The molecular mechanisms by which early nutrition alters body size permanently are not fully understood at the moment. But the growth hormone/IGF axis and programming of appetite control have been implicated as key mediators. Attenuated growth rates in early post-natal life provide a significant protection against metabolic disease and extend health-and lifespan [45, 51, 54, 55, 56] . Many genetic mutations of the growth hormone/IGF axis result in both, small body size and an increased life-and health-span. Increased lifespan and increased resistance to metabolic disease is also observed in mice nursed by dams on a low protein diet [45] . This suggests that permanent changes in body size induced by altered protein supply during lactation are accompanied by an improvement in metabolic health. In humans formula feeding has been associated with both, a more rapid increase in body weight during lactation [57] and an increased susceptibility to metabolic disorders [46, 58, 59] .