Increased plasma levels of glucose-dependent insulinotropic polypeptide are associated with decreased postprandial energy expenditure after modern Japanese meals.

PURPOSE: The nutritional changes that have accompanied the modernization of Japanese dietary patterns have led to significant increases in the number of people who are overweight or obese. This study aimed to clarify the effects of these nutritional changes on postprandial energy expenditure and the release of metabolism-regulating hormones. METHODS: The total daily energy content (20 % breakfast, 40 % lunch, and 40 % dinner) and macronutrient composition (carbohydrate/fat/protein) was 8807.3 kJ and 364.3:30.1:66.4 (g) for the traditional test diet and 9217.6 kJ and 331.7:66.1:76.9 (g) for the modern test diet. In experiment 1, nine healthy Japanese men participated in a crossover study during which they ingested a test diet comprising three meals; postprandial blood parameters were measured after each meal. In experiment 2, another ten men participated in a crossover study during which they ingested 2 meals, after which metabolic responses and blood variables were evaluated. RESULTS: The modern diet induced greater blood levels of glucose-dependent insulinotropic polypeptide (GIP) and ghrelin than did the traditional diet. The expected increase in postprandial energy expenditure (∆REE) tended to be dampened after the modern compared with the traditional diet. GIP was inversely correlated with ∆REE after lunch, and ghrelin was positively associated with ∆REE. CONCLUSION: Both GIP and ghrelin are robust indicators of postprandial energy expenditure. The nutritional changes accompanying the modernization of Japanese dietary patterns may increase the levels of the anabolic intestinal hormone GIP, which is associated with ∆REE, in the Japanese population. The contribution of an increased ghrelin concentration to the decreased ∆REE after the modern diet warrants further investigation.

Effects of a single and short-term ingestion of diacylglycerol on fat oxidation in rats.

This study examines the effect of diacylglycerol (DAG) oil consisting mainly of 1,3-species on fat oxidation as a possible mechanism for anti-obesity. We examined the following: (1) the long-term (23-week) effects of a DAG oil diet on the development of obesity; (2) the effect of a single ingestion of DAG oil on fat oxidation; and, (3) the short-term (2-week) effect of a DAG oil diet on fat metabolism in rats. Rats fed a DAG oil diet accumulated significantly less body fat compared to rats fed a triacylglycerol (TAG) oil diet, each oil possesses a similar fatty acid composition. More( 14)C-CO(2) was expired and less( 14)C-radioactivity was incorporated into visceral fat after administration of a tracer emulsion containing 1,3-[oleoyl-1-(14)C] diolein compared to [carboxyl-(14)C] triolein. Indirect calorimetry showed respiratory quotients were significantly lower in the DAG oil diet group than in the TAG oil diet group. More( 14)C-CO(2) was expired and less (14)C-radioactivity was incorporated into visceral fat in the DAG oil diet group than in the TAG oil diet group after a single intragastric administration of [carboxyl-(14)C] triolein. These results suggest the following. (1) DAG oil has an inhibitory effect on diet-induced fat accumulation. (2) 1,3-DAG, a major component of DAG oil, is more susceptible to oxidation. (3) A short-term ingestion of DAG oil increases fat utilization at the whole body level and results in increased oxidation of dietary fat. The stimulated fat oxidation might be one explanation for the anti-obesity effect of long-term DAG oil ingestion.