Higher baseline fat oxidation promotes gynoid fat mobilization in response to a 12-week exercise intervention in sedentary, obese black South African women.

Abstract

This 12-week exercise intervention study assessed changes in cardiorespiratory fitness (CRF), energy expenditure (EE), and substrate utilisation at rest and during exercise in obese, black South African (SA) women and explored associations with changes in body composition. Black SA women (body mass index: 30-40 kg·m-2, age: 20-35 years) were randomised into control (CTL; n = 15, maintaining usual activity) or exercise (EXE; n = 20; 12 weeks, 4 days·week-1, 40-60 min·day-1 at >70% peak heart rate) groups. Pre- and post-intervention testing included peak oxygen consumption, resting and steady state (50% peak oxygen consumption) EE, respiratory exchange, and body composition (dual-energy X-ray absorptiometry). Dietary intake (4-day) and daily step-count (ActivPAL, activPAL3c; PAL Technologies Ltd, Glasgow, UK) was collected at pre-testing and at 4, 8, and 12 weeks. EXE increased peak oxygen consumption (24.9 ± 2.4 to 27.6 ± 3.4 mL·min-1·kg-1; p < 0.001) and steady state fat oxidation rates (7.5 ± 2.5 to 9.0 ± 2.7 mg·min-1·kg-1 fat-free soft tissue mass; p = 0.003) (same relative exercise intensity). CTL remained unchanged (p > 0.05). EXE reduced proportional gynoid fat mass (percentage total fat mass, p = 0.002). Baseline resting carbohydrate oxidation rates (p = 0.036) and steady state fat oxidation rates (p = 0.021) explained 60.6% of the variability in Δgynoid fat mass (p < 0.001) in EXE. This 12-week exercise intervention improved CRF and steady state fat oxidation rates. Greater reliance on fat oxidation at baseline promoted proportional reductions in gynoid, not visceral, fat mass in response to exercise training. Novelty Combined exercise training in obese black South African women increased cardiorespiratory fitness and rates of fat oxidation during steady state exercise. Exercise training reduced proportional gynoid, not visceral, fat, potentially representing an ethnic/sex-specific response. Baseline substrate utilisation (resting and steady state exercise (50% peak oxygen uptake)) predicted changes in gynoid fat mass.