Insulin secretion in metabolically obese, but normal weight, and in metabolically healthy but obese individuals

Metabolically obese but normal-weight (MONW) individuals present metabolic disturbances typical of obese individuals. Additionally, metabolically healthy but obese (MHO) individuals have been identified who are relatively insulin sensitive and have a favorable cardiovascular risk profile. We compared insulin secretion patterns of MONW and MHO with those of two age-matched groups comprising nonobese individuals or obese insulin-resistant subjects, respectively. To this end, 110 nonobese subjects and 87 obese subjects were stratified into quartile based on their insulin-stimulated glucose disposal (M(FFM)). Insulin secretion was estimated by acute insulin response (AIR) during an intravenous glucose-tolerance test (IVGTT), and the disposition index was calculated as AIR x M(FFM). We found that, as defined, M(FFM) was lower in MONW, who exhibited higher triglycerides, free-fatty acid (FFA), and 2-h postchallenge glucose levels compared to normal nonobese group. Insulin secretion was higher in MONW than in normal nonobese subjects, but disposition index was lower in MONW. Disposition index did not differ between MONW and insulin-resistant obese. M(FFM) was higher in MHO who exhibited lower waist circumference, blood pressure (BP), triglycerides, FFA, insulin levels, and higher high-density lipoprotein (HDL) cholesterol compared to insulin-resistant obese. Insulin secretion did not differ between insulin-resistant obese and MHO, but disposition index was lower in the former group. In conclusion, MONW and insulin-resistant obese showed decreased compensatory insulin secretion compared to normal nonobese and MHO subjects, respectively. Because these subjects also exhibited a worse metabolic risk profile, these findings may account for their increased risk for type 2 diabetes.