Metabolic consequences of obesity and body fat pattern: lessons from migrant studies.

Prevalence of non-insulin-dependent diabetes mellitus and mortality from coronary heart disease are higher in people of South Asian (Indian, Pakistani and Bangladeshi) descent living in urban societies than in other ethnic groups. The high prevalence of diabetes is one manifestation of a pattern of metabolic disturbances related to central obesity and insulin resistance, which includes raised plasma very low density lipoprotein triglyceride and low plasma high density lipoprotein-cholesterol. Average waist/hip circumference ratios are higher in South Asians than in Europeans of similar body mass index: in this respect South Asians differ from other populations such as Pima Indians where high prevalence of non-insulin-dependent diabetes mellitus occurs in association with generalized obesity. The high rates of coronary heart disease in South Asians are most easily explained by the effects of this central obesity/insulin resistance syndrome, although ethnic differences in fasting lipids are unlikely to account fully for the excess risk. In Afro-Caribbean migrants, the prevalence of diabetes is almost as high as in South Asians but the lipid disturbances characteristic of the insulin resistance syndrome do not occur to the same extent. This may account for the low rates of coronary heart disease in this group.