Effects of obesity, food restriction and pregnancy on fetal and maternal weight and on body composition in rats.

The effects of obesity and food restriction on fetal and maternal body weight and on maternal body composition were determined in pregnant and nonpregnant rats. Obesity was induced by several weeks of ad libitum feeding of a varied diet of retail food products which continued until experimental day 5 (gestational age in pregnant groups). From day 5 all groups were fed a standard diet. Ad libitum-fed obese pregnant rats gained less weight during pregnancy than non-obese rats. All rats which were 60% food restricted lost body weight. Weight loss in obese rats was due to loss of body fat whereas non-obese rats lost lean tissue as well. Obese pregnant rats ended the food restriction period 62 g heavier than non-obese restricted pregnant rats and had the same carcass weight and composition as ad libitum fed non-obese nonpregnant rats. Fetal and placental weight was reduced 25 percent by food restriction in obese as well as non-obese groups. These results indicate that during food restriction the fetal rat cannot parasitize maternal nutrient stores to prevent growth retardation, even if the mother is obese.