Human beings must obtain enough energy from the food they eat if they are to be healthy and active. Diets may, of course, provide sufficient calories and yet be grossly unsatisfactory in other respects, particularly in terms of protein content. Inequalities among countries are much more pronounced for proteins than for calories; protein shortages are both more frequent and relatively greater, and such shortages are more serious in their consequences. However, a serious calorie deficiency may deteriorate the protein status of a person, because in that case protein may be utilized for energy, even in people whose diets are already low in protein.
Recently it was estimated that the national per capita calorie and protein supply fell below the recommended minimum in at least half of the developing countries. However, national averages conceal wide disparities among population groups within countries.