The formula for the extrapolation is

EAR_child = EAR_adult (F),

where F = (Weight_child/Weight_adult)^0.75 (1 + growth factor). Reference weights from Table 1-1 are used. If the EAR differs for men and women, the reference weight used for adults in the equation differs by gender; otherwise, the average for men and women is used unless the value for women is derived from data on men. The approximate proportional increase in protein requirements for growth (FAO/WHO/UNA, 1985) is used as an estimate of the growth factor as shown in Table 3-1. If only an AI has been set for adults, it is substituted for the EAR in the above formula, and an AI is calculated; no RDA is set.

To account for variability in requirements because of growth rates and other factors, a 10 percent coefficient of variation (CV) for the requirement is assumed unless data are available to support another value, as described in Chapter 1.

This adjustment, the metabolic weight ratio method, involves metabolic scaling but does not adjust for growth because it is based on a value for a growing infant. To extrapolate from the AI for infants ages 0 through 6 months to an AI for infants ages 7 through 12 months, the following formula is used:

AI_{7–12 mo} = AI_{0–6 mo} (F),

where F = (Weight_{7–12 mo}/Weight_{0–6 mo})^0.75.