Failure of dietary fat intake to promote fat oxidation: A factor favoring the development of obesity

Abstract

Seven young men spent three nights and 2 d in a respiration chamber where their rates of energy expenditure and substrate oxidation were continuously measured by indirect calorimetry. During the first 24 h they ingested a mixed maintenance diet containing 35% of calories as fat. An additional amount of 106 ± 6 g fat/24 h (x̄ ± SD) was added to this diet during the following 36 h. The fat supplement (987 ± 55 kcal/d) did not alter 24-h energy expenditure (2783 ± 232 vs 2820 ± 284 kcal/d) and failed to promote the use of fat as a metabolic fuel (fat oxidation 1032 ± 205 vs 1042 ± 205 kcal/d). The overall energy balance was closely correlated with the fat balance (r = 0.96, p < 0.001) but not with the carbohydrate balance (r = -0.12, NS). These data indicate that substantial imbalances between intake and oxidation are much more likely for fat than for carbohydrate.