The influence of dietary fat on fat metabolism and body fat deposition in meal-feeding and nibbling rats.

1. An experiment was done with rats (body-weight 160 g) to study the effects on fat metabolism and body composition of low (10 g/kg)- or high (140 g/kg)- fat diets fed as one meal for one 4 h period/d (meal-feeders) or as six spaced meals/d (nibblers). The daily energy intake/unit metabolic body-weight (body-weight 0.73) was the same for all four groups, and this level of intake was about 80% of that consumed by rats allowed unrestricted access to the low-fat diet. The experimental period was 76 d. 2. Rats given the high-fat diet deposited more body fat/d and, as a result, grew faster and were energetically more efficient than rats given the low-fat diet depressed de novo lipogenesis from glucose in epididymal and perirenal fat pads, whose fatty acid composition resembled that of the diet. 3. For both diets meal-feeders had greater stomach plus small intestine weights than nibblers and had higher plasma free fatty acid levels, when they were killed 15 h after their last meal. 4. Meal-feeders given the low-fat diet had the greatest rate of lipogenesis for fat pads. 5. Meal-feeders given the high-fat deposited less of the main dietary fatty acids in their fat pads. 6. There was no evidence that meal-feeders eating a high-fat diet adapt their metabolism completely that they become more efficient utlizers than those nibbling this diet. Meal-feeders eating the low-fat diet became no fatter than nibblers of this diet, possibly because they were eating less than their daily ad lib. intake.