Increased Risk for Type 2 Diabetes in Relation to Adiposity in Middle-Aged Black South African Men compared to Women

Aims Despite a higher prevalence of overweight/obesity in black South African women compared to men, the prevalence of type 2 diabetes does not differ. We explored if this could be due to sex differences in insulin sensitivity, clearance and/or beta-cell function, and also sex-specific associations with total and regional adiposity. Methods This cross-sectional study included 804 black South African men (n=388) and women (n=416). Dual-energy x-ray absorptiometry was used to measure total and regional adiposity. Insulin sensitivity (Matsuda index), secretion (C-peptide index) and clearance (C-peptide/insulin ratio) were estimated from an oral glucose tolerance test. Results After adjusting for sex differences in fat mass index, men were less insulin sensitive and had lower beta cell function than women (p<0.001), with the strength of the associations with measures of total and central adiposity being greater in men than women (p<0.001 for interactions). Further, the association between total adiposity and type 2 diabetes risk was also greater in men than women (relative risk ratio (95% confidence interval): 2.05 (1.42– 2.96), p<0.001 vs. 1.38 (1.03–1.85), p=0.031). Conclusion With increasing adiposity, particularly increased centralisation of body fat linked to decreased insulin sensitivity and beta cell function, black African men are at greater risk for type 2 diabetes than their female counterparts.