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1.Nitrogen balance, weight loss and resting metabolic rate were measured in thirty-eight obese inpatients on 2. All subjects were fed on 13% protein-energy in three rneals/d for the first week. 3. In weeks 2 or 3, using a cross-over design, ten subjects were fed on 15 or 10% protein-energy as three rneals/d; fourteen subjects were fed on five or one meal/d with 13%proteinenergy; and fourteen subjects were fed on 15% protein-energy as five mealsld or 10% protein-emergy as one meal/d. 4. N loss was least on the high-protein week and frequent-meal week: the largest difference was found when these effects were combined (P < 0.001). 5. When protein-energy was held constant at 13% N loss decreased significantly (P < 0.01) between week 2 and 3, but when the proteinenergy was manipulated there was no significant N conservation in the third week.This suggests that the protein:energy value is more important than meal frequency in the preservation of lean tissue. 6. Weight loss was also least on the 'high-protein' week and 'frequent-meal' week, but this result reached significance only when the effects were combined (P < 0.05).
7.Resting metabolic rate decreased with time but was not significantly altered by the dietary regimens.8. Therefore, during the first 3 weeks at an intake of 3.4 MJ/d, a diet with a high-protein concentration, fed as frequent small meals, is associated with better preservation of lean tissue than an isoenergetic diet with lower-protein concentration fed as fewer meals. There was no evidence that meal frequency or protein concentration affect the rate of fat loss. Cohn et al. (1963) showed that if one group of rats was fed ad lib., and a similar group of rats was force-pair-fed the identical diet in two meals/d, the force-fed rats gained more fat and excreted more nitrogen than the ad lib. control group. The higher the protein concentration in the diet, the more marked was the effect of force-feeding. This observation was linked with that of Fabry et al. (1964) who noted that there was an inverse relationship between the frequency of meals and adiposity in the population of Prague, and this has been confirmed in the Tecumseh study (Metzner et al. 1977). Mahler (1972) found that students who took a large carbohydrate supplement as a single meal gained more weight than when the supplement was divided in sixteen hourly fractions, but this result may be due to the order in which the tests were done, because the gorging protocol always preceded the nibbling one. Debry et al. (1973) compared the weight loss in 119 obese subjects who were given a reducing diet as either three or seven meals daily: the mean weight loss on seven meals/d was 142 g, but on three meals it was only 78 g/d. All these publications may be taken as support for the view that isoenergetic diets taken as a small number of large meals (gorging) are more fattening than the same diet taken as a large number of small meals (nibbling).From the viewpoint of energy balance it is difficult to understand why this should be so. If the diet ...