Association of Physical Activity with Change in Weight and Percentage Body Fat Following Bariatric Surgery

Abstract

PURPOSE: To examine the association of objectively-measured physical activity (PA) with change in weight and percentage body fat (%BF) one year (1-yr) following bariatric surgery. METHODS: The Longitudinal Assessment of Bariatric Surgery-2 (LABS-2) is a 10-center prospective study examining long-term outcomes following bariatric surgery. Of 2458 LABS-2 participants, 451 were given an activity monitor, which records steps/minute, pre- and 1-yr post surgery. Steps/day was calculated for participants who wore the monitor ≥10 hours/day for ≥3 days and had body composition measured via bioimpedance at both time points (n=277). General linear models tested whether change in PA from pre- to post-surgery and, separately, post-surgery PA, were independently associated with changes in weight and %BF from pre- to 1-yr post-surgery, controlling for days from surgery to post-surgery measurements, surgical procedure, age, sex, and either pre-surgery weight or %BF, respectively. RESULTS: Most participants (78% female, 19-76 years, pre-op BMI 34.3-70.4 kg/m2) underwent gastric bypass (70%) or adjustable gastric banding (21%). Mean weight was 131.2 ± 25.2 kg pre-surgery and 92.20 ± 21.9 kg post-surgery. Mean %BF was 50.0 ± 5.7% pre-surgery and 36.2 ± 8.8% post-surgery. 3000 additional steps/day pre- to post-surgery was significantly associated with a 1.5 kg decrease in weight (p=.04), and a 1.1% decrease in %BF (p=.02). Post-surgery PA, as opposed to change in PA, was not significantly related to change in weight (p=.36), but was significantly related to change in %BF; 3000 steps/day post-surgery was associated with 1.5% decrease in %BF (p<.001). CONCLUSION: This observational study found that both increasing PA from pre to 1-yr post-surgery and a higher post-surgery PA level were independently associated with favorable changes in body composition in the first year following bariatric surgery. Randomized studies are needed to determine whether increasing the PA of bariatric surgery patients improves weight loss and body composition outcomes. Funding: This research was funded with a grant from the National Institute of Diabetes and Digestive and Kidney Diseases.