Understanding Human Calorie Needs: IAEA Supports FAO and WHO

Energy requirements reflect what an individual needs to maintain all bodily functions, including growth and development, depending on life stage as well as activity for long-term health, and are essential for evaluating how well food supplies can meet the nutritional demands of a population. These requirements vary in relation to a person’s age, gender, physiological status (e.g., pregnancy), level of physical activity, basal metabolic rate (BMR) (the amount of energy needed for basic life functions such as breathing and keeping the body temperature) and environment, to name a few factors. For certain groups, they encompass additional energy costs such as optimal growth in the case of children; tissue development in pregnant women; and milk production in lactating mothers. Estimating accurate energy requirements can consequently entail complex calculations and challenges – especially when attempting to do so for specific sub-populations around the globe. 

As early as the 1950s, the FAO and WHO collaborated with global nutrition specialists to assess energy requirements and, in turn, derive these estimates. Their most recent exercise in October 2001 notably developed key recommendations for specific groups.  It also maintained the use of international calculations first developed in 1985 (Schofield’s equations) to estimate BMR based on a person’s gender, age, weight and physical activity level. However, in the decades that have since elapsed, the field has seen a growing body of scientific evidence which challenges the adequacy and accuracy of some aspects of those equations for universal use.  

Discussing FAO’s seminal 2004 report on the topic, the meeting’s 15 nutrition and energy metabolism experts noted a number of developments affecting BMR: the dramatic increase in global obesity; documented variations in metabolically active tissues across different populations; and trends — specifically declines — in the amount of energy needed for essential bodily functions. They also identified several key data gaps, especially those concerning energy requirements of underrepresented populations in low- and middle-income countries (LMICs); people over 90; and pregnant and lactating women. Experts formulated a roadmap which outlined next steps to update estimates of energy requirement while suggesting areas for future research. 

“A correct estimate of energy needs at different ages is needed to plan for actions to prevent and manage different forms of malnutrition. The update may help us reconsider the design of population programmes in LMICs,” said Francesco Branca, Director of WHO’s Department of Nutrition and Food Safety.