Decrease in fat oxidation following a meal in weight-reduced individuals: a possible mechanism for weight recidivism.

This study examined the effect that dietary-induced weight loss has on body composition, energy metabolism, and substrate oxidation at rest and during the 5-hour period following a meal. Twenty older (age:mean +/- SE, 61 +/- 1 years; range, 56 to 70 y) obese (body mass index > 32 kg/m2) subjects (12 women, eight men) completed an 11-week dietary restriction program in which they lost 9 +/- l kg. Fat and fat-free mass were reduced (P < .05) by 15% and 5%, respectively. Resting metabolic rate decreased by 15% (P < .05). Overall, weight loss did not alter the percentage of energy derived from fat sources (approximately 47% of energy) under resting conditions. In contrast, the percentage of calories derived from fat during the 5-hour postmeal period decreased from baseline to post-weight loss from 38% +/- 3% to 26% +/- 4% (P < .05) of total calories expended. The reduction in fat oxidation subsequent to a meal may facilitate fat storage, and may be one mechanism by which one regains weight following weight loss.