Approximately 90 percent of the daily calorie expenditures of most people occurs as a result of the resting metabolic rate (RMR). The RMR is slightly higher than the BMR; it includes the BMR plus any additional energy expended through daily sedentary activities, such as food digestion, sitting, studying, or standing. The exercise metabolic rate (EMR) accounts for the remaining 10 percent of all daily calorie expenditures; it refers to the energy expenditure that occurs during physical exercise. For most of us, these calories come from light daily activities, such as walking, climbing stairs, and mowing the lawn. If we increase the level and intensity of physical activity to moderate or heavy, however, our EMR may be 10 to 20 times greater than typical resting metabolic rates and can contribute substantially to weight loss.
Increasing BMR, RMR, or EMR levels will help burn calories. An increase in the intensity, frequency, and duration of daily exercise levels may have significant impact on total calorie expenditure.
Physical activity makes a greater contribution to BMR when large muscle groups are used. The energy spent on physical activity is the energy used to move the body’s muscles – the muscles of the arms, back, abdomen, legs, and so on – and the extra energy used to speed up heartbeat and respiration rate. The number of calories spent depends on three factors:
1. The amount of muscle mass moved
2. The amount of weight being moved
3. The amount of time the activity takes
An activity involving both the arms and the legs burns more calories than one involving only the legs, an activity performed by a heavy person burns more calories than one performed by a lighter person, and an activity performed for 40 minutes requires twice as much energy as the same activity performed for only 20 minutes. Thus, obese persons walking for 1 mile burn more calories than slim people walking the same distance. It may also take overweight people longer to walk the mile, which means that they are burning energy for a longer time and therefore expending more overall calories than are thin walkers.
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