Energy expenditure, metabolic adaptation, physical activity and energy intake following weight loss: comparison between bariatric surgery and low-calorie diet.

Objective: Bariatric surgery remains the most effective treatment to achieve substantial weight loss; however, total daily energy expenditure and physical activity changes in response to such interventions have been seldom explored.

Methods: In this prospective observational study, total daily energy expenditure (TDEE) using doubly labeled water and physical activity (SenseWear armband) was assessed in 17 females (mean ± SD: 48.6 ± 9.7 kg/m2, 43 ± 12 years) at baseline and 8 and 52 weeks following either bariatric surgery (BSG, N = 9) or a low-calorie diet (LCD, N = 8). Energy intake was assessed using the intake-balance method.

Results: After 8 weeks, weight loss was 16.0 ± 3.5 kg and TDEE decreased by 552 ± 319 kcal/d in BSG (P < 0.001) compared to 8.8 ± 3.4 kg and 256 ± 239 kcal/d in LCD (P < 0.05). After 52 weeks, weight loss was 44.3 ± 16.4 kg and TDEE decreased by 583 ± 418 kcal/d (P < 0.001), compared to 4.3 ± 6.7 kg and 84 ± 285 kcal/d in LCD (P > 0.05). TDEE was lower than predicted in BSG at 8 (P = 0.03) but not 52 weeks (P = 0.77). There was no evidence of metabolic adaptation in LCD. Average daily energy intake in BSG was 1403 ± 245 kcal/d compared to 2545 ± 398 kcal/d in LCD (P < 0.001). In BSG, step count and physical activity minutes were increased at 52 weeks compared to baseline (P = 0.03), whereas no significant changes were observed in LCD.

Conclusion: Bariatric surgery-induced weight loss decreased TDEE at 8 weeks and 1 year, resulting in metabolic adaptation after 8 weeks that was reversed at 1 year. These changes were accompanied by an increase in physical activity.