Effect of dietary macronutrients on food intake, body weight, and tail width in the marsupial S-crassicaudata

The role of dietary fat, as opposed to total energy intake, in the etiology of obesity is controversial. The aim of this study was to determine the ef fect of macronutrient content, specifically changes in dietary fat on body weight, fat stores, and food intake in S, crassicaudata, a marsupial that s tores about 25% of total body fat in its tail. Female animals were divided into three groups (n = 7-9) matched for food intake per gram of body weight . Each group of animals was fed, ad lib, an isocaloric diet (1.01 kcal/g), which contained either 10, 20, or 40% of calories from fat. Body weight, fo od intake, and tail width (an index of body fat stores) were measured daily . Over 21 days, cumulative energy intake was less (p = 0.026) in the 40% fa t group compared to the 10% fat group. Despite the differences in food inta ke, body weight in each group remained stable throughout the study, so that at day 21 there were no differences in the body weights between the three groups. In contrast, tail width increased in the animals who received the 4 0% fat diet compared to either the 10% (p = 0.016) or 20% (p = 0.001) fat i ntake groups, whereas there was no significant change in tail width in eith er of these two groups. These observations indicate that macronutrient comp osition has a role, independent of total calories in the regulation of food intake and body fat stores, specifically that dietary fat promotes adiposi ty, independent of total caloric intake. (C) 1999 Elsevier Science Inc.