Body fat distribution and hyperinsulinemia as risk factors for diabetes and cardiovascular disease.

Differences in body fat distribution between diabetics and nondiabetics have been recognized for several decades; diabetics have a more centralized or upper body fat pattern than nondiabetics. Recently, attention has focused on fat patterning and also on hyperinsulinemia as possible risk factors for cardiovascular disease, as well. The case for insulin as a cardiovascular risk factor is bolstered by theoretical considerations related to its possibly atherogenic effects on serum and arterial wall lipids. Empirical evidence for fat patterning and hyperinsulinemia as cardiovascular risk factors rests on six prospective epidemiologic studies, three on fat patterning and three on insulin. Although provocative, none of these studies can be regarded as definitive. In none was a dose-response effect demonstrated, and there are various inconsistencies within and across the studies. Moreover, in none of the studies were hyperinsulinemia and fat patterning evaluated simultaneously. This is of particular importance in view of the well-documented interrelationships between these two variables. For example, insulin resistance and hyperinsulinemia have been found to be greater in women with upper body obesity compared to women with lower body obesity of equivalent degree. Considerable progress has been made recently in understanding the mechanisms of the differential metabolic effects of these two types of obesity. The extent to which fat patterning and hyperinsulinemia are genetic or acquired has received relatively little attention. Further research on this question is warranted since elucidation of any environmental influences on these variables might suggest new clinical and public health control measures.