Dietary fat oxidation as a function of body fat.

BACKGROUND It is hypothesized that low dietary fat oxidation makes subjects prone to weight gain. OBJECTIVE The aim of the study was to determine dietary fat oxidation in normal, overweight, and obese subjects. DESIGN The subjects were 38 women and 18 men with a mean (+/-SD) age of 30+/-12 y and a body mass index (in kg/m2) of 25+/-4 (range: 18-39). Dietary fat oxidation was measured with deuterated palmitic acid, given simultaneously with breakfast, while the subjects were fed under controlled conditions in a respiration chamber. Body composition was measured by hydrodensitometry and deuterium dilution. RESULTS Dietary fat oxidation, measured over 12 h after breakfast, ranged from 4% to 28% with a mean (+/-SD) of 16+/-6%. Dietary fat oxidation was negatively related to percentage body fat, and lean subjects had the highest and obese subjects the lowest values (r=-0.65, P<0.001). CONCLUSION The observed reduction in dietary fat oxidation in subjects with a higher percentage body fat may play a role in human obesity.