Characterization of diet-induced obese rats that develop persistent obesity after 6 months of high-fat followed by 1 month of low-fat diet.

A subset of Sprague-Dawley rats developed persistent obesity when maintained on a high-fat diet for 6 months followed by a low-fat diet for 1 month, while another subset from the same cohort of rats remained lean on the same diet regimens. The diet-induced obese (DIO) rats had higher energy intake than expenditure, while diet-resistant (DR) rats maintained energy balance. DIO rats also had an increased respiratory quotient and higher levels of plasma leptin, insulin and cholesterol. In the hypothalamic areas, DIO rats had elevated NPY and AGRP mRNA, but not MCH mRNA. Our data suggest that the increase in hypothalamic expression of NPY and AGRP may contribute to the development of persistent obesity in DIO rats.