Metabolic adaptation following massive weight loss is related to the degree of energy imbalance and changes in circulating leptin

Objective To measure changes in resting metabolic rate (RMR) and body composition in obese subjects following massive weight loss achieved via bariatric surgery or calorie restriction plus vigorous exercise. Methods Body composition and RMR were measured in 13 pairs of obese subjects retrospectively matched for sex, body mass index, weight, and age who underwent either Roux‐en‐Y gastric bypass surgery (RYGB) or participated in “The Biggest Loser” weight loss competition (BLC). Results Both groups had similar final weight loss (RYGB: 40.2 ± 12.7 kg, BLC: 48.8 ± 14.9 kg; P = 0.14); however, RYGB lost a larger proportion of their weight as fat‐free mass (FFM) (RYGB: 30 ± 12%, BLC: 16 ± 8% [P