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Sedentary femaleb

1950 (8100 kJ)

Sedentary malec

2500 (10200kJ)

Female, moderately activeb

2200 (9200 kJ)

Male, moderately activec

3000 (12 500kJ)

Female, very activeb

2500 (10400kJ)

Male, very activec

3200 (13300kJ)

aValues are based on estimated average requirements from a report by the Committee on Medical Aspects of Food Policy (1991). Dietary reference values are for food energy and nutrients for the United Kingdom. bBased on female age 25years, body weight 60 kg. cBased on male age 25years, body weight 70 kg.

controlled by an individual, and therefore it may represent an appropriate method for altering energy balance. Physical activity is estimated to make up 5-40% of daily energy expenditure depending on the activity habits of the individual, with RMR and TEF accounting for 60-75 and 10-15%, respectively.

Aside from its direct independent effect on daily energy expenditure, evidence suggests that exercise may also alter RMR, TEF, and the energy expenditure caused by spontaneous physical activity.

Energy Expenditure during Exercise

The magnitude of energy expenditure during exercise is dependent on several factors, including the mode, intensity, and duration of exercise, as well as the body mass of the individual.

When determining the metabolic cost of weight-bearing physical activity, energy expenditure needs to be expressed in relation to body size since a small person will expend less energy performing a given activity (e.g., walking up a flight of stairs) than a larger person performing the same activity. Therefore, to calculate the energy cost of a given activity it is necessary to know the energy cost in kcal (kJ) per kilogram of body weight. The term MET (metabolic equivalent) may also be used to indicate the ratio of the rate of energy expenditure during a given activity to resting metabolic rate (RMR). An example illustrates how METs are used to quantify energy expenditure during exercise. If an individual with a body mass of 70 kg expends 70 kcal («300 kJ) per hour at rest (RMR), and walking at a speed of 5.6 km per hour requires 280 kcal («1200 kJ) per hour, the energy cost of the activity is 4 METs or four times the RMR of the individual. Since body size is a determinant of both RMR and the energy expenditure during exercise, a heavier individual will have a higher RMR but will still require four times this level of expenditure (or 4 METs) to walk at the same speed. Table 2

Table 2 Energy costs of popular physical activities

Activity

Intensity

METs

Walking

6.4 km fr1

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