Background: Weight loss is associated with a decrease in both energy expenditure and circulating leptin levels. Whether this holds true when the influence of body composition on energy expenditure and leptin is taken into account remains controversial. The aim of the study was to assess changes in resting metabolic rate (RMR) and serum leptin adjusted for body composition during surgically induced weight loss.
Methods: In 36 women (age 42.7+/-8.7 years; BMI 47.2+/-8.5 kg/m(2); mean+/-SD) undergoing laparoscopic adjustable gastric banding (LAGB) for morbid obesity, we measured RMR (by indirect calorimetry), body composition (by dual-energy X-ray absorptiometry) and serum leptin (by immunoradiometry), immediately before and 1 year after surgery.
Results: 1 year after LAGB, there were significant decreases in body weight (-23.7+/-11.6 kg, P<0.001), fat mass (FM: -20.9+/-11.3 kg, P<0.0001), lean body mass (LBM: -3+/-5.3 kg, P=0.005), RMR (-298+/-309 kcal/day, P<0.0001), serum leptin (-24.0+/-18.4 ng/ml, P<0.0001), RMR/LBM ratio (-3.9+/-5.8 kcal/kg LBM/day, P<0.01) and leptin/FM ratio (-0.21+/-0.29 ng/kg FM/ml, P<0.001). RMR values after surgery were correctly predicted by the regression equation relating RMR to LBM and FM at baseline, whereas this was not the case for serum leptin (in relation to FM).
Conclusions: Changes in RMR 1 year after LAGB were explained by changes in body composition whereas changes in serum leptin were not. The data provide no evidence for a metabolic adaptation of RMR with weight loss, but suggest that serum leptin is decreased beyond expected values based on body composition, a factor that may favor weight regain after surgically induced weight loss.