Prevalence and features of impaired glucose tolerance in young underweight Japanese women.

Objective In Japan, while it is known that underweight women over the age 40 years have a high risk for type 2 diabetes, there is a lack of clarity on the association between glucose tolerance and underweight in younger women. Accordingly, we aimed to investigate the prevalence and features of impaired glucose tolerance (IGT) in young Japanese underweight women. Designs and methods In this cross-sectional study, we recruited 56 normal weight and 98 underweight young Japanese women and evaluated their glucose tolerance levels using an oral glucose tolerance test. Then, we compared the clinical characteristics associated with normal glucose tolerance (NGT) and IGT in the underweight women. Insulin secretion, whole-body insulin sensitivity, and adipose tissue insulin resistance values were measured using the insulinogenic index, whole-body insulin sensitivity index (Matsuda index), and adipose insulin resistance index (Adipo-IR), respectively. Fitness level (peak VO2) was measured using an ergometer. Results The prevalence of IGT was higher in the underweight women than the normal weight women (13.3% vs 1.8%). The underweight women with IGT showed a lower insulinogenic index, lower peak VO2 and Matsuda index, and a higher fasting free fatty acid level and Adipo-IR than those with NGT. The whole-body composition was comparable between the NGT and IGT groups. Conclusions The prevalence of IGT was higher in young Japanese women with underweight than those with a normal weight. The underweight women with IGT showed impaired early-phase insulin secretion, low fitness levels, and reduced whole-body and adipose tissue insulin sensitivity levels.