The following terms and abbreviations are relevant to this paper. These are consistent with the definitions used in other related WHO and FAO documents (FAO 2001, 2002; James and Schofield 1990; WHO 1985, 1995).
Basal metabolic rate (BMR): The minimal rate of energy expenditure compatible with life. It is measured in the supine position under standard conditions of rest, fasting, immobility, thermoneutrality, and mental relaxation. Depending on its use, the rate is usually expressed per minute, per hour or per 24 h.
Body mass index (BMI): The indicator of weight adequacy in relation to height of older children, adolescents, and adults. It is calculated as weight (in kilograms) divided by height (in meters) squared. The acceptable range for adults is 18.5–24.9, and for children, it varies with age.
Doubly labeled water (DLW) technique: A method used to measure the average total energy expenditure of free-living individuals over several days (usually 10–14), based on the disappearance of a dose of water enriched with the stable isotopes 2H and 18O.
Energy requirement (ER): The amount of food energy needed to balance energy expenditure in order to maintain body size, body composition, and a level of necessary and desirable physical activity and to allow optimal growth and development of children, deposition of tissues during pregnancy, and secretion of milk during lactation, consistent with long-term good health. For healthy, well-nourished adults, it is equivalent to total energy expenditure. There are additional energy needs to support growth in children and in women during pregnancy and for milk production during lactation.
Heart rate monitoring (HRM): A method to measure the daily energy expenditure of free-living individuals, based on the relationship of heart rate and oxygen consumption and on minute-by-minute monitoring of heart rate.
Total energy expenditure (TEE): The energy spent, on average, in a 24-h period by an individual or a group of individuals. By definition, it reflects the average amount of energy spent in a typical day, but it is not the exact amount of energy spent each and every day.
Physical activity level (PAL): TEE for 24 h expressed as a multiple of BMR and calculated as TEE/BMR for 24 h. In adult men and non-pregnant, non-lactating women, BMR times PAL is equal to TEE or the daily energy requirement.
Physical activity ratio (PAR): The energy cost of an activity per unit of time (usually a minute or an hour) expressed as a multiple of BMR. It is calculated as energy spent in an activity/BMR, for the selected time unit.
Conversion Factors: 1 J (J) is the amount of mechanical energy required to displace a mass of 1 kg through a distance of 1 m with an acceleration of 1 m per second (1 J = 1 kg × 1 m2 × 1 s−2). Multiples of 1 000 (kilojoules, kJ) or 1 million (megajoules, MJ) are used in human nutrition. The conversion factors between joules and calories are: 1 kcal = 4.184 kJ, or conversely, 1 kJ = 0.239 kcal.
Energy equivalents: 1 g protein = 5.65 kcal; 1 g fat = 9.25 kcal.