Adipose cellularity and body composition in polygenic obese mice as influenced by preweaning nutrition.

Male mice from a line selected for rapid postweaning growth (M16) and an unselected control (ICR) were reared from birth to 3 weeks either in litters of eight (N8) or 14 (N14). Body weight gain and feed intake of M16 mice were greater than ICR. These high rates of gain and feed intake also were extended to an older age in M16 (10 weeks) than in ICR (6 weeks). The M16 line exceeded the ICR line and N8 mice exceeded N14 for fat, lean, ash, and live body weights at 4, 6, 10, 16, and 30 weeks of age. Fat percentage was greater in N8 than N14 for both ICR and M16. The adipose cellularity of the epididymal fat pads of M16 indicated a hypertrophic-hyperplastic form of obesity at 10, 16, and 30 weeks. Within each line, the N14 mice had fewer and slightly smaller fat cells than N8. However, M16-N14 mice still had considerably more and larger fat cells than ICR-N8. Restriction of energy intake from birth to 3 weeks reduced subsequent feed intake and degree of obesity. After 4 weeks, the genetic effect exerted a greater influence on the development of obesity than the preweaning nutritional regimen.