Adults

The nutrition and health of adults is particularly important, because it is this age group that is primarily responsible for the economic support of the rest of the society. In non-industrialized societies, where agricultural work is the dominant economic activity, physical capacity and endurance are critical to the ability of adults to sustain the socio-economic and cultural integrity of their community. Variability in adult weight is recognized as being linked with variation in adult height, which in turn reflects a number of environmental factors active throughout much of childhood. The term "underweight" in adult assessment was therefore applied to individuals of low body weight relative to height, generally expressed in terms of BMI.

TABLE 2. Estimated median ages for maturational events in the NCHS/WHO reference population

Maturational stage		Median age(yr)
Boys
	genitalia stage 3	12.4
	peak height velocity	13.5
	adult voice	14.5
Girls
	breast stage 2	10.6
	peak height velocity	11.7
	menarche	12.8

Source: ref. 7.

After its review of current evidence, the Committee concluded that there is no obvious need for reference data for BMI in adults, and it would be best to rely on pragmatically derived cut-off values of BMI. This recommendation is based on the evidence that the prevalence of thinness and overweight varies widely from country to country, and there are no indications that different populations with the same distributions of BMI have similar relative and attributable risks of morbidity and mortality associated with different degrees of overweight and thinness. BMI values vary widely, depending on the populations assessed (fig. 4). Also, as the proportion of the population with low BMI decreases, there is an almost symmetrical increase in the proportion with BMIs above 25. This indicates a tendency for a population-wide shift as socio-economic conditions improve, with overweight replacing thinness.

FIG. 4. BMI distribution of various adult populations of both sexes worldwide.

Source: ref. 7

If sufficient data are collected in the future, however, reference data or even standards could be developed. To understand the distribution of BMI values in a healthy population and collect appropriate data for generating a reference set of weights, it is important that data are derived from populations with no nutritional problems (underfeeding and overfeeding), in whom children's growth is unimpaired by recurrent infections, and the young individuals in the population are largely free of disease and do not smoke.

Data for the potential development of reference data should include at least weight and height, age, sex, and race. Socio-economic status and smoking habits may be necessary to adjust for these influences. Information would also need to be included that would permit the exclusion of persons who have abnormal weights relative to healthy, well-nourished, non-pregnant individuals, for example, the presence of disease, dieting, and weight history.