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5.4 Energy requirements and dietary energy recommendations5.4.1 Calculation of energy requirements Energy requirements were calculated from the factorial estimates of PAL described in the preceding sections. They were converted into energy units (i.e. joules and calories) by multiplying the PAL value by the BMR. In order to express requirements as energy units per kilogram of body weight, they were divided by the weight used in the equations to predict BMR. The following example to calculate the average energy requirement of a female population 20 to 30 years of age with a moderately active lifestyle and a mean body weight of 55 kg illustrates these calculations: BMR (calculated with the predictive equation in Table 5.2): 5.45 MJ/day (1 302 kcal/day). The variation in requirements around the mid-point of the PAL ranges in each lifestyle category in Table 5.3 is between ± 8 percent and ± 10 percent (e.g. PAL for moderately active lifestyle = 1.70 to 1.99 = 1.85 ± 8 percent). However, there are individuals with BMR or PAL values at the extremes of a normal distribution around the population mean. Consequently, within each lifestyle category there are people whose individual energy requirement is beyond the limits shown in Table 5.3. This reiterates the fact that the energy requirements and dietary energy recommendations in this report are to be applied to population groups and not to individuals. Requirements of a specific individual must be based on that person’s actual TEE or BMR, or on estimates that take into account the individual’s habitual physical activity and lifestyle characteristics. Tables 5.4 to 5.9 show the average energy requirements of populations with various levels of habitual physical activity and various mean body weights. Requirements for groups with other weights and/or mean PAL can be calculated easily, as in the following example for men 20 to 25 years of age with an average weight of 68 kg and an estimated PAL of 1.80:
Another option for calculations is:
5.4.2 Recommendation for daily energy intake Dietary energy intake of a healthy, well-nourished population should allow for maintaining an adequate BMI at the population’s usual level of energy expenditure. At the individual level, a normal range of 18.5 to 24.9 kg/m2 BMI is generally accepted (WHO 1995 and 2000). At a population level, a median BMI of 21.0 was recently suggested by the joint WHO/FAO Expert Consultation on Diet, Nutrition and the Prevention of Chronic Diseases (WHO/FAO, 2002). As BMI is a function of weight and height, heights corresponding to a BMI of 18.5, 21.0 and 24.9 were included in Tables 5.4 to 5.9 for each mean weight shown in the first column of each table. This facilitates recommendations for dietary energy intakes aimed at maintaining those values or range of BMI. For example, in the case of a male population 18 to 30 years old with an average height of 1.70 m and an activity lifestyle with a mean PAL of 1.75, the recommended energy intake would be around 11.7 MJ/day or 195 kJ/kg/day, which corresponds to the average requirement of men with a height of 1.69 m and a BMI of 21.0 who have a PAL of 1.75 × BMR (Table 5.4). In the same example, a range of approximately 11.1 to 12.8 MJ/day or 185 to 200 kJ/kg/day would allow the maintenance of a BMI between 18.5 and 24.9 kg/m2. These figures were obtained from the PAL column of 1.75 × BMR in Table 5.4, between the lowest row with height ³ 1.70 m in the column of 18.5 BMI (in this example, the second row with a height of 1.72 m) and the highest row with height £ 1.70 m in the column of 24.9 BMI (in this example, the fifth row with a height of 1.68 m). TABLE 5.4
TABLE 5.5
TABLE 5.6
TABLE 5.7
TABLE 5.8
TABLE 5.9
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