MD: 0.09 mg/dL [95% CI 0 to 0.17]), were not significantly associated with the timing of exercise.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion:\u003c/strong\u003e This meta-analysis found no significant relationship between exercise timing and health outcomes including anthropometric indices, metabolic markers, and sleep health. While considered as hypothesis generating, timing of exercise should equally prune patients’ health outcomes.\u003c/p\u003e","manuscriptTitle":"Evening Exercise Does Not Affect Sleep Health: A Systematic Review and Meta-Analysis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-10 11:46:00","doi":"10.21203/rs.3.rs-4583679/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"3be3b8d6-7a1b-4566-b93c-d54eadca4a7d","owner":[],"postedDate":"August 10th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":35462523,"name":"Health sciences/Cardiology"},{"id":35462524,"name":"Health sciences/Medical research"}],"tags":[],"updatedAt":"2024-08-21T07:03:31+00:00","versionOfRecord":[],"versionCreatedAt":"2024-08-10 11:46:00","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4583679","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4583679","identity":"rs-4583679","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}