Obesity has been known in detrimental impact on cardiovascular structure and function. We investigated the effect of obesity induced by early life overfeeding on cardiac changes at postnatal 28 days. Rat pup litters were adjusted to either 3 or 10 pups per mother (overnurition and control, respectively) from day 1 to days 28 of life. At day 28 of life, we measured blood pressure, blood glucose levels, ejection fraction (EF) of echocardiography, and cardiac molecular change by western blotting. The weight gain of overfeeding group was significantly increased on days 4 and between days 10 and 28 after birth but heart weight per body weight ratio was not significantly different at day 28. Blood glucose levels, blood pressure, and EF were not changed. In the obesity group, the expressions of renin, angiotensin II type (AT) 2 receptor, matrix metalloproteinase-9 (MMP-9), tissue inhibitor of metalloproteinase-1 (TIMP-1), and plasminogen activator inhibitor-1 (PAI-1) were increased; however, osteopontin(OPN) expression was decreased (P < 0.05). The protein expressions of AT 1 receptor, monocyte chemotactic protein-1, tumor necrosis factor-慣 were not changed. These results show that obesity caused by overfeeding even in early life influences the renin-angiotensin system without changes of EF and blood pressure. Obesity also influences MMP-9, TIMP-1, OPN & PAI-1 expressions, which may deteriorate cardiac matrix protein turnover of early life. This study suggests that obesity during early life potentially changes on early molecular remodeling of the cardiovascular system.