Discussion (summarized by W. Dietz)

Lucas used an average figure for diet-induced thermogenesis. The early period of infancy is the most crucial for the ability to dissipate energy, and body weight offers no clue to this capability. Therefore even early body weight may not represent the most important variable.

The decision to breast- or bottle-feed may select a variety of behavioral characteristics independent of infant feeding. Early data support the hypothesis that infants who are handled more grow faster, raising the possibility that long-term effects on growth may be a consequence of early CNS responses. On the other hand, whether a child is lean or obese, may alter the manner in which it is treated.

It appears that seriously obese women may have had an early disease experience producing undernutrition either on a behavioral or thermogenetic basis. Few data are available that support this hypothesis in humans; some do so in rats.

Some of the linkage between birthweight or early growth and mortality may be related to ethnicity. The most sensitive periods may be prenatal or the first year of life.

If diet in infancy and early childhood has any long-term effects, we need to explore underlying mechanisms. Gastrointestinal hormones may be an important factor. Lucas et al. have shown major differences between breast- and formula-fed infants which could account for differences in growth in the two groups.