The role of obesity in the association of cardiovascular risk factors and glucose intolerance in small Japanese and North American communities

To investigate whether the influence of obesity on cardiovascular risk factors and glucose intolerance differs between Japan and the US, we conducted cross-sectional surveys in those with elevated plasma glucose in Tanushimaru, Japan, and a stratified random population sample, in Wadena, MN. Subjects numbered 204 in Tanushimaru and 334 in Wadena. Body mass index (BMI), blood pressure, blood lipids, fasting plasma levels of glucose, glycosylated hemoglobin A(1c,) insulin, and free fatty acids were assessed. Overweight was defined as BMI of 27.5-29.9 kg/m(2) and obesity as BMI> or =30 kg/m(2). Gradual increases in risk factors were seen as BMI increased in both studies. Most risk factors were associated with glucose intolerance, except for BMI in Tanushimaru. In Wadena, glucose intolerance increased sharply among the obese. Adjustment for BMI attenuated the associations of cardiovascular risk factors with glucose intolerance in Wadena, but not in Tanushimaru. Obesity has an exaggerated influence on risk factors, compared with being overweight. The associations of glucose intolerance with cardiovascular risk factors are more affected by adjustment for BMI in Wadena than in Tanushimaru, not because of a different influence of body weight on risk factors between the two cities, but because obesity is rare in Japan.