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Introduction
Total daily energy expenditure (TEE)
Estimates of basal metabolic rate to calculate total energy expenditure
Time allocation to different activities
Physical activity levels of children and adolescents
Dietary energy intake
General conclusions and recommendations
References
Discussion
B Torun1, PSW Davies2, MBE Livingstone3, M Paolisso4, R Sackett5, GB Spurr6 (with contribution from MPE de Guzman7)
1 Health
and Nutrition Unit, Institute of Nutrition of Central America and
Panama, Apartado Postal 1188, Guatemala, Guatemala;
2 Infant and
Child Nutrition Group, MRC Dunn Nutrition Unit, Cambridge CB4
IXJ, UK;
3 Department of
Biological and Biomedical Science, University of Ulster,
Coleraine, Northern Ireland BT52 ISA, UK;
4 International
Center for Research on Women, Washington, DC 20036, USA;
5 Departments of
Anthropology, Memphis State University, Memphis, TN 38152, USA;
6 Department of
Physiology, Medical College of Wisconsin, Milwaukee, WI 53295,
USA;
7 Department of
Science and Technology, Food and Nutrition Research Institute,
Metro Manila 1604, Philippines
Descriptors:
energy requirements, energy expenditure, physical activity,
dietary energy, children, adolescents, time allocation
In 1981, a group of experts
was convened by FAO, WHO and UNU to evaluate the energy and
protein requirements of humans, and to make appropriate dietary
recommendations. Several key concepts related to energy were
asserted in their report (FAO/WHO/ UNU, 1985), which included the
following:
• The energy requirement is the amount of dietary energy needed to maintain health, growth, and an 'appropriate' level of physical activity.
• 'Appropriate' physical activity includes those activities that an individual must perform to survive in his/her social environment (occupational activities), and to pursue his/her physical, intellectual and social desires and wellbeing (discretionary activities). For children, this should allow the exploration of the surroundings and the interaction with other children and adults.
• Energy needs are determined by energy expenditure. Therefore, estimates of requirements should be based on measurements of energy expenditure and, for children, an additional allowance for growth.
• Energy requirements can be calculated as multiples of basal metabolic rate (BMR). In the absence of direct measurements, BMR can be estimated with mathematical equations derived from published metabolic data.
However, very little information was available on total energy expenditure (TEE) of children. Consequently, estimates of energy requirements for 1-10 year old children were based on the reported energy intakes of healthy, well nourished children, with the tacit assumption that they represented habitual intakes. These estimated requirements were derived from an extensive review of published dietary intake data on approximately 6500 children, mostly from developed countries (Ferro-Luzzi & Durnin, 1981).
Correspondence
to: Dr B Torun.
Note: Participation in the
preparation of this document does not imply that all contributors
agree with all of the conclusions and recommendations
The FAO/WHO/UNU Expert Committee was also concerned about a perceived secular trend towards sedentary lifestyles in developed countries. Therefore, it was felt prudent to increase by 5% the reported energy intakes of children between 1 and 10 years of age to accommodate a desirable level of physical activity.
After 10 years of age, estimates of energy expenditure expressed as multiples of BMR provided the basis to calculate energy requirements, rather than energy intake data. BMR for boys and girls of a given age and weight were predicted with the mathematical equations derived by Schofield (FAO/WHO/UNU, 1985; Schofield, 1985), and the additional energy expended during the day was calculated based on the assumed energy cost of activities performed by children and adolescents in developed countries. The extra allowance for growth was assumed to be 5.6 kcal (23.4 kJ) per gram of expected weight gain. This corresponded to about 3% of the daily energy requirement at one year of age, with a gradual decrease to about 1% at 15 years.
In deriving these estimates of energy requirements for children and adolescents the FAO/WHO/UNU Expert Committee acknowledged that they exceeded the dietary energy intakes reported for these ages. It was considered that the low intakes reflected an undesirably low level of physical activity, and that dietary recommendations should include enough energy to allow an increase in activity. It should be noted that the spontaneous activity of children and hence energy expenditure can be restricted by energy intake as demonstrated by studies in Guatemala (Town, 1990b).
In the years that followed the 1981 FAO/WHO/ UNU Expert Consultation, more has been learned about the energy expenditure of children and adolescents and of the way they distribute their time in activities that demand different levels of energy expenditure, largely due to the application of the doubly-labeled water method, the improved technology and validation of heart-rate monitoring techniques, and the analysis of physiological, nutritional and anthropological studies (Schürch & Scrimshaw, 1990). Additional information on food intake and on basal and resting metabolic rates have also allowed a better appraisal of the calculation and validity of energy requirements between 1 and 18 years of age.
This
document presents a critical review of that knowledge and makes
recommendations for consideration by the group of experts that
will revise the 1985 FAO/WHO/UNU report.