Maternal obesity is a risk factor for subsequent fasting hypoglycemia in human infants after birth. To investigate further this problem, we employed an animal model of obesity to study neonatal extrauterine metabolic adaptations in pups of obese and lean rats. Female Sprague-Dawley rats were fed a 'cafeteria diet' to induce obesity prior to and during pregnancy. Prior to mating, the cafeteria fed rats were significantly heavier (449 v. 345 g, P less than 0.001) than the controls. Furthermore, weight gain during pregnancy and weight at term were also significantly greater in the obese rats even though they consumed less food during pregnancy. Pup weights and the number of pups per litter were similar between the two groups. Pups born to obese mothers demonstrated hypoglycemia after being fasted for 150 and 180 min when compared with control pups. Hepatic glycogen stores were increased in the fetus of pups born to obese mothers. Glycogen content in pups born to obese mothers declined minimally after birth and remained greater than hepatic glycogen values in control pups throughout the study. In addition to increased fetal storage of glycogen, fetal hepatic triglyceride content was augmented in pups of obese rats. These triglyceride stores declined and were mobilized during fasting after birth. In contrast, hepatic triglyceride content increased after birth among control rats. These results suggest that maternal obesity results in augmented fetal hepatic tissue stores of both glycogen and triglycerides. Hypoglycemia among pups of excessively obese mothers may be due to attenuated mobilization of hepatic glycogen.(ABSTRACT TRUNCATED AT 250 WORDS)