Growth measurements in Sprague-Dawley rats fed diets of very low fat concentration

Young (70 g) male Sprague-Dawley rats were fed one of four diets for 28 d to determine the effects of replacing dietary fat with a noncaloric substitute. Fat contributed 17% of energy in a control diet and 36% in a high fat diet. A fat substitute was used to produce two low fat diets in which essential fatty acid was the only source of lipid. One low fat diet (low fat 1) was similar in texture to the control diet. The other low fat diet (low fat 2) was comparable to the high fat diet. Digestible energy was 92-95% of gross dietary energy in all diets. There was no effect of diet composition on energy intake of the rats. At the end of the study, animals given low fat diets weighed approximately 20 g more than those fed control or high fat diets, due to increased lean body mass. Diet had no significant effect on body fat content, gastrocnemius muscle weight or femur length. This study indicates that increasing the protein:energy ratio of the diet by replacing nonessential fat with a fat substitute may promote deposition of lean tissue rather than fat in growing animals.