Abstract
BACKGROUND: Metabolic bariatric surgery (MBS) effectively reduces fat mass (FM), but how to best preserve muscle and bone mass after MBS is unknown. OBJECTIVE: This study aimed to evaluate the effect of aerobic, resistance and combined exercise regimens on body composition, bone mineral density (BMD) and physical function in adults following MBS. METHODS: Patients were randomized into aerobic, resistance, combined and control groups after undergoing MBS. Exercise groups completed a 26-week supervised program (three sessions per week) with progressively increasing intensity. The primary outcome was the change in fat-free mass (FFM) measured by dual-energy X-ray absorptiometry (DXA). Secondary outcomes included FM, hip, femoral neck and lumbar spine BMD, serum collagen type I C-telopeptide (CTX) and physical function (e.g., 6-min walk test and handgrip strength). Between-group differences were assessed using Bayesian analysis of covariance (ANCOVA) adjusted for age, sex, surgery type and baseline body mass index, with credible differences inferred when the 95% credible interval of the standardized effect size excluded zero. Associations between outcomes were assessed using Pearson correlation. RESULTS: Of 443 eligible candidates, 58 participants (aged 18-65 years, 70% women, BMI 41.7 ± 4.4 kg/m(2)) were randomized to aerobic (n = 15), resistance (n = 13), combined (n = 14) or control (n = 16) groups, and 91.3% were included in the analysis. The combined exercise group preserved more FFM (-5.1 ± 2.8 kg vs. -7.7 ± 2.8 kg; ES 0.60 [0.41, 0.77]) and reduced more FM (-11.9% ± 5.7% vs. -10.1% ± 4.9%, ES -0.64 [-0.85, -0.40]) than control. Aerobic training most attenuated total hip BMD loss (-0.037 ± 0.033 g/cm(2), -3.3%) compared with control (-0.058 ± 0.021 g/cm(2), -5.4%; ES 0.69 [0.42, 0.92]) and modestly attenuated femoral neck BMD loss (ES 0.30 [0.11, 0.48]), with no differences at the lumbar spine. The relative increase in serum CTX was smaller in the aerobic (157.8%; ES -0.44 [-0.65, -0.18]) and combined groups (161.8%; ES -0.42 [-0.63, -0.17]) compared with control (196.4%). Physical function improved modestly, with aerobic training showing a greater improvement in walking distance than control (80.0 ± 56.4 m vs. 65.6 ± 39.2 m; ES 0.33 [0.08, 0.54]). Walking distance improvement correlated with weight loss. Handgrip strength was best preserved in the resistance group (ES 0.77 [0.47, 1.04]) and was positively correlated with protein intake. CONCLUSIONS: Following MBS, combined aerobic and resistance training improved body composition by preserving FFM and reducing FM, while aerobic training most attenuated bone loss. Exercise was associated with modest improvements in physical function, supporting individualized exercise strategies to promote metabolic, musculoskeletal and functional health after MBS. Trial Registration ClinicalTrials.gov Identifier: NCT04777305.