Leptin levels are associated with fat oxidation and dietary-induced weightloss in obesity

Objective: To examine the relationship between fasting plasma leptin and 24 -hour energy expenditure (EE), substrate oxidation, and spontaneous physica l activity (SPA) in obese subjects before and after a major weight reductio n compared with normal weight controls. To test fasting plasma leptin, subs trate oxidations, and SPA as predictive markers of success during a standar dized weight loss intervention. Research Methods and Procedures: Twenty-one nondiabetic obese (body mass in dex: 33.9 to 43.8 kg/m(2)) and 13 lean (body mass index: 20.4 to 24.7 kg/m( 2)) men matched for age and height were included in the study. All obese su bjects were reexamined after a mean weight loss of 19.2 kg (95% confidence interval: 15.1-23.4 kg) achieved by 16 weeks of dietary intervention follow ed by 8 weeks of weight stability. Twenty-four-hour EE and substrate oxidat ions were measured by whole-body indirect calorimetry. SPA was assessed by microwave radar. Results: In lean subjects, leptin adjusted for fat mass (FM) was correlated to 24-hour EE before (r = -0.56, p<0.05) but not after adjustment for fat free mass. In obese subjects, leptin correlated inversely with 24-hour and resting nonprotein respiratory quotient (r = -0.47, p<0.05 and r = -0.50, p <0.05) both before and after adjustments for energy balance. Baseline plasm a leptin concentration, adjusted for differences in FM, was inversely relat ed to the size of weight loss after 8 weeks (r = -0.41, p = 0.07), 16 weeks (r = -0.51, p<0.05), and 24 weeks (r = -0.50, p < 0.05). Discussion: The present study suggests that leptin may have a stimulating e ffect on fat oxidation in obese subjects. A low leptin level for a given FM was associated with a greater weight loss, suggesting that obese subjects with greater leptin sensitivities are more successful in reducing weight.