The Influence of a Hypercaloric Diet on Gross Body and Adipose Tissue Composition in the Rat

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Abstract
The total fat content of the epididymal fat depot of the rat is a function of the number of fat cells (using DNA content as the index of cell number) in that tissue. The capacity for generation of these new cells is retained for at least the first 34 weeks of life. Although the average body weight attained by rats fed a high-fat diet for 62 weeks was 37% greater than that of rats fed a standard pellet diet, the total amounts of ash, protein, and water were substantially the same for both groups; the difference in weight being essentially accounted for by the difference in fat content. Rats fed a high-fat diet, having an average weight 23% greater than that of rats fed a standard laboratory pellet diet, were capable of reverting not only to the average weight of rats fed the pellet diet but also to the same body composition, when transferred from the high-fat to the pellet diet 31 weeks after weaning (34 weeks of age, or approximately ⅓ the total life expectancy). Basic differences appear to be retained, however, in that the animal formerly fed the high-fat diet had the ability to show a weight increase 40% greater than the rat fed pellets since weaning when both groups were fed the high-fat diet 62 weeks after weaning. The data suggest that the greater weight gain may be related to a greater number of adipose tissue cells in the rats that had once been obese.