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1. Dietary recommendations to satisfy the energy
requirements of children and adolescents should be based on their energy expenditure
and requirements for growth. Their habitual physical activity and lifestyle
must be taken into account, as energy expenditure should be consistent with the attainment
and maintenance of long-term good health, and the performance of economically necessary
and socially desirable physical activity.
Energy for socially desirable activities is particularly important as part of the normal process of a child's development, for activities such as exploration of the surroundings, learning and behavioural adjustments to other children and adults (FAO/ WHO/UNU, 1985).
2. There is a major contrast between lifestyles of children and adolescents in rural developing societies and in developed countries. Whereas the former engage in physically-demanding obligatory or occupational activities from an early age, the latter tend to be quite sedentary (Cooper et al, 1984; Verschuur & Kemper, 1985; Atomi et al, 1986; Armstrong et al, 1990; Gortmaker et al, 1990). Discretional activities are also probably quite different in those two settings: in developing rural areas, children walk more to move around and to socialize, while those in developed countries travel in motor vehicles and spend a significant period of time sitting and watching television (Dietz and Gortmaker, 1985; Gortmaker et al, 1990).
More studies are needed in children and adolescents who live in cities of developing countries. Available evidence suggests that those in the middle and upper socioeconomic groups are relatively sedentary, with a lifestyle that resembles that of children in developed countries more than that of their rural counterparts. Habitual activities related to energy expenditure in the lower socioeconomic groups have hardly been studied.
3. Recommendations to fulfill energy requirements of children and adolescents should be made according to two or three levels of intensity of habitual physical activity, in a manner similar to that recommended for adults in the 1985 FAO/WHO/UNU Report. Provisional physical activity levels are suggested in Table 21.
4. The 1985 recommendation for 5% additional dietary energy intake to 'allow a desirable level of physical activity' among all children under 10 years of age seems unwarranted. Furthermore, scientific evidence accumulated in the last decade suggests that current FAO/WHO/UNU recommendations for dietary energy are too high for children under 5, and possibly under 7, years of age.
5. Current recommendations seem somewhat low for adolescent boys and for girls around puberty. This is more so in rural areas of the developing world, where recommendations for girls throughout adolescence and for boys and girls of school age may also be too low when expressed per unit of body weight or as multiples of BMR.
6. Healthy but stunted or slightly underweight boys and girls in developing countries seem to have a higher energy requirement per unit of body weight than their well-nourished, non-stunted counterparts. The differences in absolute terms and PAL units are less consistent. It seems reasonable to recommend for them the same total dietary energy intakes as for well-nourished, non-stunted children of the same age and sex, provided that they are encouraged and have opportunities to be physically active.
7. Dietary energy recommendations
must be accompanied by strong recommendations for physical activity compatible with
the achievement and maintenance of health, prevention of obesity and adequate social
and psychological development. The minimum amount of exercise required by children for
a healthy life has not been exactly determined. Provisional recommendations can be made,
similar to those for adults, based on Simons-Morton et al's (1988) review of
recommendations for physical activity for children: exercise involving dynamic movement of
large muscle groups for at least 20 min, three or more times a week, at an intensity that
raises and maintains heart rate at 140 or more beats per minute.
There are some contradictory and non-conclusive
results on the role of physical activity for the prevention of obesity, but as Gortmaker et
al (1990) point out, obesity seems to have a stronger relationship with inactivity
than with vigorous physical activity.
Methodological considerations
8. The use of doubly-labeled water provides, at present, the most exact quantitative measurements of TEE of free-living children and adolescents. However, financial and technical constraints limit its application in samples large enough to represent boys and girls of all ages living in a wide variety of social and geographic settings. Minute-by-minute heart rate monitoring techniques seem promising for this purpose, especially if they are validated in the field with doubly-labeled water measurements.
9. Time-motion or activity diary techniques can provide useful information to confirm or monitor the accuracy of dietary recommendations. Sampling must be adequate in size, physiological and anthropological characteristics, and appropriate factors must be applied to quantify the energy expended in the observed/recorded/timed activities. These techniques also provide an important insight on the pattern of habitual activities of children and adolescents.
10. There is a need to obtain more information on the energy cost of activities and tasks in which children and adolescents from different societies typically engage, in order to increase and improve existing databases (e.g. Torun, 1990a). Standardized procedures must be established to define those activities and tasks and to measure their energy cost.
11. Time allocation studies can help to define the appropriate level of habitual physical activity for specific (geographic, ethnic, social) groups of children and adolescents. There is, however, a need to develop standardized procedures for the collection of time allocation data in different societies across all age groups.
12. The use of multiples of BMR, or physical activity levels (PAL), is useful in physiological and practical terms to calculate the energy expenditure and estimate the energy requirements of population groups. PALs for children and adolescents with different lifestyles have been suggested in this paper.
13. It seems that a single set of mathematical equations cannot be used across all races and geographic regions to calculate the ]BMR of boys or girls of a specific age group. To avoid making important errors in the estimation of energy requirements and recommendations, this issue must be cleared. If necessary, specific sets of mathematical equations should be derived for some races or countries.
14. Dietary energy intake studies tend to overestimate energy requirements of children under 8 and to underestimate those of children over 12 years of age. Nevertheless, they may be useful to estimate requirements of a healthy, well growing population when total energy expenditure cannot be measured or calculated. However, to accept the data as representative of habitual and appropriate intake, it is necessary that it should be: (a) derived from adequate population samples; (b) validated by studies that take into account the method used for data collection, as well as the anthropological, geographic and health characteristics of the population and (c) screened and edited to exclude information that is incompatible with fundamental principles of energy physiology in population groups (e.g. exclusion of data below or above cut-off points compatible with long-term habitual eating patterns of a healthy population). Provisional cut-off points, calculated as multiples of BMR, are suggested in this paper.
Other conclusions and recommendations
15. Other specific conclusions, including recommendations for important and much needed research, are included at the end of each section in this document.