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Physical activity levels of children and adolescents

The occupational and habitual activities of adults are classified as light, moderate and heavy, and taken into account to calculate and recommend dietary energy intakes. The data presented in this document supports the suggestion that the same approach must be applied to children from 5 years of age onwards.

To do so, estimates must be made of the 24-hour PAL of children and adolescents with different lifestyles. This is usually associated with their geographic habitat (urban or rural, industrialized or developing country) and socioeconomic conditions.

An analysis of the PALs calculated in this review for children studied with doubly-labeled water, heart rate monitoring, time-motion/diary techniques and time allocation estimates allows making practical suggestions. Table 19 summarizes those calculations for industrialized countries and cities in developing countries, calculated as weighted means for the total number of boys or girls included in all studies with a specific technique. Studies with mean PAL < 1.40 for children over 5 years old were excluded, as well as those with PAL > 1.90 at all ages, as those figures are very unlikely to represent the habitual activity level of children in cities and industrialized countries. The mean PALS of normal and stunted children calculated from heart rate monitoring methods were combined as they were derived from otherwise healthy children, and in most cases they agreed within 4%.

There is hardly any information of TEE of children and adolescents living in rural developing countries. Therefore, we only estimated their PAL from time allocation data, as described in the preceding section and shown in Tables 15, 16 and 18.

The estimates of PALs from studies on time-motion/ diary records and time allocation data involve a series of assumptions on the energy cost of activities and tasks to calculate TEE. Thus, it seems more reasonable to use the data derived from doubly-labeled water and heart rate monitoring studies to suggest PALs to estimate the energy expenditure and requirements of children and adolescents from different populations. Such PALs, based on the data in Table 19, are shown in Table 20. Assuming that those levels of physical activity correspond to children and adolescents who are neither extremely sedentary nor active and are consuming dietary energy ad libitum, we suggest that they are equivalent to a moderate PAL.

The mean coefficient of variance (CV) of the studies with doubly-labeled water and heart rate monitoring in boys and girls 1-5, 6-13 and >14 years old shown in Tables 3 and 5 is 6%. We calculated the PAL of light and heavy lifestyles by subtracting or adding twice the CV (i.e. 12%) from the moderate PAL of children and adolescents over 5 years old (Table 20). It is unlikely that infants and preschoolers have a heavy physical lifestyle. Consequently, for that age group it is suggested that the mean of the PALs shown in Table 19 (measured by DLW or HR) be applied to a 'light' lifestyle, and the additional 12% (twice the mean CV) be applied to a 'moderate' PAL.

Table 20 Physical activity levels suggested to estimate total daily energy expenditure from the mean basal metabolic rate of children and adolescents

Table 21 Data from Table 20 rounded to the closest 0.05 PAL units

To facilitate remembering those PAL factors, it is further suggested to round them to the closest 0.05 PAL units, as shown in Table 21.

As more information on TEE and BMR of boys and girls with different lifestyles becomes available and the questions related to the mathematical equations to estimate BMR are cleared, the PALs shown in Table 21 may be modified. In the meantime, their use is suggested as a first approximation to estimate energy requirements in population groups where actual data is unavailable. Table 22 shows those estimates for boys and girls with median weights-for-age corresponding to the NCHS standards. Figure 7 compares them with measurements using doubly labeled water and heart rate monitoring, expressed as kcal/kg/day.

Table 22 Estimates of total daily energy expenditure from the physical activity levels suggested in Table 21 and basal metabolic rates calculated with Schofield's equations

^a Median weight for age, NCHS/WHO.
^b PAL factors shown in Table 21.
^c Assume values similar to moderate physical activity in children 1-3 years old.

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