Resting Metabolic Rate, Total Daily Energy Expenditure, and Metabolic Adaptation 6 Months and 24 Months After Bariatric Surgery.

Abstract

ObjectiveLittle is known about long-term metabolic (energy expenditure) adaptation after bariatric surgery.MethodsResting metabolic rate under basal conditions (RMR), total daily energy expenditure (TDEE) and body composition were measured in 25 participants in the Longitudinal Assessment of Bariatric Surgery-2 (LABS-2).ResultsSix months after surgery, BMI (±SD) decreased (47 ± 6 to 37 ± 5 kg/m2), body fat from 48 ± 6 to 40 ± 6% fat and fat-free mass from 67 ± 9 to 60 ± 9 kg. In absolute terms RMR and TDEE both decreased significantly (1730 ± 278 vs. 1430 ± 200 and 2879 ± 544 vs. 2369 ± 304 kcal/day) and the achieved energy balance was −1293 ± 355 kcal/day. Sixteen of these participants underwent repeated measures at ~24 months; TDEE decreased 6 months postoperative (2957 ± 540 kcal/day to 2423 ± 324, P=0.0003), but at ~24 months, TDEE (2602 ± 471 kcal/day) was not significantly different compared to Month 6. The average negative energy balance from Baseline to Month 24 was −379 ± 131 kcal/day.ConclusionsRMR and TDEE fall precipitously in the first six months after bariatric surgery but these adaptive changes were no longer significant after two years.