Several pre-and post-natal factors are suggested to impact the risk development of cardiovascular diseases and the risk of obesity later in life. 1,2 Early signs of disease are apparent already in childhood, in which a low or high birth weight, high maternal pre-pregnancy body mass index (BMI), and a rapid infant weight gain are associated with obesity and cardiometabolic risk factors. 3-6 Generally, these factors are either linked to undernutrition or overnutrition of the developing fetus or infant. Fewer studies have examined the possibility that preand post-natal factors may also influence subsequent health behaviors, for example, participation in physical activity. Most previous studies have examined the association between birth weight and subsequent physical activity. Although two systematic reviews 7,8 concluded that birth weight is unlikely to impact subsequent physical activity, studies generally only examined the linear association. There are probably different mechanisms linking developmental undernutrition (assessed eg, by a low birth weight) and developmental overnutrition (assessed eg, by a