A method of continuously reducing the circulating level of insulin like growth factor 1 (IGF-1) in the first few months of the life of an infant comprises administering to the 5 infant a nutritional composition comprising proteins in an amount such that the composition contains less than 2.25 g of protein per 100 kcal. As IGF-1 is known to be a key control point in nutritional regulation of growth, this may offer a method of reducing the risk of developing obesity in later life.