Fat mass localization affects lipid metabolism differently at rest and during exercise in overweight and normal-weight subjects. The aim of this study was to investigate the impact of a low vs high ratio of abdominal to lower-body fat mass (index of adipose tissue distribution) on the exercise intensity (Lipox_max) that elicits the maximum lipid oxidation rate in normal-weight women.

Twenty-one normal-weight women (22.0±0.6 years, 22.3±0.1kg.m⁻²) were separated into two groups of either a low or high abdominal to lower-body fat mass ratio [L-A/LB (n=11) or H-A/LB (n=10), respectively]. Lipox_max and maximum lipid oxidation rate (MLOR) were determined during a submaximum incremental exercise test. Abdominal and lower-body fat mass were determined from DXA scans.

The two groups did not differ in aerobic fitness, total fat mass, or total and localized fat-free mass. Lipox_max and MLOR were significantly lower in H-A/LB vs L-A/LB women (43±3% VO_2max vs 54±4% VO_2max, and 4.8±0.6mgmin⁻¹kg FFM⁻¹ vs 8.4±0.9mgmin⁻¹kg FFM⁻¹, respectively; P<0.001). Total and abdominal fat mass measurements were negatively associated with Lipox_max (r=–0.57 and r=–0.64, respectively; P<0.01) and MLOR [r=–0.63 (P<0.01) and r=–0.76 (P<0.001), respectively].

These findings indicate that, in normal-weight women, a predominantly abdominal fat mass distribution compared with a predominantly peripheral fat mass distribution is associated with a lower capacity to maximize lipid oxidation during exercise, as evidenced by their lower Lipoxmax and MLOR.