No abstract

Hunger may be delayed and food intake reduced under metabolic conditions that spare carbohydrate oxidation, especially during oxidation of medium-chain triacylglycerols (MCTs) or monounsaturated triacylglycerols. In 12 healthy, adult, male volunteers isolated and deprived of any time cues, we compared the effects of 4 high-carbohydrate breakfasts (1670 kJ) supplemented either with a fat substitute (Sub; 70 kJ) or with 1460 kJ fat as monounsaturated long-chain triacylglycerols (LCT-U), saturated long-chain triacylglycerols (LCT-S), or MCTs. In the first session we investigated the effects of these breakfasts on the following food intake variables: hunger ratings at repeated intervals, the time until the spontaneous request for the next 2 free-choice meals, and the amount of food consumed. In a second session with fixed lunches, we studied the effects of the same breakfasts on plasma glucose, insulin, triacylglycerol, fatty acid, and beta-hydroxybutyrate concentrations. The addition of any of the fats to the high-carbohydrate breakfasts did not alter hunger ratings, but significantly delayed the request for lunch compared with the low-fat breakfast. The free-choice lunch eaten after the MCT breakfast was also significantly smaller. Blood glucose and insulin concentrations were lower after the 3 fat breakfasts, followed by larger increases in glucose and enhanced insulin responses 30 min after the lunch. No differences were observed between the LCT-U and LCT-S conditions. We conclude that MCTs decreased food intake by a postabsorptive mechanism, although the exact effect of these lipids on carbohydrate oxidation will require further studies involving nutrient balance measurements.

CHAPELOT, DIDIER, CORINNE MARMONIER, ROBERTE AUBERT, CHLOÉ ALLÈ GRE, NICOLAS GAUSSERES, MARC FANTINO, AND JEANINE LOUIS-SYLVESTRE. Consequence of omitting or adding a meal in man on body composition, food intake, and metabolism. Obesity. 2006;14:215-227. Objective: To investigate in man the consequence on body composition and related biological and metabolic parameters of omitting or adding a meal. Research Methods and Procedures: Twenty-four young normal-weight male subjects were recruited, 12 usual fourmeal and 12 usual three-meal eaters, differing only in the consumption of an afternoon meal. They omitted or added a fourth meal during a 28-day habituation period and were asked to report their intake on three 3-day occasions. Before and after this habituation period, subjects participated in a session with a time-blinded procedure, and blood was collected continuously from lunch to the spontaneously requested dinner. Body composition, respiratory quotient, and biochemical parameters were measured in the late evening preceding each session. Results: Omitting a meal was followed by increases in fat mass (360 Ϯ 115 grams, p Ͻ 0.05), late evening leptin concentration (20.7 Ϯ 11.0%, p Ͻ 0.05), and respiratory quotient (3.7 Ϯ 1.4%, p Ͻ 0.05). Increase in the percentage of dietary fat during the habituation period (ϩ4.1 Ϯ 2.0%, p Ͻ 0.05) was correlated with fat mass (r ϭ 0.66, p Ͻ 0.05). Adding a meal had no effect, but, in both groups, the change in energy content at this fourth eating occasion was correlated with the change in adiposity. Discussion: Our results suggest that adiposity may increase when young lean male subjects switch from a four-to a three-meal pattern by removing their usual afternoon meal. This effect could be partly mediated by a change in the macronutrient composition of the diet.