Temporal Association Between Body Composition and Functional Capacity on Long Term Follow-Up of Bariatric Surgery

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Background: Severe obesity reduces functional capacity. Total and segmental body composition after bariatric surgery may more accurately estimate functional capacity as assessed by the 6-minute walk test (6MWT) than the body mass index(BMI). Objective: To correlate the distance walked during 6MWT(6MWD) with BMI and body composition in the early (T1:6 months) and late (T2:36 months) postoperative period of bariatric surgery. Methods: Functional capacity was evaluated in 77 patients classified according to obesity grade before bariatric surgery(T0) in: Morbidly obese(MO: BMI 40 to 49.9 kg/m2) and super obese(SO: BMI 50 to 59.9 kg/m2) and according to the percentage of excess weight loss(%EWL) in T2: success group(SG: EWL≥50%) and failure group(FG: EWL<50%). Results: A significant increase (p<0.001) was found in the 6MWD between T0/T1 and T0/T2. There was also an increase (p<0.05) of the 6MWD between T0/T1 and T0/T2 in MO and SO participants, with no significant difference (p>0.05) between T1/T2 in both groups. There was a significant increase (p<0.05) in 6MWD between T0/T2 in SG and FG participants. No significant difference (p>0.05) was found in the 6MWD between MO/SO and SG/FG. At all times and groups, the 6MWD showed a moderate correlation (p<0.05) with the percentage of fat free mass (FFM%) and fat free mass of lower limbs (FFMLL%) but not with BMI. Conclusion: Fat free mass (FFM) indicate better functional capacity on long-term follow-up after bariatric surgery independently of obesity grade or successful weight loss. BMI is not the best predictor of functional capacity.