Effects of preweaning and postweaning feed restriction on the development of polygenic obese mice.

Polygenic obese (M16) and control (ICR) mice were raised in litters of 8 (N8) or preweaning restricted in litters of 14 (N14). Mice were fed either ad libitum or postweaning restricted by automatic feeders from 4 to 10 weeks of age. All mice were fed ad libitum from 10 to 16 weeks. Preweaning restriction (N14) resulted in mice at 4 weeks with smaller body weights, fat percent, subcutaneous fat depot and adipocyte diameter than N8 mice. Most of the effects of preweaning restriction were overcome by 10 weeks. Obese mice, at 10 and 16 weeks, were heavier and had higher fat percent and larger fat depots with more and larger adipocytes than control mice. Postweaning restriction resulted in mice at 10 weeks with smaller body weight but greater fat percent, especially in the control line. Postweaning restriction of obese mice resulted in a higher percent of fat at 16 weeks. The change in eating pattern, stress or other factors associated with postweaning restriction, as imposed in this study, resulted in an altered metabolism that distributed a greater proportion of energy to fat storage than in the ad libitum fed mice. Ultimate body size and adipose tissue characteristics were determined primarily by genotype, whereas most effects of nutritional restriction were temporary.