Man’s Demand for Energy

Abstract

It is important to distinguish between energy demand and energy requirement if only because the two are seldom equal. Indeed the last symposium in this series, which was devoted to the subject of ‘Diet of Man: Needs and Wants’ (Yudkin, 1978), stressed the importance of economic status, culture, taste and nutritional knowledge as determinants of food consumption. Of these economic status is by far the most important, and the average energy intake in rich countries is considerably more than in poor countries. Figure 1 shows the relationship between energy intake expressed in terms of requirements and the gross national product (GNP) for 123 countries: the correlation coefficient is 0775 which indicates that 60% of the variation of energy intake can be accounted for by economic status. The rich countries consume more than their requirements and many poor countries consume less. Intake is equal to requirement in very few countries, i.e. demand seldom equals need.