Refeeding in fasted rats: dietary self-selection according to metabolic status

We investigated the influence of the metabolic status rats have reached during a fast on their selection of protein, fat and carbohydrate when allowed to refeed after fasting for different lengths of time. They were refed either while essentially relying on lipid fuels (group 1), or while in the further stage when there is a rise in protein breakdown (group 2). In contrast to previous studies in which rats could not select macronutrients, there was no transitory anorexia during refeeding. Macronutrient selection as well as food and energy intake on the first day of refeeding were the same for both groups, total food intake being significantly larger than prior to the fast. However, there was thereafter a distinct pattern of diet selection: while fat intake progressively decreased in group 1, it increased until the fifth day in rats of groups 2. These rats, moreover, exhibited a further rise in protein intake. The data are discussed in relation to the optimization of the restoration of body fuel reserves according to the metabolic status reached at the end of a long fast.