Postprandial macronutrient oxidation in girls

Nutrition Research Newsletter, Oct, 2004

In Italy, the prevalence of obesity is high; one of the highest in Europe. Most believe that the sharp increase in the prevalence of obesity in recent years is more likely explained by the nutritional and lifestyle habits of populations in industrialized nations than genetics. With this in mind, one of the most logical risk factors of obesity is diet composition. Another factor that may potentially play a role is one's pattern of food intake. A high-energy intake at the evening meal has been associated with obesity in children. No studies have yet explored the effects of dinner composition on the postprandial nutrient balance and spontaneous food intake at breakfast in prepubertal overweight and obese children. Therefore, a recent study evaluated the relationship between meal composition at dinner and energy and nutrient oxidation overnight and at breakfast, in a group of girls with different levels of overweight.

Ten prepubertal white girls were recruited for this study. The postabsorptive and postprandial energy expenditure after a low-fat (LF; 20% fat, 68% carbohydrate and 12% protein) and an isocaloric and isoproteic high-fat (HF; 50% fat, 38% carbohydrate, 12% protein) meal were measured by indirect calorimetry. Height, weight and body composition through total body DXA were assessed in postabsorptive conditions.

Fat oxidation was not significantly different after the two different meals (LF and HF). The girls oxidized 1.8 times more fat than that ingested with the LF meal vs. 0.3 times more fat than that ingested with the HF meal. Carbohydrate oxidation was significantly higher after the LF than the HF meal. There was a relationship between fat mass and the postprandial fat and carbohydrate oxidation rate. Specifically, fat oxidation increased with the degree of adiposity after both the LF and HF meals. On the contrary, carbohydrate oxidation decreased with increasing fat mass after the LF meal but did not change after the HF meal. At breakfast, the girls spontaneously ingested a similar amount of calories and macronutrient proportions independently of their having eaten an isocaloric HF or LF dinner.

In conclusion, the results suggest that a high fat intake at dinner does not stimulate subsequent fat oxidation. Additionally, overnight endogenous fat oxidation was much lower after a high fat, low carbohydrate dinner than after an isocaloric, isoproteic low-fat dinner. As a result, short-term fat balance was compromised if the dinner consumed too high a percentage of fat.

Claudio Maffeis, Yves Schutz, Lorenza Chini, et al., Effects of dinner composition on postprandial macronutrient oxidation in prepubertal girls, Obesity Research 12(7): 1128-1135 (July 2004) [Address correspondence to Claudio Maffeis, Department of Pediatrics, University of Verona, Polyclinic G.B. Rossi, Piazza L.A. Scuro 6, 34134 Verona, Italy. E-mail: Claudio.maffeis@univr.it]