Twenty-Four Hour Total and Dietary Fat Oxidation in Lean, Obese and Reduced-Obese Adults with and without a Bout of Exercise: e94181

• Published in: PloS one Vol. 9; no. 4
• Main Authors: Bergouignan, Audrey, Kealey, Elizabeth H, Schmidt, Stacy L, Jackman, Matthew R, Bessesen, Daniel H
• Format: Journal Article
• Language: English
• Published: 01.04.2014
• ISSN: 1932-6203
• DOI: 10.1371/journal.pone.0094181

Background It has been hypothesized that obese and reduced-obese individuals have decreased oxidative capacity, which contributes to weight gain and regain. Recent data have challenged this concept. Objective To determine (1) whether total and dietary fat oxidation are decreased in obese and reduced-obese adults compared to lean but increase in response to an acute exercise bout and (2) whether regular physical activity attenuates these metabolic alterations. Design We measured 24-hr total (whole-room calorimetry) and dietary fat (14C-oleate) oxidation in Sedentary Lean (BM delta = 21.5 plus or minus 1.6; n = 10), Sedentary Obese (BM delta = 33.6 plus or minus 2.5; n = 9), Sedentary Reduced-Obese (RED-SED; BM delta = 26.9 plus or minus 3.7; n = 7) and in Physically Active Reduced-Obese (RED-EX; BM delta = 27.3 plus or minus 2.8; n = 12) men and women with or without an acute exercise bout where energy expended during exercise was not replaced. Results Although Red-SED and Red-EX had a similar level of fatness, aerobic capacity and metabolic profiles were better in Red-EX only compared to Obese subjects. No significant between-group differences were seen in 24-hr respiratory quotient (RQ, Lean: 0.831 plus or minus 0.044, Obese: 0.852 plus or minus 0.023, Red-SED: 0.864 plus or minus 0.037, Red-EX: 0.842 plus or minus 0.039), total and dietary fat oxidation. A single bout of exercise increased total (+27.8%, p<0.0001) and dietary (+6.6%, p = 0.048) fat oxidation across groups. Although exercise did not impact RQ during the day, it decreased RQ during sleep (p = 0.01) in all groups. Red-EX oxidized more fat overnight than Red-SED subjects under both resting (p = 0.036) and negative energy balance (p = 0.003) conditions, even after adjustment for fat-free mass. Conclusion Obese and reduced-obese individuals oxidize as much fat as lean both under eucaloric and negative energy balance conditions, which does not support the hypothesis of reduced oxidative capacity in these groups. Reduced-obese individuals who exercise regularly have markers of metabolic health similar to those seen in lean adults. Both the acute and chronic effects of exercise were primarily observed at night suggesting an important role of sleep in the regulation of lipid metabolism.