Does endogenous GLP-1 affect resting energy expenditure and fuel selection in overweight and obese adults?

PURPOSE: To investigate the association between fasting glucagon-like peptide 1 (GLP-1) levels and resting energy expenditure (REE), and respiratory quotient (RQ) in overweight and obese adults. METHOD: Study participants were enrolled at the Dietetic and Metabolic Unit, University of Pavia, Italy. Inclusion criteria were age ≥ 25 and ≤ 45 years, and body mass index (BMI) ≥ 25 and ≤ 35 kg/m2. Diabetic subjects were excluded. Body composition was measured by dual-energy X-ray absorptiometry. REE was evaluated using indirect calorimetry, and RQ was calculated from respiratory gas exchanges. Fasting GLP-1, glucose, insulin and free fatty acid (FFA) levels, and 24-h norepinephrine urinary excretion were measured. Homeostasis model assessments of insulin resistance (HOMA-IR) and beta-cell function (HOMA-β) were calculated. RESULTS: Thirty-seven participants were included (age 43.4 ± 1.6 years; BMI 30.6 ± 0.5 kg/m2). REE was not associated with fasting GLP-1 levels (p = 0.98) after adjustment for age, sex, fat-free mass (FFM), and fat mass (FM). Similarly, no association was observed between RQ and GLP-1 levels (p = 0.95), after adjustment for age, sex, and body fat. CONCLUSION: In adults subjects with increased adiposity fasting, GLP-1 levels do not seem to play a role in the regulation of energy metabolism and in fuel selection.