Longitudinal Changes and Persistence of Extracellular Water Distribution After Sleeve Gastrectomy

Longitudinal Changes and Persistence of Extracellular Water Distribution After Sleeve Gastrectomy | 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 Research Article Longitudinal Changes and Persistence of Extracellular Water Distribution After Sleeve Gastrectomy Masatoshi Nakagawa, Masaki Yoshimatsu, Yu Ueta, Takahiro Ochiai, and 8 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9262179/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract Background Bioelectrical impedance analysis (BIA) is increasingly used to assess body composition after bariatric surgery. However, longitudinal changes in the extracellular water-to-total body water ratio (ECW/TBW) after laparoscopic sleeve gastrectomy (LSG) and their clinical implications remain poorly understood. This study aimed to characterize perioperative changes in ECW/TBW following LSG and to explore its associations with body composition and clinical parameters. Methods This retrospective single-center study included patients with severe obesity who underwent LSG between 2019 and 2025. Of the 23 patients who underwent surgery during the study period, 16 with complete body composition and laboratory data at all scheduled time points were analyzed. Body composition was assessed preoperatively and at 3, 6, and 12 months postoperatively using multifrequency BIA. Longitudinal changes were evaluated using the Friedman test, and correlations were assessed using Spearman’s rank correlation coefficient. Results The median preoperative body mass index was 46.1 kg/m². Body weight, body mass index, and body fat mass decreased significantly during follow-up (p < 0.001). ECW/TBW increased at 3 months after surgery (median 0.401 vs. 0.390 at baseline) and then decreased slightly at 6 and 12 months (both 0.399), remaining marginally higher than baseline (p < 0.001). Preoperative ECW/TBW correlated positively with body mass index (ρ = 0.566, p = 0.022). At 12 months, ECW/TBW showed a modest inverse correlation with serum albumin (ρ = −0.514, p = 0.042) but was not associated with weight-loss metrics or body composition parameters. A strong positive correlation was observed between preoperative and 12-month ECW/TBW values (ρ = 0.695, p = 0.003). Conclusions ECW/TBW showed a characteristic temporal pattern after LSG, with a transient early postoperative increase followed by partial normalization. Baseline ECW/TBW strongly correlated with postoperative values, suggesting persistence of individual fluid distribution characteristics despite substantial weight loss. sleeve gastrectomy body composition bioelectrical impedance analysis extracellular water obesity Figures Figure 1 Figure 2 Figure 3 Introduction Bariatric and metabolic surgery has become widely adopted worldwide as an effective treatment for severe obesity, leading to substantial weight loss and improvement in obesity-related metabolic comorbidities. ( 1 – 3 ) In addition to changes in body weight, bariatric surgery induces profound alterations in body composition and fluid distribution during the postoperative period. ( 4 ) Severe obesity is associated with chronic low-grade inflammation, impaired lymphatic transport, and microvascular dysfunction, which collectively contribute to expansion of the extracellular fluid compartment. ( 5 – 7 ) As a result, the extracellular water-to-total body water ratio (ECW/TBW) is often elevated in individuals with severe obesity. ECW/TBW has been proposed as a useful indicator of body fluid distribution and has been associated with nutritional status, inflammatory burden, and clinical outcomes in various medical conditions, including critical illness and chronic kidney disease. ( 8 – 10 ) Laparoscopic sleeve gastrectomy (LSG) induces rapid reductions in fat mass and changes in lean body mass, particularly during the first postoperative year. ( 11 , 12 ) These alterations may influence the intracellular and extracellular fluid compartments through mechanisms such as rapid catabolism, transient inflammation, and metabolic adaptation. ( 13 ) However, despite the increasing use of bioelectrical impedance analysis (BIA) in bariatric surgery, longitudinal changes in ECW/TBW after LSG and their clinical implications remain poorly understood. ( 14 – 16 ) The aim of this study was therefore to characterize perioperative changes in ECW/TBW during the first 12 months after LSG and to explore its associations with body composition parameters, weight-loss outcomes, and nutritional and inflammatory markers. Methods Study Design and Patients This retrospective, single-center observational study included patients with severe obesity who underwent LSG at our institution between 2019 and 2025. During this period, 23 patients underwent LSG. Of these, 16 patients with complete body composition and laboratory data available at all scheduled time points were included in the final analysis. The primary outcome was the change in ECW/TBW from baseline to 12 months. Secondary outcomes included correlations between ECW/TBW and body composition, weight-loss parameters, and biochemical markers at 12 months. This study was approved by the Institutional Review Board of XXXX (approval No. R-104-8J) and was conducted in accordance with the principles of the Declaration of Helsinki. The requirement for informed consent was waived because of the retrospective nature of the study. Body Composition Measurements and Laboratory Assessments Body composition was measured at four time points—preoperatively and at 3, 6, and 12 months postoperatively—using a multifrequency BIA device (InBody 770; InBody Co., Seoul, Korea). Recorded parameters included body weight, body mass index (BMI), body fat mass, skeletal muscle mass, and ECW/TBW. Measurements were obtained under standardized conditions with patients in the fasting state. Serum albumin and C-reactive protein (CRP) were measured at the same time points. All laboratory analyses were performed in the hospital’s central laboratory. Statistical Analysis Continuous variables are presented as median and range. Longitudinal changes in clinical parameters were analyzed using the Friedman test. Correlations between ECW/TBW and other variables were evaluated using Spearman’s rank correlation coefficient. All statistical analyses were performed using SPSS version 23 (IBM Corp., Armonk, NY, USA). A p-value < 0.05 was considered statistically significant. Results Patient Characteristics Sixteen patients were included in the study. The median preoperative BMI was 46.1 kg/m². Comorbidities included type 2 diabetes mellitus (50%), hypertension (56%), dyslipidemia (75%), sleep apnea syndrome (69%), and metabolic dysfunction-associated steatotic liver disease (50%). No major perioperative complications were reported (Table 1 ). Table 1 Baseline and Perioperative Characteristics of All Patients Variables *Age(years) 44 (18–62) Sex Male : Female 7 : 9 *Body weight (kg) 122.2 (87–158) *BMI (kg/m 2 ) 46.1 (35.4–54.6) *Body fat mass (kg) 57.4 (40.1–78.7) *Body fat percentage (%) 50.7 (35.2–56.5) *Skeletal muscle mass (kg) 58.7 (40.9–70.4) *ECW/TBW 0.390 (0.379–0.404) *Serum albumin (g/dL) 4.2 (2.9–5.5) *Serum CRP (mg/dL) 0.42 (0.01–4.13) *Serum transthyretin (mg/dL) 23 (8.7–30.2) Hypertension Yes : No 9 : 7 Diabetes mellitus Yes : No 8 : 8 Dyslipidemia Yes : No 12 : 4 Sleep apnea syndrome Yes : No 11 : 5 MASLD Yes : No 8 : 8 *Operative time (min) 191 (140–263) *Blood loss (ml) 1 (1–50) Postoperative complication(C-D ≥ II) 0 *Postoperative hospital stay (days) 9 (7–28) BMI: body mass index; ECW/TBW: extracellular water-to-total body water ratio; CRP: C-reactive protein; MASLD: metabolic dysfunction-associated steatotic liver disease; C-D: Clavien-Dindo classification. *Values are presented as median (range). Longitudinal Changes in Body Composition and ECW/TBW Significant reductions were observed in body weight, BMI, and body fat mass during the follow-up period (p < 0.001). Skeletal muscle mass decreased during the early postoperative period and remained slightly reduced at 12 months. ECW/TBW increased significantly at 3 months after surgery (median 0.401 vs. 0.390 at baseline), followed by a slight decrease at 6 and 12 months (both 0.399). However, the ratio remained slightly higher than the preoperative value throughout the study period (p < 0.001) (Table 2 , Fig. 1 ). Individual trajectories of ECW/TBW are shown in Fig. 2 . Table 2 Longitudinal Changes in Body Composition and Laboratory Markers After Sleeve Gastrectomy Body weight (kg) Pre-op 3 months 6 months 12 months p-value 122.2 (87–158) 103.7 (72.5-135.5) 96.3 (66.0-132) 84.9 (52.2-130.5) < 0.001 BMI (kg/m 2 ) 46.1 (35.4–63.3) 39.1 (28.1–48.5) 35.8 (26.6–48.9) 29.9 (21.1–49.3) < 0.001 %TWL - 17.7 (9.84–23.5) 21.4 (12.9–33.4) 23.0 (9.76–47.3) < 0.001 %EWL - 43.0 (20.6–73.6) 54.4 (25.1–88.0) 59.9 (18.0-128.8) < 0.001 Body fat mass (kg) 57.4 (40.1–78.7) 46.5 (20.3–70.8) 40.3 (13.4–67.3) 35.2 (8.0-68.8) < 0.001 Body fat percentage (%) 50.7 (35.2–56.5) 46.2 (22.1–57.7) 45.4 (15.2–55.2) 44.4 (12.6–55.9) < 0.001 Skeletal muscle mass (kg) 58.7 (40.9–70.4) 53.8 (36.8–68.7) 52.0 (38.1–68.9) 51.9 (37.7–67.0) < 0.001 ECW/TBW 0.390 (0.379–0.404) 0.401 (0.387–0.412) 0.399 (0.378–0.412) 0.399 (0.386–0.418) < 0.001 Serum albumin (g/dL) 4.2 (2.9–5.5) 4.1 (3.1–5.2) 4.0 (3.3–4.9) 4.0 (3.0-4.9) 0.513 Serum CRP (mg/dL) 0.42 (0.01–4.13) 0.22 (0.08–2.35) 0.15 (0.02–1.07) 0.04 (0.01–2.76) 0.036 BMI: body mass index; TWL: total weight loss; EWL: excess weight loss; ECW/TBW: extracellular water-to-total body water ratio; CRP: C-reactive protein. *Values are presented as median (range). Correlation Between Preoperative ECW/TBW and Baseline Characteristics Preoperative ECW/TBW showed a significant positive correlation with BMI (Spearman’s ρ = 0.566, p = 0.022). Positive trends were also observed for body weight (ρ = 0.486, p = 0.056) and body fat mass (ρ = 0.452, p = 0.079), although these did not reach statistical significance. No significant correlations were found with age, serum albumin, CRP, body fat percentage, or skeletal muscle mass (Table 3 ). Table 3 Correlation Between Preoperative ECW/TBW and Baseline Clinical Parameters Variables ρ(Spearman) P value age -0.169 0.532 Body weight 0.486 0.056 BMI 0.566 0.022 Serum albumin -0.174 0.518 Serum CRP -0.092 0.734 Body fat mass 0.452 0.079 Body fat percentage 0.301 0.257 Skeletal muscle mass 0.170 0.529 ECW/TBW: extracellular water-to-total body water ratio; BMI: body mass index; CRP: C-reactive protein. Correlation Between ECW/TBW at 12 Months and Clinical Parameters At 12 months, ECW/TBW showed a significant negative correlation with serum albumin (Spearman’s ρ = −0.514, p = 0.042). No significant associations were observed with body weight, BMI, total weight loss (%TWL), excess weight loss (%EWL), body fat mass, body fat percentage, skeletal muscle mass, or CRP (Table 4 ). Table 4 Correlation Between ECW/TBW at 12 Months and Clinical Parameters Variables ρ(Spearman) P value age 0.013 0.963 Body weight -0.172 0.524 BMI -0.001 0.996 %TWL 0.322 0.223 %EWL 0.228 0.395 Serum albumin -0.514 0.042 Serum CRP 0.013 0.961 Body fat mass -0.078 0.774 Body fat percentage -0.222 0.408 Percent change in fat mass -0.259 0.333 Skeletal muscle mass -0.159 0.557 ECW/TBW: extracellular water-to-total body water ratio; BMI: body mass index; TWL: total body weight loss; EWL: excess weight loss; CRP: C-reactive protein. Association Between Preoperative and 12-Month ECW/TBW A significant positive correlation was observed between preoperative ECW/TBW and ECW/TBW at 12 months (Spearman ρ = 0.695, p = 0.003) (Fig. 3 ). Discussion This study evaluated longitudinal changes in ECW/TBW after LSG using standardized BIA and explored its clinical correlates. Four main findings emerged. First, ECW/TBW increased uniformly at 3 months postoperatively and then declined modestly at 6 and 12 months, although it remained slightly higher than baseline. Second, preoperative ECW/TBW correlated positively with BMI, supporting the concept that severe obesity is associated with expansion of the extracellular fluid compartment. Third, ECW/TBW at 12 months was not associated with the magnitude of weight loss or body composition parameters but showed a modest yet significant inverse correlation with serum albumin. Finally, preoperative ECW/TBW strongly correlated with ECW/TBW at 12 months, indicating that individual fluid distribution characteristics may persist even after substantial weight loss. From a pathophysiological perspective, severe obesity is associated with chronic low-grade inflammation, impaired lymphatic transport, and microvascular dysfunction, which collectively promote interstitial fluid accumulation and expansion of the extracellular fluid compartment. Adipose tissue-derived inflammatory mediators may increase vascular permeability and contribute to extracellular fluid expansion. ( 5 – 7 , 17 ) In our cohort, preoperative ECW/TBW was significantly correlated with BMI and showed positive trends with body weight and body fat mass, but not with skeletal muscle mass, albumin, or CRP, suggesting that ECW/TBW in severe obesity primarily reflects obesity-related alterations in fluid distribution rather than overt malnutrition or systemic inflammation. The universal increase in ECW/TBW observed at 3 months likely reflects early postoperative physiological adaptation during the rapid weight-loss phase. Rapid reductions in lean tissue and intracellular water—particularly in the setting of early catabolic stress—may transiently increase the relative proportion of extracellular water. In addition, transient inflammatory responses and metabolic stress during the early postoperative period may further influence fluid redistribution. Notably, the increase in ECW/TBW at 3 months was observed consistently across nearly all patients, suggesting a common physiological response rather than random individual variation. A notable finding of this study was the strong correlation between preoperative and 12-month ECW/TBW values. Patients with higher baseline ECW/TBW tended to maintain relatively higher values at 1 year, suggesting that fluid distribution may partly represent a patient-specific physiological trait. This observation implies that obesity-associated alterations in extracellular fluid balance may not be fully reversible within the first postoperative year despite substantial weight loss. Interestingly, ECW/TBW at 12 months was not associated with weight-loss magnitude (%TWL or %EWL) or body composition indices such as body fat mass and skeletal muscle mass. These findings indicate that ECW/TBW provides information distinct from that provided by conventional weight-loss metrics. Instead, ECW/TBW showed a modest yet significant inverse correlation with serum albumin at 12 months. Because albumin contributes to plasma oncotic pressure, relatively lower albumin levels may facilitate fluid shifts toward the extracellular compartment. Although the strength of this association was limited, these findings suggest that postoperative ECW/TBW may partly reflect nutritional or protein status even when systemic inflammation, as indicated by CRP, is not prominent. ( 18 ) From a clinical standpoint, ECW/TBW may therefore be more informative for understanding perioperative physiological adaptation and individual fluid regulation than as a marker of weight-loss efficacy. Early postoperative changes in ECW/TBW may reflect transient shifts in body fluid compartments during rapid weight reduction, whereas longer-term values may be influenced by baseline patient characteristics. Monitoring ECW/TBW could therefore provide additional insight into postoperative fluid dynamics and metabolic adaptation in patients undergoing bariatric surgery. Several limitations should be acknowledged. First, this was a retrospective study conducted at a single institution with a relatively small sample size, which may limit statistical power and generalizability. Second, ECW/TBW was measured using BIA rather than reference dilution techniques, although BIA is widely used for longitudinal body composition assessment in routine clinical practice. Finally, the follow-up period was limited to 12 months, and longer-term studies are needed to determine whether ECW/TBW eventually normalizes after prolonged weight stabilization. In conclusion, ECW/TBW showed a distinct temporal pattern following LSG, characterized by a uniform early postoperative increase followed by partial normalization. Preoperative ECW/TBW strongly correlated with postoperative values, suggesting persistence of individual fluid distribution characteristics despite substantial weight loss. ECW/TBW therefore appears to reflect obesity-related extracellular fluid expansion and postoperative physiological adaptation rather than simply the magnitude of weight reduction. Declarations Funding: None Conflict of Interest: The authors declare no conflicts of interest. Author Contribution All authors contributed to the study concept and design, data acquisition, interpretation, and final approval of the manuscript. 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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-9262179","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":617785869,"identity":"566958c5-a96a-4761-9e4a-12654135e684","order_by":0,"name":"Masatoshi 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laparoscopic sleeve gastrectomy.\u003cbr\u003e\nBox plots represent the median and interquartile range, and dots indicate individual patients. ECW/TBW increased at 3 months postoperatively and remained slightly elevated at 6 and 12 months compared with baseline.\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-9262179/v1/29d6d1a5975253a26fd0aa49.png"},{"id":106726644,"identity":"aba10f7a-643f-4b5e-a777-10ae315d1c56","added_by":"auto","created_at":"2026-04-12 18:36:57","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":570328,"visible":true,"origin":"","legend":"\u003cp\u003eIndividual trajectories of ECW/TBW following laparoscopic sleeve gastrectomy. Each gray line represents an individual patient. The black line indicates the median ECW/TBW value at each time point.\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-9262179/v1/6c9375d0622ce6eb8498b017.png"},{"id":106726468,"identity":"8dc22ef2-3644-46a7-bf50-c8f3ae3e5f16","added_by":"auto","created_at":"2026-04-12 18:36:14","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":296353,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation between preoperative ECW/TBW and ECW/TBW at 12 months after laparoscopic sleeve gastrectomy. Each dot represents an individual patient. A significant positive correlation was observed between baseline and 12-month ECW/TBW values (Spearman’s ρ = 0.695, p = 0.003).\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-9262179/v1/cdee969b871fa30486954df9.png"},{"id":106727806,"identity":"8052aba7-b783-4f8b-9894-19bf5241754c","added_by":"auto","created_at":"2026-04-12 18:40:56","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1946617,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9262179/v1/d142ba9b-d1b7-4ad5-b7ad-de97c289e7ff.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Longitudinal Changes and Persistence of Extracellular Water Distribution After Sleeve Gastrectomy","fulltext":[{"header":"Introduction","content":"\u003cp\u003eBariatric and metabolic surgery has become widely adopted worldwide as an effective treatment for severe obesity, leading to substantial weight loss and improvement in obesity-related metabolic comorbidities. (\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e–\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e) In addition to changes in body weight, bariatric surgery induces profound alterations in body composition and fluid distribution during the postoperative period. (\u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eSevere obesity is associated with chronic low-grade inflammation, impaired lymphatic transport, and microvascular dysfunction, which collectively contribute to expansion of the extracellular fluid compartment. (\u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e–\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e) As a result, the extracellular water-to-total body water ratio (ECW/TBW) is often elevated in individuals with severe obesity. ECW/TBW has been proposed as a useful indicator of body fluid distribution and has been associated with nutritional status, inflammatory burden, and clinical outcomes in various medical conditions, including critical illness and chronic kidney disease. (\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e–\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eLaparoscopic sleeve gastrectomy (LSG) induces rapid reductions in fat mass and changes in lean body mass, particularly during the first postoperative year. (\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e) These alterations may influence the intracellular and extracellular fluid compartments through mechanisms such as rapid catabolism, transient inflammation, and metabolic adaptation. (\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e) However, despite the increasing use of bioelectrical impedance analysis (BIA) in bariatric surgery, longitudinal changes in ECW/TBW after LSG and their clinical implications remain poorly understood. (\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e–\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eThe aim of this study was therefore to characterize perioperative changes in ECW/TBW during the first 12 months after LSG and to explore its associations with body composition parameters, weight-loss outcomes, and nutritional and inflammatory markers.\u003c/p\u003e "},{"header":"Methods","content":"\u003cp\u003eStudy Design and Patients\u003c/p\u003e\u003cp\u003eThis retrospective, single-center observational study included patients with severe obesity who underwent LSG at our institution between 2019 and 2025. During this period, 23 patients underwent LSG. Of these, 16 patients with complete body composition and laboratory data available at all scheduled time points were included in the final analysis. The primary outcome was the change in ECW/TBW from baseline to 12 months. Secondary outcomes included correlations between ECW/TBW and body composition, weight-loss parameters, and biochemical markers at 12 months. This study was approved by the Institutional Review Board of XXXX (approval No. R-104-8J) and was conducted in accordance with the principles of the Declaration of Helsinki. The requirement for informed consent was waived because of the retrospective nature of the study.\u003c/p\u003e\n\u003ch3\u003eBody Composition Measurements and Laboratory Assessments\u003c/h3\u003e\n\u003cp\u003eBody composition was measured at four time points\u0026mdash;preoperatively and at 3, 6, and 12 months postoperatively\u0026mdash;using a multifrequency BIA device (InBody 770; InBody Co., Seoul, Korea). Recorded parameters included body weight, body mass index (BMI), body fat mass, skeletal muscle mass, and ECW/TBW. Measurements were obtained under standardized conditions with patients in the fasting state. Serum albumin and C-reactive protein (CRP) were measured at the same time points. All laboratory analyses were performed in the hospital\u0026rsquo;s central laboratory.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eContinuous variables are presented as median and range. Longitudinal changes in clinical parameters were analyzed using the Friedman test. Correlations between ECW/TBW and other variables were evaluated using Spearman\u0026rsquo;s rank correlation coefficient. All statistical analyses were performed using SPSS version 23 (IBM Corp., Armonk, NY, USA). A p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003ePatient Characteristics\u003c/h2\u003e \u003cp\u003eSixteen patients were included in the study. The median preoperative BMI was 46.1 kg/m\u0026sup2;. Comorbidities included type 2 diabetes mellitus (50%), hypertension (56%), dyslipidemia (75%), sleep apnea syndrome (69%), and metabolic dysfunction-associated steatotic liver disease (50%). No major perioperative complications were reported (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eBaseline and Perioperative Characteristics of All Patients\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e*Age(years)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e44 (18\u0026ndash;62)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMale : Female\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7 : 9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e*Body weight (kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e122.2 (87\u0026ndash;158)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e*BMI (kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e46.1 (35.4\u0026ndash;54.6)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e*Body fat mass (kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e57.4 (40.1\u0026ndash;78.7)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e*Body fat percentage (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50.7 (35.2\u0026ndash;56.5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e*Skeletal muscle mass (kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e58.7 (40.9\u0026ndash;70.4)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e*ECW/TBW\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.390 (0.379\u0026ndash;0.404)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e*Serum albumin (g/dL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.2 (2.9\u0026ndash;5.5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e*Serum CRP (mg/dL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.42 (0.01\u0026ndash;4.13)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e*Serum transthyretin (mg/dL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e23 (8.7\u0026ndash;30.2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHypertension\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYes : No\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9 : 7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDiabetes mellitus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYes : No\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8 : 8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDyslipidemia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYes : No\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12 : 4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSleep apnea syndrome\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYes : No\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11 : 5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMASLD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYes : No\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8 : 8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e*Operative time (min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e191 (140\u0026ndash;263)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e*Blood loss (ml)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (1\u0026ndash;50)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative complication(C-D\u0026thinsp;\u0026ge;\u0026thinsp;II)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e*Postoperative hospital stay (days)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9 (7\u0026ndash;28)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"3\"\u003eBMI: body mass index; ECW/TBW: extracellular water-to-total body water ratio; CRP: C-reactive protein; MASLD: metabolic dysfunction-associated steatotic liver disease; C-D: Clavien-Dindo classification.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"3\"\u003e*Values are presented as median (range).\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eLongitudinal Changes in Body Composition and ECW/TBW\u003c/h3\u003e\n\u003cp\u003eSignificant reductions were observed in body weight, BMI, and body fat mass during the follow-up period (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Skeletal muscle mass decreased during the early postoperative period and remained slightly reduced at 12 months. ECW/TBW increased significantly at 3 months after surgery (median 0.401 vs. 0.390 at baseline), followed by a slight decrease at 6 and 12 months (both 0.399). However, the ratio remained slightly higher than the preoperative value throughout the study period (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Individual trajectories of ECW/TBW are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eLongitudinal Changes in Body Composition and Laboratory Markers After Sleeve Gastrectomy\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eBody weight (kg)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePre-op\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3 months\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6 months\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e12 months\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e122.2 (87\u0026ndash;158)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e103.7 (72.5-135.5)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e96.3 (66.0-132)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e84.9 (52.2-130.5)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI (kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e46.1 (35.4\u0026ndash;63.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e39.1 (28.1\u0026ndash;48.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e35.8 (26.6\u0026ndash;48.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e29.9 (21.1\u0026ndash;49.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e%TWL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e17.7 (9.84\u0026ndash;23.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e21.4 (12.9\u0026ndash;33.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e23.0 (9.76\u0026ndash;47.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e%EWL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e43.0 (20.6\u0026ndash;73.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e54.4 (25.1\u0026ndash;88.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e59.9 (18.0-128.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBody fat mass (kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e57.4 (40.1\u0026ndash;78.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e46.5 (20.3\u0026ndash;70.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e40.3 (13.4\u0026ndash;67.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e35.2 (8.0-68.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBody fat percentage (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e50.7 (35.2\u0026ndash;56.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e46.2 (22.1\u0026ndash;57.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e45.4 (15.2\u0026ndash;55.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e44.4 (12.6\u0026ndash;55.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSkeletal muscle mass (kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e58.7 (40.9\u0026ndash;70.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e53.8 (36.8\u0026ndash;68.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e52.0 (38.1\u0026ndash;68.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e51.9 (37.7\u0026ndash;67.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eECW/TBW\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.390 (0.379\u0026ndash;0.404)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.401 (0.387\u0026ndash;0.412)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.399 (0.378\u0026ndash;0.412)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.399 (0.386\u0026ndash;0.418)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerum albumin (g/dL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.2 (2.9\u0026ndash;5.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4.1 (3.1\u0026ndash;5.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.0 (3.3\u0026ndash;4.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e4.0 (3.0-4.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.513\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerum CRP (mg/dL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.42 (0.01\u0026ndash;4.13)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.22 (0.08\u0026ndash;2.35)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.15 (0.02\u0026ndash;1.07)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.04 (0.01\u0026ndash;2.76)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.036\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"6\"\u003eBMI: body mass index; TWL: total weight loss; EWL: excess weight loss; ECW/TBW: extracellular water-to-total body water ratio; CRP: C-reactive protein.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"6\"\u003e*Values are presented as median (range).\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eCorrelation Between Preoperative ECW/TBW and Baseline Characteristics\u003c/h3\u003e\n\u003cp\u003ePreoperative ECW/TBW showed a significant positive correlation with BMI (Spearman\u0026rsquo;s ρ\u0026thinsp;=\u0026thinsp;0.566, p\u0026thinsp;=\u0026thinsp;0.022). Positive trends were also observed for body weight (ρ\u0026thinsp;=\u0026thinsp;0.486, p\u0026thinsp;=\u0026thinsp;0.056) and body fat mass (ρ\u0026thinsp;=\u0026thinsp;0.452, p\u0026thinsp;=\u0026thinsp;0.079), although these did not reach statistical significance. No significant correlations were found with age, serum albumin, CRP, body fat percentage, or skeletal muscle mass (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCorrelation Between Preoperative ECW/TBW and Baseline Clinical Parameters\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eρ(Spearman)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eage\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.169\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.532\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBody weight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.486\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.056\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.566\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.022\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerum albumin\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.174\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.518\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerum CRP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.092\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.734\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBody fat mass\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.452\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.079\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBody fat percentage\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.301\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.257\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSkeletal muscle mass\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.170\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.529\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"3\"\u003eECW/TBW: extracellular water-to-total body water ratio; BMI: body mass index; CRP: C-reactive protein.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eCorrelation Between ECW/TBW at 12 Months and Clinical Parameters\u003c/h2\u003e \u003cp\u003eAt 12 months, ECW/TBW showed a significant negative correlation with serum albumin (Spearman\u0026rsquo;s ρ = \u0026minus;0.514, p\u0026thinsp;=\u0026thinsp;0.042). No significant associations were observed with body weight, BMI, total weight loss (%TWL), excess weight loss (%EWL), body fat mass, body fat percentage, skeletal muscle mass, or CRP (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCorrelation Between ECW/TBW at 12 Months and Clinical Parameters\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eρ(Spearman)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eage\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.963\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBody weight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.172\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.524\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.996\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e%TWL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.322\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.223\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e%EWL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.228\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.395\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerum albumin\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.514\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.042\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerum CRP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.961\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBody fat mass\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.078\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.774\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBody fat percentage\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.222\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.408\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePercent change in fat mass\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.259\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.333\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSkeletal muscle mass\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.159\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.557\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"3\"\u003eECW/TBW: extracellular water-to-total body water ratio; BMI: body mass index; TWL: total body weight loss; EWL: excess weight loss; CRP: C-reactive protein.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eAssociation Between Preoperative and 12-Month ECW/TBW\u003c/h3\u003e\n\u003cp\u003eA significant positive correlation was observed between preoperative ECW/TBW and ECW/TBW at 12 months (Spearman ρ\u0026thinsp;=\u0026thinsp;0.695, p\u0026thinsp;=\u0026thinsp;0.003) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study evaluated longitudinal changes in ECW/TBW after LSG using standardized BIA and explored its clinical correlates. Four main findings emerged. First, ECW/TBW increased uniformly at 3 months postoperatively and then declined modestly at 6 and 12 months, although it remained slightly higher than baseline. Second, preoperative ECW/TBW correlated positively with BMI, supporting the concept that severe obesity is associated with expansion of the extracellular fluid compartment. Third, ECW/TBW at 12 months was not associated with the magnitude of weight loss or body composition parameters but showed a modest yet significant inverse correlation with serum albumin. Finally, preoperative ECW/TBW strongly correlated with ECW/TBW at 12 months, indicating that individual fluid distribution characteristics may persist even after substantial weight loss.\u003c/p\u003e \u003cp\u003eFrom a pathophysiological perspective, severe obesity is associated with chronic low-grade inflammation, impaired lymphatic transport, and microvascular dysfunction, which collectively promote interstitial fluid accumulation and expansion of the extracellular fluid compartment. Adipose tissue-derived inflammatory mediators may increase vascular permeability and contribute to extracellular fluid expansion. (\u003cspan additionalcitationids=\"CR6\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e) In our cohort, preoperative ECW/TBW was significantly correlated with BMI and showed positive trends with body weight and body fat mass, but not with skeletal muscle mass, albumin, or CRP, suggesting that ECW/TBW in severe obesity primarily reflects obesity-related alterations in fluid distribution rather than overt malnutrition or systemic inflammation.\u003c/p\u003e \u003cp\u003eThe universal increase in ECW/TBW observed at 3 months likely reflects early postoperative physiological adaptation during the rapid weight-loss phase. Rapid reductions in lean tissue and intracellular water\u0026mdash;particularly in the setting of early catabolic stress\u0026mdash;may transiently increase the relative proportion of extracellular water. In addition, transient inflammatory responses and metabolic stress during the early postoperative period may further influence fluid redistribution. Notably, the increase in ECW/TBW at 3 months was observed consistently across nearly all patients, suggesting a common physiological response rather than random individual variation.\u003c/p\u003e \u003cp\u003eA notable finding of this study was the strong correlation between preoperative and 12-month ECW/TBW values. Patients with higher baseline ECW/TBW tended to maintain relatively higher values at 1 year, suggesting that fluid distribution may partly represent a patient-specific physiological trait. This observation implies that obesity-associated alterations in extracellular fluid balance may not be fully reversible within the first postoperative year despite substantial weight loss.\u003c/p\u003e \u003cp\u003eInterestingly, ECW/TBW at 12 months was not associated with weight-loss magnitude (%TWL or %EWL) or body composition indices such as body fat mass and skeletal muscle mass. These findings indicate that ECW/TBW provides information distinct from that provided by conventional weight-loss metrics. Instead, ECW/TBW showed a modest yet significant inverse correlation with serum albumin at 12 months. Because albumin contributes to plasma oncotic pressure, relatively lower albumin levels may facilitate fluid shifts toward the extracellular compartment. Although the strength of this association was limited, these findings suggest that postoperative ECW/TBW may partly reflect nutritional or protein status even when systemic inflammation, as indicated by CRP, is not prominent. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eFrom a clinical standpoint, ECW/TBW may therefore be more informative for understanding perioperative physiological adaptation and individual fluid regulation than as a marker of weight-loss efficacy. Early postoperative changes in ECW/TBW may reflect transient shifts in body fluid compartments during rapid weight reduction, whereas longer-term values may be influenced by baseline patient characteristics. Monitoring ECW/TBW could therefore provide additional insight into postoperative fluid dynamics and metabolic adaptation in patients undergoing bariatric surgery.\u003c/p\u003e \u003cp\u003eSeveral limitations should be acknowledged. First, this was a retrospective study conducted at a single institution with a relatively small sample size, which may limit statistical power and generalizability. Second, ECW/TBW was measured using BIA rather than reference dilution techniques, although BIA is widely used for longitudinal body composition assessment in routine clinical practice. Finally, the follow-up period was limited to 12 months, and longer-term studies are needed to determine whether ECW/TBW eventually normalizes after prolonged weight stabilization.\u003c/p\u003e \u003cp\u003eIn conclusion, ECW/TBW showed a distinct temporal pattern following LSG, characterized by a uniform early postoperative increase followed by partial normalization. Preoperative ECW/TBW strongly correlated with postoperative values, suggesting persistence of individual fluid distribution characteristics despite substantial weight loss. ECW/TBW therefore appears to reflect obesity-related extracellular fluid expansion and postoperative physiological adaptation rather than simply the magnitude of weight reduction.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eFunding:\u003c/h2\u003e \u003cp\u003eNone\u003c/p\u003e \u003cp\u003eConflict of Interest: The authors declare no conflicts of interest.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAll authors contributed to the study concept and design, data acquisition, interpretation, and final approval of the manuscript. MN contributed to data analysis and drafting of the article.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eCourcoulas AP, Daigle CR, Arterburn DE. Long term outcomes of metabolic/bariatric surgery in adults. BMJ. 2023;383:e071027.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAngrisani L, Santonicola A, Iovino P, Palma R, Kow L, Prager G, et al. IFSO Worldwide Survey 2020\u0026ndash;2021: Current Trends for Bariatric and Metabolic Procedures. Obes Surg. 2024;34(4):1075\u0026ndash;85.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMingrone G, Panunzi S, De Gaetano A, Guidone C, Iaconelli A, Capristo E, et al. Metabolic surgery versus conventional medical therapy in patients with type 2 diabetes: 10-year follow-up of an open-label, single-centre, randomised controlled trial. Lancet. 2021;397(10271):293\u0026ndash;304.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHarper ME, Dent RRM, McPherson R. High-Quality Weight Loss in Obesity: Importance of Skeletal Muscle. Diabetes. 2025;74(12):2191\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWeitman ES, Aschen SZ, Farias-Eisner G, Albano N, Cuzzone DA, Ghanta S, et al. Obesity impairs lymphatic fluid transport and dendritic cell migration to lymph nodes. PLoS ONE. 2013;8(8):e70703.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKhanna D, Khanna S, Khanna P, Kahar P, Patel BM. Obesity: A Chronic Low-Grade Inflammation and Its Markers. Cureus. 2022;14(2):e22711.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGregor MF, Hotamisligil GS. Inflammatory mechanisms in obesity. Annu Rev Immunol. 2011;29:415\u0026ndash;45.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLee Y, Kwon O, Shin CS, Lee SM. Use of bioelectrical impedance analysis for the assessment of nutritional status in critically ill patients. Clin Nutr Res. 2015;4(1):32\u0026ndash;40.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang Y, Liu J, Hao H, Lu Q, Zhang L, Wei G, et al. Non-linear association between extracellular water/total body water ratio and all-cause mortality: a population-based cohort study. Sci Rep. 2025;15(1):19032.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYajima T, Yajima K. Association of extracellular water/total body water ratio with protein-energy wasting and mortality in patients on hemodialysis. Sci Rep. 2023;13(1):14257.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTalalaj M, Bogolowska-Stieblich A, Wasowski M, Binda A, Jaworski P, Wrzosek M, et al. The Influence of Laparoscopic Sleeve Gastrectomy on Body Composition and Fat Distribution in Obese Caucasian Men and Women. Obes Surg. 2020;30(10):3974\u0026ndash;81.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNakaguchi H, Matsuura B, Miyake T, Senba H, Furukawa S, Yoshida M, et al. Body Composition Changes and Factors Influencing the Total Weight Loss Rate After Laparoscopic Sleeve Gastrectomy. Clin Pract. 2024;14(6):2608\u0026ndash;22.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMazariegos M, Kral JG, Wang J, Waki M, Heymsfield SB, Pierson RN Jr., et al. Body composition and surgical treatment of obesity. Effects of weight loss on fluid distribution. Ann Surg. 1992;216(1):69\u0026ndash;73.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBarzin M, Heidari Almasi M, Mahdavi M, Khalaj A, Valizadeh M, Hosseinpanah F. Body Composition Changes Following Sleeve Gastrectomy Vs. One-Anastomosis Gastric Bypass: Tehran Obesity Treatment Study (TOTS). Obes Surg. 2021;31(12):5286\u0026ndash;94.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ede Paris FGC, Padoin AV, Mottin CC, de Paris MF. Assessment of Changes in Body Composition During the First Postoperative Year After Bariatric Surgery. Obes Surg. 2019;29(9):3054\u0026ndash;61.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWiden EM, Strain G, King WC, Yu W, Lin S, Goodpaster B, et al. Validity of bioelectrical impedance analysis for measuring changes in body water and percent fat after bariatric surgery. Obes Surg. 2014;24(6):847\u0026ndash;54.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWeisberg SP, McCann D, Desai M, Rosenbaum M, Leibel RL, Ferrante AW. Jr. Obesity is associated with macrophage accumulation in adipose tissue. J Clin Invest. 2003;112(12):1796\u0026ndash;808.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSoeters PB, Wolfe RR, Shenkin A. Hypoalbuminemia: Pathogenesis and Clinical Significance. JPEN J Parenter Enter Nutr. 2019;43(2):181\u0026ndash;93.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"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":"obesity-surgery","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"obsu","sideBox":"Learn more about [Obesity Surgery](https://link.springer.com/journal/11695)","snPcode":"11695","submissionUrl":"https://submission.springernature.com/new-submission/11695/3","title":"Obesity Surgery","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"sleeve gastrectomy, body composition, bioelectrical impedance analysis, extracellular water, obesity","lastPublishedDoi":"10.21203/rs.3.rs-9262179/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9262179/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eBioelectrical impedance analysis (BIA) is increasingly used to assess body composition after bariatric surgery. However, longitudinal changes in the extracellular water-to-total body water ratio (ECW/TBW) after laparoscopic sleeve gastrectomy (LSG) and their clinical implications remain poorly understood. This study aimed to characterize perioperative changes in ECW/TBW following LSG and to explore its associations with body composition and clinical parameters.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThis retrospective single-center study included patients with severe obesity who underwent LSG between 2019 and 2025. Of the 23 patients who underwent surgery during the study period, 16 with complete body composition and laboratory data at all scheduled time points were analyzed. Body composition was assessed preoperatively and at 3, 6, and 12 months postoperatively using multifrequency BIA. Longitudinal changes were evaluated using the Friedman test, and correlations were assessed using Spearman\u0026rsquo;s rank correlation coefficient.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThe median preoperative body mass index was 46.1 kg/m\u0026sup2;. Body weight, body mass index, and body fat mass decreased significantly during follow-up (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). ECW/TBW increased at 3 months after surgery (median 0.401 vs. 0.390 at baseline) and then decreased slightly at 6 and 12 months (both 0.399), remaining marginally higher than baseline (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Preoperative ECW/TBW correlated positively with body mass index (ρ\u0026thinsp;=\u0026thinsp;0.566, p\u0026thinsp;=\u0026thinsp;0.022). At 12 months, ECW/TBW showed a modest inverse correlation with serum albumin (ρ = \u0026minus;0.514, p\u0026thinsp;=\u0026thinsp;0.042) but was not associated with weight-loss metrics or body composition parameters. A strong positive correlation was observed between preoperative and 12-month ECW/TBW values (ρ\u0026thinsp;=\u0026thinsp;0.695, p\u0026thinsp;=\u0026thinsp;0.003).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eECW/TBW showed a characteristic temporal pattern after LSG, with a transient early postoperative increase followed by partial normalization. Baseline ECW/TBW strongly correlated with postoperative values, suggesting persistence of individual fluid distribution characteristics despite substantial weight loss.\u003c/p\u003e","manuscriptTitle":"Longitudinal Changes and Persistence of Extracellular Water Distribution After Sleeve Gastrectomy","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-10 07:26:35","doi":"10.21203/rs.3.rs-9262179/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewersInvited","content":"","date":"2026-04-05T09:17:03+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-02T15:08:10+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-04-01T13:20:14+00:00","index":"","fulltext":""},{"type":"submitted","content":"Obesity Surgery","date":"2026-03-30T03:47:18+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"obesity-surgery","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"obsu","sideBox":"Learn more about [Obesity Surgery](https://link.springer.com/journal/11695)","snPcode":"11695","submissionUrl":"https://submission.springernature.com/new-submission/11695/3","title":"Obesity Surgery","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"2aa274d1-7ae9-42a4-84d5-04c7e86dc3d3","owner":[],"postedDate":"April 10th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-10T07:26:35+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-10 07:26:35","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9262179","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9262179","identity":"rs-9262179","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}