Metabolic syndrome is a clustering of many insulin resistance-associated cardiovascular risk factors such as hypertension, hypertriglyceridaemia, low high-density lipoprotein (HDL) cholesterol, abnormal glucose metabolism and hyperinsulinaemia. Furthermore, it is known that obesity is the most common clinical state characterized by insulin resistance. Central adiposity, in particular, has been shown to be the most distinctive feature of this syndrome. Some studies have also suggested that obesity per se would be necessary for the expression of metabolic defects associated with centrally distributed fat. It has been presented that undernutrition in utero might 'programme' blood pressure, insulin resistance, blood coagulation and cholesterol metabolism and would thus have a role in the aetiology of cardiovascular disease and type 2 diabetes in adult life. Some studies have also found associations between low birthweight and metabolic syndrome in adulthood. However, criticism on this hypothesis of fetal programming has recently been presented. It has been suggested that the origins of adulthood risk of cardiovascular disease and type 2 diabetes can be related to somatic growth as a child, not necessarily to intrauterine growth. In westernized countries, the relative proportion of underweight newborn children is decreasing, and thus considering entire populations low birthweight has lost its theoretical role in the aetiology of type 2 diabetes and cardiovascular disease. On the other hand, as obesity is known to be increasing in the industrialized countries among all age groups, the association between weight gain in childhood and metabolic syndrome in adulthood is more than noteworthy. Instead of undernutrition during pregnancy, sedentary lifestyle and lack of physical exercise pose a new threat. This results in an increased occurrence of overweight in childhood, which may be the first sign of insulin resistance and future metabolic syndrome.