Body composition displays expected and unexpected contributions to blood pressure and glycemia in young South African women

Introduction Sub-Saharan Africa is undergoing rapid demographic, sociocultural, and economic transitions that are contributing to rising rates of overweight/obesity, which in turn may drive cardiometabolic sequelae such as diabetes and hypertension. However, the extent to which excess adiposity may contribute to the prevalence of such sequelae in sub-Saharan Africa remains uncertain. We thus sought to systematically evaluate body composition by dual-energy X-ray absorptiometry (DEXA) and its associations with glycemia and blood pressure (BP) in young women in Soweto, South Africa. Research design and methods This study was performed in 7735 women (median age of 22.4 years) undergoing assessment for a clinical trial. Whole-body DEXA scan yielded 12 measures of body composition (reflecting whole-body fat, central adiposity, peripheral adiposity, and lean mass/soft tissue) that were assessed as predictors of A1c, systolic BP, and diastolic BP, respectively. Results The study population had high rates of overweight/obesity (49.6%), pre-diabetes/diabetes (10.9%), and hypertension (11.9%). While specific adiposity measures (fat mass (FM), visceral adipose tissue, subcutaneous adipose tissue (SAT), android fat) were significantly associated with A1c, these associations were exceedingly modest, with these measures additionally explaining only 0.14% to 0.37% of the variance in A1c. In contrast, all 12 body composition measures showed significant associations with systolic BP and diastolic BP. Indices of lean mass/soft tissue (lean mass index, lean mass, fat-free soft tissue mass) explained 5.8% to 6.3% of the variance in systolic BP, while measures of adiposity (android fat, SAT, FM) reconciled 4.6% to 4.8% of the variance in diastolic BP, reflecting much stronger associations with BP than with A1c. Conclusion In this young adult population with high rates of overweight/obesity and pre-diabetes/diabetes, DEXA-derived adiposity exhibits modest associations with glycemia, underscoring the atypical nature of diabetes in sub-Saharan Africa. Trial registration number PACTR201903750173871.