Background: Exercise training optimizes cardiorespiratory fitness (CRF) after bariatric surgery, but the effect of spontaneous physical activity is not well known. This study aimed to objectively quantify changes in CRF and habitual physical activity 6 months after bariatric surgery and to examine whether change in CRF was related to change in physical activity.
Methods: Secondary analyses were performed on data from women who underwent Roux-en-Y gastric bypass (RYGB) between 2010 and 2014. Measurements were performed before and 6 months after RYGB and included V̇O2peak (graded maximal exercise test on a cycle ergometer), habitual physical activity (Actigraph GT3x accelerometer worn during 7 days), and body composition (DXA absorptiometry). Changes after RYGB were analyzed using Wilcoxon signed-rank test. Relations between change in CRF and change in physical activity were analyzed with Spearman correlations adjusted on age and preoperative BMI.
Results: Forty-five women (median [P25-P75] age, 43.0 [38.0-51.0] year; BMI, 42.6 [40.0-45.5] kg/m2) were included. Mean (SD) weight loss 6 months after RYGB was - 27.5 (7.9) kg (P < 0.001). Absolute V̇O2peak decreased by 0.35 (0.50) L/min (P < 0.001) and relative V̇O2peak tended to increase by 1.7 (5.3) mL/kg/min (P = 0.06), both with large inter-individual variability. Based on objective accelerometry data, daily steps and moderate-to-vigorous physical activity increased by 1275 (3164) steps/day and 7.6 (19.3) min/day, respectively (both P < 0.05). Change in absolute V̇O2peak was positively related to change in moderate-to-vigorous physical activity (r = 0.35; P = 0.03).
Conclusions: The decrease in absolute CRF observed 6 months after RYGB might be prevented by increasing habitual physical activity.
Trial registration: clinicaltrials.gov identifier: NCT01113996.
Keywords: Accelerometry; Gastric bypass; Obesity; Physical activity patterns; Physical fitness; V̇O2max.