Obesity is often associated with decreased fat oxidation and aging is a well-recognized risk factor for cardiovascular disease. This study investigated calorimetric and morphometric parameters, as well as the glucose levels, lipid profile and cardiac energy metabolism in young and old, controls and obese rats. The animals were divided into four groups: Group I (GI): young rats fed normal diet for 75 days; Group II (GII): young rats fed hypercaloric diet (HD) for 75 days; Group III (GIII): old rats fed normal diet for 510 days; and Group IV (G IV): old rats fed HD for 510 days. The following analyses were performed: calorimetric, glucose and lipid concentrations, atherogenic index (AI), total antioxidant substances (TAS), fat depots, cardiac lipid hydroperoxide (LH) and cardiac lactate dehydrogenase (LDH), citrate synthase (CS), phosphofructokinase (PFK) and pyruvate dehydrogenase (PDH) activities. Older animals were heavier than young and the hypercaloric animals were heavier than controls. Animals from GIV had lower fat oxidation than GIII, which in turn, had higher fat oxidation than GI. Total cholesterol, LDL-C and all fat depots were higher in the GII, as compared to GI. The GIV rats had higher VLDL, retroperitoneal fat, serum lipids and cardiac glycogen levels than GII. Furthermore, GIV rats had higher fat depots, triacylglycerol, total cholesterol and VLDL than GIII. Animals from GII and -IV showed higher LH and AI than age-matched controls. Older hypercaloric rats also had higher TAS than older control rats, which also had lower LH and TAS than younger control rats. Aged animals had increased CS and LDH and decreased PFK and PDH activities. Additionally, GIV rats exhibited an increase in PDH activity, compared to GIII. We conclude that the consumption of HD coupled with aging leads to impaired basal and cardiac metabolism.