Association of increased physical activity with greater fat mass loss following metabolic bariatric surgery: A longitudinal observational study

Metabolic bariatric surgery (MBS) is an effective treatment for weight loss, but a significant proportion of patients undergoing MBS experience weight regain or muscle loss. Exercise is recommended for patients undergoing MBS, but inconsistent outcomes have been reported on the effect of exercise on weight loss. This study investigated the association between increased physical activity and the changes in weight and body composition of Korean subjects with obesity after MBS. This study prospectively analyzed 78 subjects who underwent MBS from April 2019 to April 2022. The levels of physical activity were assessed using self-report questionnaires before and one year after MBS. Physical activity-related energy expenditure (MET-min/week) was calculated by multiplying the frequency, intensity, and duration of activities. Subjects were classified into two groups based on changes in physical activity levels before and after surgery: the MET-non-increased group and the MET-increased group. Body composition was analyzed by bioimpedance analysis. The mean age of the subjects was 41.7 ± 10.2 years, 31 (39.7%) were male, and baseline weight and body mass index (BMI) were 104.6 ± 19.4 kg and 37.7 ± 5.5 kg/m², respectively. The MET-increased group had a significantly greater reduction in weight, BMI, and fat mass (FM) after MBS compared to the MET-non-increased group (weight, -32.2 ± 13.0 kg vs. -25.6 ± 9.3 kg, P = 0.015; BMI, -11.7 ± 4.5 kg/m² vs. -9.1 ± 3.0 kg/m², P = 0.005; FM, -27.0 ± 11.2 kg vs. -19.4 ± 7.5 kg, P = 0.002). However, no significant difference was observed in the change in muscle mass between the two groups. A greater increase in of physical activity and exercise level was associated with a greater reduction in weight (ß = -0.263, P = 0.003) and fat mass (ß = -0.292, P = 0.003) after MBS when age, sex, BMI, HbA1c, and baseline metabolic parameters were adjusted. Increased physical activity after MBS was associated with a greater reduction in weight and body fat. Emphasizing increasing physical activity is a key component for maximizing the benefits of MBS.