Phenotypic characteristics associated with insulin resistance in metabolically obese but normal-weight young women

Metabolically obese, normal-weight (MONW) individuals are a hypothesized su bgroup of the general population. These normal-weight individuals potential ly display a cluster of obesity-related features, although this has not, be en systematically tested in young women. me hypothesized that MONW young wo men would display higher levels of total and Visceral fat and lower levels of physical activity than normal women. In a cohort of 71 healthy nonobese women (21-35 years old), we identified MONW women based on cut points for i nsulin sensitivity (normal = glucose disposal >8 mg . min(-1) . kg(-1) offa l free mass [FFM], n = 58; impaired = glucose disposal <8 ml . min(-1) . kg (-1) of FFM, n = 13). Thereafter, we measured body composition (dual energy X-ray absorptiometry) and body fat distribution (computed tomography), car diorespiratory fitness (Vo(2max) on a treadmill), physical activity energy expenditure (doubly labeled water and indirect calorimetry), glucose tolera nce Coral glucose tolerance test), serum Lipid profile, and dietary intake. We found a higher body fat percentage (32 +/- 6 vs. 27 +/- 6%, P = 0.01) a nd higher subcutaneous (213 +/- 61 vs. 160 +/- 78 cm(2), P = 0.03) and visc eral (44 +/- 16 vs. 35 +/- 14 cm(2), P < 0.05) abdominal adiposity in the M ONW group versus the normal group. The MONW group showed a lower physical a ctivity energy expenditure (2.66 +/- 0.92 vs. 4.39 +/- 1.50 MJ/day, P = 0.0 1), but no difference in cardiorespiratory fitness was noted between groups . In conclusion, despite a normal body weight, a subset of young, apparentl y healthy women displayed a cluster of risky phenotypic characteristics tha t, if left, untreated, may eventually predispose them to type 2 diabetes an d cardiovascular disease.