Meal-induced thermogenesis and obesity: Is a fat meal a risk factor for fat gain in children?

Diet composition, in particular fat intake, has been suggested to be a risk factor for obesity in humans. Several mechanisms may contribute to explain the impact of fat intake on fat gain. One factor may be the low thermogene sis induced by a mixed meal rich in fat. In a group of 11 girls (10.1 +/- 0 .3 yr), 6 obese (body mass index, 25.6 +/- 0.6 kg/m(2)), and 5 nonobese (bo dy mass index, 19 +/- 1.6 kg/m(2)), we tested the hypothesis that a mixed m eal rich in fat can elicit energy saving compared with an isocaloric and is oproteic meal rich in carbohydrate. The postabsorptive resting energy expen diture and the thermic effect of a meal (TEM) after a low fat (LF; 20% fat, 68% carbohydrate, and 12% protein) or an isocaloric (2500 kJ or 600 Cal) a nd isoproteic high fat (HF; 48% fat, 40% carbohydrate, and 12% protein) mea l were measured by indirect calorimetry. Each girl repeated the test with a different, randomly assigned menu (HF or LF) 1 week after the first test. TEM, expressed as a percentage of energy intake was significantly higher af ter a LF meal than after a HF meal (6.5 +/- 0.7% vs. 4.3 +/- 0.4%; P < 0.01 ). The postprandial respiratory quotient (RQ) was significantly higher afte r a LF meal than after a HF meal (0.86 +/- 0.013 vs. 0.83 +/- 0.014; P < 0. 001). The HF low carbohydrate meal induced a significantly lower increase i n carbohydrate oxidation than the LF meal (20.3 +/- 6.2 vs. 61.3 +/- 7.8 mg /min; P < 0.001). On the contrary, fat oxidation was significantly higher a fter a HF meal than after a LF meal (-1.3 +/- 2.4 vs. -15.1 +/- 3.6 mg/min; P < 0.01). However, the postprandial fat storage was 8-fold higher after a HF meal than after a LF meal (17.2 +/- 1.7 vs. 1.9 +/- 1.8 g; P < 0.001). These results suggest that a high fat meal is able to induce lower thermoge nesis and a higher positive fat balance than an isocaloric and isoproteic l ow fat meal. Therefore, diet composition per se must be taken into account among the various risk factors that induce obesity in children.