Influence of Dietary Lipid and Meal Pattern on Body Composition and Lipogenesis in Adult Rats

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Abstract
An experimental model in which previously semistarved adult rats underwent rapid rates of lipogenesis served to 1) determine the influence of varied dietary and feeding regimens on body composition, 2) compare total fat deposition in a 10 day refeeding period with rates of lipogenesis, and 3) justify the use of amount of epididymal fat as an indicator of total body fat. Rats were depleted by feeding a diet devoid of protein and fat. They were refed for 10 days with diets differing in amount (0% to 20% by weight) and degree of saturation of fat (safflower oil or beef tallow) as well as in protein concentration (4% or 17% of calories). Vitamin supplements furnished essential fatty acids. Subgroups had either unlimited access to food (ad libitum) or were fed 8 out of 24 hours daily (meal-fed). High-fat versus high-carbohydrate diets increased efficiency of utilization of food energy. Rats fed the higher compared with the lower protein diet had the same energy consumption, but used energy more efficiently for growth. Meal-fed rats consumed 80% to 90% of food of ad libitum control, but food efficiency was increased with meal feeding after the first three days of the refeeding regimen. High- compared with low-fat regimens increased body fat deposition only, whereas increased dietary protein resulted in weight increases from water and fat-free solids only. The low-fat, high-carbohydrate regimen elevated rates of lipogenesis as assessed by incorporation of 3H-acetate into epididymal and hepatic lipids. Deposition of epididymal lipids was highly correlated with increased total carcass lipid after refeeding.