Baseline body fat and fat distribution predicts T2D risk 11 years later in black SA women
A.Mtintsilana1, L. Micklesfield1, E. Chorell2, T. Olsson2, J. Goedecke1,3

1South African Medical Research Council/University of the Witwatersrand Developmental Pathways for Health Research Unit, Department of Paediatrics, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa,
2Umea University, Department of Public Health and Clinical Medicine, Umeå University, Umeå, Sweden, Umea, Sweden.
3South African Medical Research Council, Non-Communicable Disease Research Unit, South African Medical Research Council, Cape Town, South Africa, Cape Town, South Africa

Background: Central body fat distribution, specifically visceral adipose tissue (VAT), has been strongly associated with insulin resistance (IR) and type 2 diabetes (T2D). However, several cross-sectional studies from South Africa (SA) have shown that black SA women have less VAT and more abdominal and gluteal subcutaneous adipose tissue (SAT) than their white counterparts, despite being more insulin resistant (IR).
Aim: This longitudinal study aimed to investigate whether baseline and/or change in body fat and its distribution predict T2D risk in black SA women, 11 years later.
Method: A convenience sub-sample (n=144) of black SA women from the Birth to Twenty (Bt20) caregiver cohort was recruited for this study. Participants were eligible for inclusion if they fulfilled the criteria of being an African woman and resident in the urban township of Soweto, less than 65 years of age, HIV negative and willing to be tested for HIV. Whole body fat mass (FM) and body fat distribution, including trunk FM, leg FM and VAT were measured using dual-energy x-ray absorptiometry (DXA) at baseline (age: 42 ± 6.7 and 11 ± 1.1 years later. At follow-up, fasting glucose and insulin concentrations were measured and participants completed an oral glucose tolerance test (OGTT), from which insulin resistance (HOMA-IR) and insulin sensitivity (Matsuda index) were determined. 

Results: Body weight and whole body fat mass (FM) increased by 7.0 ± 9.0 kg and 5.6 (0.9-12.9) kg, respectively, over the follow-up period (P<0.001). In addition, trunk FM increased by 4.2%, leg FM by 2.4% and VAT by 43% (P<0.001). Independent of age and FM, baseline trunk FM was associated with 65% increased risk for the progression of NGT to IGT and 2.64 times increased risk for the progression of NGT to T2D (P<0.001). Baseline VAT was associated with 1% and 2% increased risk for progression of NGT to IGT, and T2D, respectively (P<0.05). Furthermore, whole body FM and central FM (trunk and VAT) were associated with increased HOMA-IR, accounting for 7-13% of the variance in HOMA-IR (P<0.001). Whole body FM and trunk FM were also significantly associated with reduced insulin sensitivity, and accounted for 4-9% variance in insulin sensitivity.  In contrast,  baseline leg FM was associated with a 38% and 58% significant decrease in the risk of developing IGT and T2D, respectively (P <0.001). Moreover, baseline leg FM was negatively and positively associated with HOMA-IR and insulin sensitivity, and accounted for 12% and 7% of the variance in HOMA-IR and insulin sensitivity, respectively. 


Discussion: Baseline, rather than the change in body fat and fat distribution, predicted measures of T2D risk 11 years later. Specifically, measures of central FM (i.e. trunk and VAT) were associated with reduced insulin sensitivity and increased risk for the progression of NGT to IGT, and T2D. In contrast, baseline peripheral FM (i.e. leg FM) was associated with increased insulin sensitivity and reduced risk for the progression of NGT to IGT, and T2D.  Prevention of obesity, in particular the prevention of centralization of body fat, is essential to reduce the risk of developing T2D in black South African women.

Baseline body fat and fat distribution predicts T2D and CVD risk 11 years later in black SA women