Introduction and purpose of the study
Bariatric surgery results in major weight loss, improvement of co-morbidities in obesity and physical capacity (VO 2 max). The evolution of habitual physical activity remains controversial, depending on the measurement tool: the declarative data (questionnaires) all indicate an increase in physical activity, the objective data (accelerometer-type motion counters) are in favor of a maintenance of physical activity after surgery. The relationships between physical activity and physical ability or body composition have been poorly studied. Our goals are to objectively measure the evolution of physical activity 6 months after a bypass gastric and analyze the relationship between physical activity, physical ability and body composition.
Material and methods
The study is part of the Promise project, a randomized controlled trial designed to optimize follow-up after gastric bypass , involving 94 severely obese women (2010 to 2014, nutrition service, Pitié-Salpêtrière). Usual physical activity was measured for 7 days before and 6 months after gastric bypass using an Actigraph GT3x accelerometer. Body composition was measured by DEXA absorptiometry and VO 2max in a maximal ergometer exercise stress test. Postoperative data were compared to preoperative data using the Wilcoxon (continuous variables) and McNemar (categorical variables) tests. The evolution of the VO 2max and body composition was analyzed according to the level of postoperative physical activity (Mann-Whitney).
We obtained valid data for 65 patients (age: 43.0 ± 10.1 years, preoperative BMI: 44.2 ± 6.0 kg / m 2 , duration of accelerometer wearing: ≥ 13 h / d) . Before gastric bypass, patients had an average of 27 ± 17 min/day of moderate-intensity physical activity, the majority of which were in very short-term sessions (14.3 ± 16.8% of physical activity performed in women). sessions of not more than 10 minutes). The minimum level of recommended physical activity (150 min/week of moderate-intensity physical activity, in sessions of at least 10 min) was achieved by 6% of patients. After the Gastric bypass, patients had an average of 34 ± 25 min/day of moderate intensity physical activity (+7 min/day, p < 0.05) and 17% reached the recommended level of physical activity. We observed interindividual variability: physical activity increased in 62% of patients and decreased in 37% of patients. The proportion of physical activity lasting at least 10 min increased after gastric bypass(19.6 ± 18.9%, p < 0.05). Patients practicing more than 150 min / week of moderate-intensity physical activity, compared to those practicing less, achieved a greater decrease in body fat percentage (-15.0 ± 6.7% vs. -11.6 ± 4.4% p < 0.05) and an increase in VO 2 max (+6.6 ± 25.4% vs. -0.9 ± 32.2%, p < 0.05).
Moderate intensity physical activity increases significantly after gastric bypass, but there is strong interindividual variability. The level of physical activity after gastric bypass is positively associated with changes in body composition and physical ability. The factors that may explain the favorable or unfavorable evolution of physical activity after surgery for obesity need to be better studied.