Revisiting the relationship of weight and height in early childhood.

Ponderal and linear growth of children has been widely studied; however, epidemiologic evidence of a relationship between the two is inconsistent. Child undernutrition in the form of low height for age and low weight for height continues to burden the developing world. A downward shift in the distribution of height for age in the first 2 y of life is commonly observed in many developing countries and is usually summarized as the percentage stunted (height for age Z-score <-2). Similar shifts are seen in weight for height; however, weight-for-height shifts are often less extreme, perhaps because weight for height is more tightly biologically controlled. Low height for age and low weight for height in childhood share some common factors, including food insecurity, infectious diseases, and inappropriate feeding practices. Reductions in weight for height, generally seen as a short-term response to inadequate dietary intake or utilization, are thought to precede decreases in height for age; however, given an adequate diet and no further insults, catch-up linear growth can occur. Serial instances of decreased weight for height, however, are thought to limit the degree of catch-up growth attained, contributing to linear growth retardation. Additional research is needed to identify the factors associated with recovery of linear growth after a child experiences decreased weight for height. Although the direct relationship between weight for height and height for age is likely limited, each of these measurements indicates important information about the general health of children and their risk of the development of illness or dying; therefore, eliminating the downward shift of height for age and weight for height in developing countries should be prioritized as a public policy.