We recently reported on an elevation of neurons expressing the main orexigenic peptide neuropeptide Y (NPY) in the arcuate hypothalamic nucleus (ARC) of neonatally hyperinsulinaemic offspring of gestational diabetic mother rats (GD) at weaning. To investigate possible consequences, the long-term outcome of those animals was examined. At adult age, GD offspring showed hyperphagia (p < 0.001), basal hyperinsulinaemia (p < 0.05) and impaired glucose tolerance (p < 0.05), and were overweight (p < 0.01). This was accompanied by an elevated number of NPY neurons (p < 0.001) and galanin neurons (p < 0.001) in the ARC in adult GD offspring under basal conditions. These findings support our hypothesis on perinatally acquired, persisting malformation and/or malprogramming of peptidergic hypothalamic neurons in the offspring of GD mothers, possibly promoting the development of overweight and diabetogenic disturbances during life.