Dietary and 24-h fat oxidation in Asians and whites who differ in body composition.

BACKGROUND: With the same BMI, age, and sex, Asians were reported to have a higher body fat percentage than whites. OBJECTIVE: This study aimed to determine the difference in body composition and its effect on dietary and 24-h fat oxidation between Asians and whites when they were fed a diet that contained 30% of energy as fat. DESIGN: Seventeen Asians (8 men) were matched with 17 whites (8 men) for BMI, age, and sex. Physical activity was measured for 7 d with an accelerometer. During the last 3 d of the activity measurement, subjects were given a diet to maintain energy balances. Energy expenditure and substrate use were measured for 24 h in a respiration chamber. Dietary fat oxidation was determined from the percentage recovery of deuterium in the urine after a breakfast meal that contained deuterated palmitic acid. Body composition was calculated with a 3-compartment model from body mass, body volume (hydrodensitometry), and total body water (deuterium dilution). RESULTS: Asians had 5% higher body fat than that of whites (28.1 +/- 7.3% compared with 23.0 +/- 6.9%, respectively; P = 0.03). The fat-free mass index tended to be lower in Asians than in whites (16.3 +/- 1.6 compared with 17.0 +/- 1.7 kg/m(2), respectively; P = 0.07). Dietary fat oxidation as a percentage of fat consumed was 11.7 +/- 3.6% compared with 10.8 +/- 4.5% (P = 0.50) for Asians and whites, respectively. In Asians and whites, the 24-h fat oxidation as a percentage of total energy expenditure was 17.7 +/- 6.9% compared with 19.2 +/- 5.1% (P = 0.63), respectively; carbohydrate oxidation was 68.0 +/- 6.8% compared with 66.1 +/- 5.1% (P = 0.51), respectively; and protein oxidation was 14.3 +/- 2.2 compared with 14.7 +/- 1.6% (P = 0.61), respectively. CONCLUSION: Dietary and 24-h fat oxidation were not different between Asians and whites despite differences in body composition. This study was registered in the public trial registry at www.ccmo.nl as NL31217.068.10.