It has been demonstrated that a high-protein diet in preterm born infants during the first weeks of life may enable a growth rate equal to that seen in utero and may also result in a better long-term neurodevelopmental outcome. This diet may limit immediate postnatal growth retardation and may hence lower the risk of increased fat deposition after birth leading to the metabolic syndrome in later life. Insulin-like growth factor I (IGF I) has proven to play an important role in early postnatal growth of preterm infants, but also seems to have a persisting influence on body composition in childhood. Furthermore, increased IGF I concentrations in preterm infants have been associated with improved neurodevelopmental outcome. This review will elaborate on the role of dietary proteins and IGF I on growth, body composition, and neurodevelopment of preterm infants. Possible causal pathways will be explored and areas for future research will be proposed.