Resting energy expenditure in insulin resistance falls with decompensation of insulin secretion in obese children

Background: Low resting energy expenditure (REE) and respiratory quotient (RQ) have been shown in adults to predispose to obesity and diabetes mellitus. Aim: To correlate REE and RQ in 73 obese children and young adults (body mass index [BMI] 37 ± 10 kg/m²) with measures of insulin secretion and resistance (IR) indices, percent carbohydrate and fat oxidation, and prolactin and leptin levels. Design: During a 3-day admission, REE and RQ were determined by indirect calorimetry. Blood chemistries and oral glucose tolerance test (OGTT) were obtained, and intravenous glucose tolerance test (IVGTT) modified by tolbutamide was conducted after an overnight fast, permitting calculation of acute insulin response (AIR), insulin resistance (Si_IVGTT), and disposition index (DI). Results: Patients fell into two groups according to their Si_IVGTT: those with normal insulin sensitivity (NIS) and those with insulin resistance (IR). IR patients were subdivided on the basis of DI (cut-off value 0.13 min^-1) into compensated (CIR) or decompensated (DIR) groups. CIR patients had higher RQ, REE corrected by BMI, AIR, and carbohydrate oxidation and lower fat oxidation than NIS and DIR patients. REE correlated positively with BMI, leptin, and AIR, and negatively with Si_IVGTT. Conclusions: Findings in the CIR and DIR groups support the correlation of REE with metabolic changes consistent with an increased risk of diabetes mellitus.