CENTRAL ADIPOSITY AND ITS METABOLIC CORRELATES IN OBESE ADOLESCENT GIRLS

To establish whether alterations in insulin action and secretion and t heir relationship to body fat distribution occur early in the course o f developing obesity, we studied 14 obese adolescent girls [13.2 +/- 0 .7 yr, body mass index (BMI) 32 +/- 1.4], 16 nonobese adolescent girls (12.5 +/- 0.6 yr, BMI 21.0 +/- 0.8), and 14 nonobese young women (24. 0 +/- 0.6 yr, BMI 21.0 +/- 0.9). Insulin action was assessed by a sequ ential two-step (8 and 40 mU . m(-2). min(-1)) euglycemic insulin damp in combination with [1-C-13]glucose and indirect calorimetry. Insulin secretion was determined by the hyperglycemic clamp technique (6.9 mm ol/l). Magnetic resonance imaging was used to quantify visceral and su bcutaneous abdominal fat depots. In obese girls, an impairment in gluc ose disposal was present with both insulin doses; at the higher dose, rates of glucose uptake were reduced by 30% in nonobese girls (240 +/- 30 vs. 340 +/- 19 mg . m(-2). min(-1), P < 0.05) and by an additional 29% (170 +/- 17 mg . m(-2). min(-1), P < 0.05) in obese girls. Insuli n infusion failed to stimulate glucose oxidation and to suppress lipid oxidation only in obese girls. Suppression of free fatty acid levels, but not hepatic glucose production, was decreased in obese girls comp ared with controls. Fasting and glucose-stimulated insulin responses w ere greater in obese than in nonobese adolescents, who, in turn, had g reater responses than lean women. In obese girls, visceral fat, but ne ither waist-to-hip circumference ratio nor subcutaneous fat, was highl y correlated with basal insulin secretion (r = 0.89, P < 0.001), stimu lated insulin secretion (r = 0.61, P < 0.05), and insulin resistance ( r = -0.87, P < 0.02). Increased visceral fat, hyperinsulinemia, and in sulin resistance (involving glucose and Lipid metabolism) are closely linked abnormalities that are expressed early in the natural history o f obesity. Adolescents with central adiposity should be targeted for w eight reduction and health surveillance to reduce morbidity of adult o besity.