Body Composition Changes After Bariatric Surgery: Magnitude, Timing, and Determinants of Excessive Fat-Free Mass Loss
Background: Bariatric surgery effectively treats severe obesity, but postoperative weight loss includes reductions in both fat mass (FM) and fat-free mass (FFM). Excessive FFM loss may increase the risk of sarcopenia, frailty, and long-term weight regain, yet its magnitude and determinants are not f...
| Autores: | , , , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2026 |
| País: | España |
| Institución: | Institut d'Investigació i Innovació Parc Taulí (I3PT) |
| Repositorio: | r-I3PT. Repositorio Institucional Producción Científica del Institut d'Investigació i Innovació Parc Taulí |
| OAI Identifier: | oai:i3pt.fundanetsuite.com:p6920 |
| Acceso en línea: | https://i3pt.portalinvestigacion.com/publicaciones/6920 https://www.scopus.com/inward/record.uri?eid=2-s2.0-105028652071&doi=10.3390%2Fjcm15020630&partnerID=40&md5=eefd9bd0688475f7bf4e7fb71a876076 |
| Access Level: | acceso abierto |
| Palabra clave: | bariatric surgery body composition fat-free mass loss sarcopenic obesity weight loss outcomes bioelectrical impedance analysis postoperative monitoring |
| Sumario: | Background: Bariatric surgery effectively treats severe obesity, but postoperative weight loss includes reductions in both fat mass (FM) and fat-free mass (FFM). Excessive FFM loss may increase the risk of sarcopenia, frailty, and long-term weight regain, yet its magnitude and determinants are not fully established. Methods: We conducted a retrospective analysis of a prospectively collected cohort of 179 patients who underwent laparoscopic or robotic Roux-en-Y gastric bypass between January 2020 and December 2022. Anthropometric parameters and body composition (bioelectrical impedance analysis) were measured preoperatively and at 6 and 12 months. The proportion of FFM loss relative to total weight loss (%FFML/WL) was calculated, and excessive FFM loss was defined using published cut-offs (>= 25%, >= 30%, and >= 35%). Predictors of FFM preservation were assessed through stepwise regression. Results: Baseline BMI was 44.1 +/- 4.6 kg/m(2), FM 54.6 +/- 10.7 kg, and FFM 61.1 +/- 11.9 kg. At 6 and 12 months, BMI decreased to 31.0 +/- 4.2 and 28.8 +/- 4.4 kg/m(2), respectively; FM decreased to 35.6 +/- 11.0 and 22.0 +/- 10.0 kg; and FFM to 54.7 +/- 9.5 and 50.1 +/- 7.0 kg (all p < 0.001). Most FFM loss occurred within the first 6 months (mean - 6.4 kg). Median %FFML/WL was 26.4% at 6 months and 28.7% at 12 months. Excessive FFM loss affected 41-46% of patients (>= 25%), 27-31% (>= 30%), and 14% (>= 35%). In multivariable analysis, FFM at 6 months was the only independent predictor of FFM at 12 months (p < 0.001). Conclusions: Bariatric surgery leads to substantial FM and FFM reductions, with nearly half of patients exceeding established %FFML/WL alert thresholds. Early postoperative body composition monitoring may help identify individuals at higher risk of FFM depletion and guide preventive strategies such as adequate protein intake and resistance training. |
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