. 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 ...

The purpose of the work was to assess endogenous nitrogen output in dogs of widely contrasting mature body size and genotype. Fecal and urinary nitrogen excretion was measured during 14-day metabolic periods in 25 adult dogs of body-weight range 2.8-51.0 kg fed a protein-free, semipurified diet. Endogenous nitrogen excretion was assumed from day 8 after introduction of the protein-free diet and was measured during the final 7 days of each period. Mean (+/- SEM) endogenous urinary nitrogen (EUN), metabolic fecal nitrogen (MFN), and total endogenous nitrogen (TEN) outputs were 210 +/- 9, 63 +/- 3 and 273 +/- 9 mg/kg 0.75 per day. There were no significant effect of either sex or body weight on the magnitude of EUN, MFN or TEN outputs, however, EUN output was positively and significantly (P less than 0.02) correlated (r = 0.50) with percentage body-weight loss during the metabolic period. The mean values obtained for endogenous nitrogen output in adult dogs agreed closely with previous estimates in the literature for dogs exhibiting a narrower range (8.3-16.7 kg) of mature body weight.

Digestible energy (DE) needs for body weight maintenance (BWM) of six adult Beagles and six domestic cats were comparatively assessed by using data from thirteen 14-day and nine 21-day consecutive apparent digestibility trials, respectively. In each trial the Beagles and cats were given different commercial foods, and feces were quantitatively collected excluding the first 7 days. The relationship between mean daily body weight change (delta BW) per trial and DE intake was examined by regression analysis of data for individual animals. Pooled mean (n = 6) data from 223 Beagle and 143 cats digestibility trials were analyzed by the same method. Significant (P less than 0.05) linear regressions between delta BW and DE intake were obtained (R2 = 0.43-0.93) for all individual Beagles, five of six cats and pooled mean data for both Beagles and cats. Mean (range) daily DE needs for BWM of six individual Beagles were 70 (63-78), 140 (127-146) and 173 (156-187) kcal for data scaled to kilograms, kilograms0.75 and kilograms0.67 BW, respectively. Respective values for six individual cats were 76 (56-89), 104 (86-114) and 114 (95-122) kcal. Analysis of group mean data for Beagles and cats generated daily DE costs for BWM of 76 and 66 kcal/kg, respectively, equivalent to 148 and 95 kcal/kg0.75. Thus adult cats had significantly (P less than 0.001) lower energy costs of BWM than Beagles when scaled to metabolic BW (kilograms0.75 or kilograms0.67), but not on an absolute BW basis.

Of the factors known to influence metabolic rate it is those with the most marked effect, such as exercise, food intake and temperature extremes, which have attracted the most interest and therefore been the most thoroughly investigated. While researchers have long agreed that emotional disturbance of a subject during a measurement of metabolic rate is likely to lead to errors in the measurement, the evidence for such an effect has been largely anecdotal and there has been very little systematic research attempted. The most widely available method of measuring metabolic rate is that of indirect calorimetry, that is, by estimating oxygen consumption, and the errors inherent in the method, coupled with the difficulty in achieving a consistent baseline, make the study of small increases in metabolic rate, such as would be expected to result from anxiety, very difficult.

1. Total heat loss was measured by 24 h direct calorimetry in five obese and five lean women who were maintained throughout the study on a diet supplying 3·3 MJ/d. Each subject was measured five times to assess the effect of temperature, exercise and food on energy expenditure. Within each weight group a Latin-square design was used to balance sequence effects on the thermogenic responses to temperature, exercise and food.2. Compared with the control day, on which no thermogenic stimulus was given, the increase in 24 h heat production by the lean and obese women caused by 30 min exercise on a bicycle ergometer against a load of 20 N was 10·1 and 10·3 W for obese and lean groups respectively. There was no evidence in either group of a measurable long-term increase in metabolism which would increase the energy cost of the exercise above that predicted from indirect calorimetry during the exercise.3. The increase in heat production associated with ingesting an extra 4·4 MJ (obese group) or 4·0 MJ (lean group) was 3·4 and 3·0 W respectively. This response was similar to that predicted from indirect calorimetry for a few hours after the meal.4. The obese and lean groups differed in metabolic response to calorimetry at the upper or lower limits of the thermal comfort zone, which was determined individually for each subject. The difference from control values in the obese group was an increase of 3·8 W on the ‘warm’ run, and a decrease of 2·0 W on the ‘cool’ run. Among subjects the change was an increase of 0·4 W on the ‘warm’ run, and an increase of 4·8 W on the ‘cool’ run. The differences between the groups did not achieve statistical significance. The lower and upper temperature limits were similar in the two groups: 23·2–26·4° for the obese group, and 23·3–26·2° for the lean group.5. The most striking difference between lean and obese subjects in the present study was the much higher resting metabolic rate, and total energy expenditure, of the obese group. During the control run the obese group had a mean energy expenditure of 96·1 W, compared with 61·7 W in the lean group. There was no overlap: the lowest energy expenditure for an obese subject was 81·4 W and the highest for a lean subject was 76·1 W. In comparison to this large difference in baseline the magnitude of the thermogenic responses was small.6. Under the conditions of this study there was nothing to support the view that a failure of thermogenic response is an important factor in the causation of human obesity. To support that view it would be necessary to show differences in thermogenesis in lean and obese subjects which were at least an order of magnitude greater than those which we have observed.