Obese mothers’ offspring develop obesity and metabolic alterations in adulthood. Poor postnatal dietary patterns also contribute to obesity and its comorbidities. We aimed to determine whether in obese mothers’ offspring an adverse postnatal environment, such as high-fat diet (HFD) consumption (second hit) exacerbates body fat accumulation, metabolic alterations and adipocyte size distribution. Female Wistar rats ate chow (C-5%-fat) or HFD (MO-25%-fat) from weaning until the end of lactation. Male offspring were weaned on either control (C/C and MO/C, maternal diet/offspring diet) or HFD (C/HF and MO/HF) diet. At 110 postnatal days offspring were euthanized. Fat depots were excised to estimate adiposity index (AI). Serum glucose, triglyceride, leptin, insulin, insulin resistance index (HOMA-IR), corticosterone, and dehydroepiandrosterone (DHEA) were determined. Adipocyte size distribution was evaluated in retroperitoneal fat. Body weight was similar in C/C and MO/C but higher in C/HF and MO/HF. AI, leptin, insulin, and HOMA-IR were higher in MO/C and C/HF vs C/C but lower than MO/HF. Glucose increased in MO/HF vs MO/C. C/HF and MO/C had higher triglyceride and corticosterone than C/C, but lower corticosterone than MO/HF. DHEA and the DHEA/corticosterone ratio were lower in C/HF and MO/C vs C/C, but higher than MO/HF. Small adipocyte proportion decreased while large adipocyte proportions increased in MO/C and C/HF vs C/C and exacerbated in MO/HF vs C/HF. Postnatal consumption of a HFD by the offspring of obese mothers exacerbates body fat accumulation as well as the decrease of small and the increase of large adipocytes, that lead to larger metabolic abnormalities.