In anticipation of the revision of the 1985 Food and Agricultural Organization/World Health Organization/United Nations University (FAO/ WHO/UNU) Expert Consultation Report on ‘Energy and Protein Requirements’, recent scientific knowledge on the principles underlying the estimation of energy requirement is reviewed.

This paper carries out a historical review of the scientific rationale adopted by previous FAO/WHO technical reports on energy requirement, discusses the concepts used in assessing basal metabolic rate (BMR), energy expenditure, physical activity level (PAL), and examines current controversial areas. Recommendations and areas of future research are presented.

The database of the BMR predictive equations developed by the 1985 FAO/WHO/UNU Expert Consultation Report on Energy and Protein Requirements needs updating and expansion, applying strict and transparent selection criteria. The existence of an ethnic/tropical factor capable of affecting BMR is not supported by the available evidence. The factorial approach for the calculation of energy requirement, as set out in the 1985 report, should be retained. The estimate should have a normative rather than a prescriptive nature, except for the allowance provided for extra physical activity for sedentary populations, and for the prevention of non-communicable chronic diseases. The estimate of energy requirement of children below the age of 10 years should be made on the basis of energy expenditure rather than energy intake. The evidence of the existence of an ethnic/tropical factor is conflicting and no plausible mechanism has as yet been put forward.

To estimate the energy requirements of infants from total energy expenditure and energy deposition during growth.

Energy requirements during infancy were estimated from total energy expenditure measured by the doubly labelled water method and energy deposition based on measured protein and fat gains.

Database on the total energy expenditure and energy deposition of infants was compiled from available studies conducted in China, Chile, Gambia, Mexico, Netherlands, UK, and USA.

Healthy, term infants.

Total energy requirements (kJ day−1) increased with age and were higher in boys than girls due to differences in weight. Energy requirements decreased from 473 kJ kg−1 per day for boys and 447 kJ kg−1 per day for girls at 1 month of age to 337 kJ kg−1 per day for boys and 341 kJ kg−1 per day for girls at 6 months of age, and thereafter tended to plateau. Energy deposition as a percentage of total energy requirements decreased from 40% at 1 month to 3% at 12 months of age. These estimates are 10–32% lower than the 1985 FAO/WHO/UNU recommendations which were based on observed energy intakes of infants.

Recommendations for the energy intake of infants should be revised based on new estimates of total energy expenditure and energy deposition.

To describe issues related to energy requirements of free living adults and discuss the importance of basal metabolic rate (BMR) and their relationships to total energy expenditure (TEE ) and physical activity level (PAL, derived as TEE/BMR) and to determine the influence of body weight, height, age and sex.

Based on a review of the literature, this paper examines the variability in BMR due to methodology, ethnicity, migration and adaptation (both metabolic and behavioural) due to changes in nutritional status. Collates and compiles data on measurements of TEE in free living healthy adults, to arrive at limits and to compare TEE of populations with different life-styles.

The constancy of BMR and its validity as a reliable predictor of TEE in adults as well as the validity of PAL as an index of TEE adjusted for BMR and thus its use to categorise the physical activity pattern and lifestyle of an individual was confirmed. The limits of human daily energy expenditure at around 1.2×BMR and 4.5×BMR based on measurements made in free living adults have been reported in the literature. A large and robust database now exists of energy expenditure measurements obtained by the doubly labelled water method in the scientific literature and the data shows that, in general, levels of energy expenditure are similar to the recommendations for energy requirements adopted by FAO/WHO/UNU (1985). The review also confirms that metabolic adaptation to energy restriction is not an important factor that needs to be considered when recommending energy requirements for adults in developing countries.

To estimate the energy requirements of pregnant and lactating women consistent with optimal pregnancy outcome and adequate milk production.

Total energy cost of pregnancy was estimated using the factorial approach from pregnancy-induced increments in basal metabolic rate measured by respiratory calorimetry or from increments in total energy expenditure measured by the doubly labelled water method, plus energy deposition attributed to protein and fat accretion during pregnancy.

Database on changes in basal metabolic rate and total energy expenditure during pregnancy, and increments in protein based on measurements of total body potassium, and fat derived from multi-compartment body composition models was compiled. Energy requirements during lactation were derived from rates of milk production, energy density of human milk, and energy mobilisation from tissues.

Healthy pregnant and lactating women.

The estimated total cost of pregnancy for women with a mean gestational weight gain of 12.0 kg, was 321 or 325 MJ, distributed as 375, 1200, 1950 kJ day-1, for the first, second and third trimesters, respectively. For exclusive breastfeeding, the energy cost of lactation was 2.62 MJ day-1 based on a mean milk production of 749 g day-1, energy density of milk of 2.8 kJ g-1, and energetic efficiency of 0.80. In well-nourished women, this may be subsidised by energy mobilisation from tissues on the order of 0.72 MJ day-1, resulting in a net increment of 1.9 MJ day-1 over non-pregnant, non-lactating energy requirements.

Recommendations for energy intake of pregnant and lactating women should be updated based on recently available data.

To summarise the literature on energy requirements and aging.

An analysis and review of published data on components of energy expenditure and total energy expenditure (TEE).

Data on basal metabolic rate (BMR) and TEE were obtained from the US Institute of Medicine of the National Academies database (all available data from studies published before 2001, collected from 20 researchers willing to provide individual subject results).

Those individuals from the database who were 20–100 years of age.

TEE and physical activity level (PAL, defined as the ratio of total to resting energy expenditure) declined progressively throughout adult life in both normal weight and overweight men and women. In normal weight individuals (defined as body mass index (BMI) 18.5–25.0 kg m-2) TEE fell by ≈150 kcal per decade, and PAL fell from an average of 1.75 in the second decade of life to 1.28 in the ninth decade. Thermic effect of feeding data from other published studies indicated no consistent change associated with aging.

Aging is associated with progressive declines in resting and TEE, which have implications for defining dietary energy requirements at different stages of adult life.

To provide a concise summary of field and laboratory methods for the measurement of dietary intake with particular reference to the assessment of energy and protein intake and to the pitfalls and difficulties that may be encountered in practice when implementing the methods both in the field and under laboratory conditions.

This background paper was prepared in response to a request to review the concepts related to measurement of body composition, to discuss laboratory and field methods of assessing body composition and to discuss the practical applications of the methods – how they might be used singly or in combination to provide data for a selected population.

The common laboratory and field methods are described and discussed, with particular attention to the assumptions involved and the applicability of the methods to the different population groups. Most measurements of body composition are made in the field, at the bedside or clinic as opposed to in the laboratory. The laboratory methods have a role to play in their own right, in research into new concepts, models and methods. However, they are particularly important in establishing the accuracy of the field methods.

Field, bedside and laboratory studies.

Children, adults, the elderly, ethnic groups.

Laboratory estimates of body compositions are best performed by multi-component methods or by 2-component methods adjusted for to the populations under investigation. There is a scarcity of data for most of the populations in the world.

Energy requirements based on body weight are an approximation since they do not take into account differences in body composition, which will better determine the true requirements. The measurement of body composition occurs in many branches of biology and medicine. It is used in the assessment of nutritional and growth status and in disease states and their treatment. Energy stores, skeletal muscle and protein content can be determined and changes monitored. In human energetics, body composition is widely used for the standardisation of other variables, such as basal metabolic rate (BMR), in the assessments of ethnic and environmental differences and of variability and adaptation to different levels of nutrition. Choosing a method is very problematic. Users want simple, inexpensive, rapid, safe accurate methods to measure body composition but speed and simplicity come at the expense of accuracy. Recommendations are made for age, sex, and in some cases, fatness and ethnic specific methods.

To facilitate the Food and Agriculture Organization/World Health Organization/United Nations University Joint (FAO/WHO/UNU) Expert Consultation on Energy and Protein Requirements which met in Rome in 1981, Schofield et al. reviewed the literature and produced predictive equations for both sexes for the following ages: 0–3, 3–10, 10–18, 18–30, 30–60 and >60 years. These formed the basis for the equations used in 1985 FAO/WHO/UNU document, Energy and Protein Requirements.

While Schofield's analysis has served a significant role in re-establishing the importance of using basal metabolic rate (BMR) to predict human energy requirements, recent workers have subsequently queried the universal validity and application of these equations. A survey of the most recent studies (1980–2000) in BMR suggests that in most cases the current FAO/WHO/UNU predictive equations overestimate BMR in many communities. The FAO/WHO/UNU equations to predict BMR were developed using a database that contained a disproportionate number – 3388 out of 7173 (47%) – of Italian subjects. The Schofield database contained relatively few subjects from the tropical region.

The objective here is to review the historical development in the measurement and application of BMR and to critically review the Schofield et al. BMR database presenting a series of new equations to predict BMR.

This division, while arbitrary, will enable readers who wish to omit the historical review of BMR to concentrate on the evolution of the new BMR equations.

BMR data collected from published and measured values.

A series of new equations (Oxford equations) have been developed using a data set of 10 552 BMR values that (1) excluded all the Italian subjects and (2) included a much larger number (4018) of people from the tropics.

In general, the Oxford equations tend to produce lower BMR values than the current FAO/WHO/UNU equations in 18–30 and 30–60 year old males and in all females over 18 years of age.

This is an opportune moment to re-examine the role and place of BMR measurements in estimating total energy requirements today. The Oxford equations' future use and application will surely depend on their ability to predict more accurately the BMR in contemporary populations.

There were two objectives: first, to review the existing data on energy costs of specified activities in the light of the recommendations made by the Joint Food and Agriculture Organization/World Health Organization/United Nations University (FAO/WHO/UNU) Expert Consultation of 1985. Second, to compile existing data on the energy costs of physical activities for an updated annexure of the current Expert Consultation on Energy and Protein Requirements.

Electronic and manual search of the literature (predominantly English) to obtain published data on the energy costs of physical activities. The majority of the data prior to 1955 were obtained using an earlier compilation of Passmore and Durnin. Energy costs were expressed as physical activity ratio (PAR); the energy cost of the activity divided by either the measured or predicted basal metabolic rate (BMR).

The compilation provides PARs for an expanded range of activities that include general personal activities, transport, domestic chores, occupational activities, sports and other recreational activities for men and women, separately, where available. The present compilation is largely in agreement with the 1985 compilation, for activities that are common to both compilations.

The present compilation has been based on the need to provide data on adults for a wide spectrum of human activity. There are, however, lacunae in the available data for many activities, between genders, across age groups and in various physiological states.

To examine the evidence as to whether the relationship between undernutrition and poor child development is causal.

Selected studies from developing countries were discussed. Observational studies were first considered then experimental studies of preventative and remedial supplementation. The type of functions affected, the presence of sensitive periods and the role of protein and energy versus that of micronutrients were reviewed.

Childhood undernutrition is generally associated with concurrent and longer term deficits in cognition, behaviour and motor skills, although the relationship is likely to be confounded by socio-economic factors. Supplementation trials have had many design problems. However, those beginning at any age from pregnancy up to 24 months have consistently had concurrent benefits suggesting a causal relationship. Supplement begun in older children had little or no effect, albeit there are too few studies to conclude with confidence. The limited evidence suggests that benefits are more likely to be sustained if supplementation begins in late pregnancy or at birth and is continued until the child is at least 24 months old.

Deficits in cognition tend to be global and there is insufficient evidence of specific deficits. There is some evidence that the first 2 years of life are most sensitive to the effects of undernutrition. Most studies have failed to separate the effects of energy and protein from those of micronutrients. One study showed that energy and/or protein affects children's development. Psychosocial stimulation has had consistent benefits on undernourished childrens' development

Public health nutrition programmes should include a component in which children who are at risk are targeted during the first 2 years of life with combined interventions involving nutrition, health care and early stimulation.

To produce prediction equations for basal metabolic rate (BMR) derived from weight and height covering the age range from birth to old age.

Cross-sectional data on BMR, sex, age, weight, height, ethnicity and measurement technique from the Oxford Brookes BMR database.

Worldwide.

Data for 13 910 men, women and children from 174 papers published between 1914 and 2001.

Absolute and proportional regression models were developed for each sex, showing a steep rise in predicted BMR with age until 15 years, more pronounced in males than females, then a gradual fall through adulthood. Predicted BMR increased by 6% and 1.4%, respectively, per standard deviation increase in weight and height. Predicted BMR in Caucasians was 4% higher than in non-Caucasians, though the effect size was sensitive to the inclusion or exclusion of data from certain influential publications. The effect of measurement technique on BMR, closed-circuit versus open-circuit, was small, near 1%.

It is possible to develop prediction equations that avoid splitting the data into arbitrary age groups. Heterogeneity between publications is greater than might be expected by chance, probably due to undocumented differences in technique.