Glucose tolerance and hyperinsulinaemia in obese women: role of adipose tissue distribution, muscle fibre characteristics and androgens.

The separate independent statistical contribution of abdominal distribution of fat, hyperandrogenicity and muscle morphology to glucose intolerance and hyperinsulinaemia was analysed in 88 obese women. In univariate analyses the waist/hip circumference ratio (WHR), body fat and lean body mass were all positively associated, and SHBG levels were negatively associated with insulin and glucose values. Muscle fibre areas were positively correlated with insulin but not with glucose concentrations. Adjustment for other variables did not remove the positive association between WHR and fasting insulin and glucose concentrations. SHBG, free testosterone and type IIb fibre areas were, however, significant confounding factors in the relationship between WHR and summed insulin and glucose concentrations. We conclude that fat distribution in obese women is associated with fasting hyperglycaemia and hyperinsulinaemia, independently of androgens and muscle fibre morphology, but that reduced SHBG concentrations and increased type IIb fibre areas may partly explain increased glucose and insulin responses to an oral glucose load in abdominally obese women.