Similarly, although (diet-induced-) obesity-prone rat pups cross-fostered to obesity resistant dams remained obese, they had improved insulin sensitivity as adults; in contrast, obesity resistant rat pups cross-fostered to genetically obese dams showed a diet-induced increase in adiposity, reduced insulin sensitivity and changes in hypothalamic neuropeptide expression [8]. This evidence concerns the gene INS and obesity due to melanocortin 4 receptor deficiency.