Relationship Of Leptin,Body Composition And Resting Metabolic Rate In Chinese Overweight And Obese Adults

Abstract

PURPOSE: Resting metabolic rate (RMR) and substrate utilization are important factors in maintaining energy balance and leptin is postulated to be involved in the regulation of body weight. However, in overweight and obese individuals, excess fat mass has a significant impact on metabolic function both directly through altered metabolic rate and substrate oxidation, and indirectly, through chronic changes in hormonal concentrations. This study determined the relationship of body composition and leptin with RMR and substrate utilization (carbohydrate, fat and protein oxidation rates) in Chinese overweight and obese adults. METHODS: The subjects were 33 women (age = 44.0±12.1 years; BMI =27.9±3.2 kg/m2; percent body fat (%fat) = 38.7 ± 4.0%) and 34 men (age= 30.0±9.7years; BMI=27.4±1.7 kg/m2; percent body fat (%fat) = 27.5 ± 4.3%). RMR and substrate utilization were measured by indirect calorimetry (Metamax 3B® Metabolic Measurement system, German) and body composition by the bioelectrical impedance method. Serum leptin levels were determined by radioimmunoassay. RESULTS: In men and women, RMR significantly correlated with Skeletal Muscle Mass (Men: R=0.556, p=0.001; Women: R=0.493, p=0.004), but both not significantly correlated with leptin(both p>0.05). In stepwise multiple regression analysis, SMM was the main predictor of RMR, explaining 42.5% and 28.5% of the variance of RMR in men and women respectively. In women, but not men, leptin significantly correlated with RER (R=-0.581, p=0.029) and carbohydrate, fat, and protein oxidation rates respectively (R=-0.558, 0.689, 0.690; all p<0.01).Furthermore,in stepwise multiple regression analysis, leptin explaining 33.7% of the variance of RER in women. CONCLUSIONS: Skeletal Muscle Mass is a significant predictor of RMR in Chinese overweight and obese adults, evaluation of body composition may be an effective and efficient way to evaluate metabolic status. Serum leptin concentrations in female subjects showed a negative association with respiratory quotient and carbohydrate oxidation rate and positive association with fat and protein oxidation rates. We suggest that sex-specifc evaluations are also necessary. Acknowledgements: This work was supported by National science and technology program of China (Grants No.2013FY114700)