Lower body subcutaneous fat accumulation and diabetes mellitus risk

Type II diabetes mellitus (DM) is associated with obesity. However, body fat distribution plays an important role in this disease's pathogenesis. The prevailing hypothesis is that a more central distribution of adipose tissue relative to peripheral locations is associated with DM. I hypothesized that preferential accumulation of subcutaneous adipose tissue in the lower body is associated with a lesser likelihood of insulin resistance (IR) and DM than when fat accumulates in a central distribution. This is independent of the body mass index (BMI) or waist circumference.

Upper and lower body circumferences and skinfold thickness were related to IR and DM in 7634 adults in the Third National Health and Nutrition Survey population that underwent oral glucose tolerance testing after an overnight fast. Logistic regression and contour analyses were used to determine the effect circumference and skinfold thickness measurements had on the presence of IR or DM. The various measurements were then stratified into BMI categories to refine the contribution each factor made to these diseases further.

Truncal subcutaneous fat correlated positively with IR and DM after correction for age and BMI. The thigh circumference and skinfold thickness correlated negatively. Regression and graphic analysis of the BMI-thigh skinfold thickness-IR relationship demonstrated that the greatest degree of IR occurred in the obese who had relatively small lower body adipose tissue depots. Those with large accumulations of lower body subcutaneous fat were less likely to have IR or DM.

The results of this study have shown that the accumulation of fat in lower body subcutaneous adipose tissue depots is associated with a lower likelihood of IR and DM than when it deposits in centrally located sites. Lower body peripheral fat may serve to buffer the effect of excess ingested energy, and central body fat may be involved in the pathogenesis of IR and DM. This effect was independent of overall adiposity in men and women and independent of waist circumference in men.