Energy expenditure concerns calories burned versus calories consumed. Imbalances between the two determine weight loss, gain or maintenance. Bodies that store too much energy become overweight. One component of your expenditure is basal metabolic rate -- the energy you burn when inactive. The other two components are activity thermogenesis, which are the calories burned during activity, and the thermic effect of foods, which concerns calories used to digest foods you eat.
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Percentages of Components
If you were to make a pie chart illustrating total energy expenditure, or TEE, the largest wedge would be basal metabolic rate, or BMR, or the closely related resting metabolic rate. Both reflect energy expended while inactive.The Food and Agriculture Organization of the United Nations says BMR can range from 45 percent for people with a vigorous lifestyle to 70 percent for those who are sedentary. The Colorado Clinical and Translational Sciences Institute, a health and education consortium, says activity thermogenesis -- the burning of calories while moving -- is the second largest wedge of TEE. This is energy expended during sports, exercise and nonexercise activity thermogenesis, or NEAT, which encompasses activities of daily living including fidgeting. The remainder of TEE comes from the thermic effect of food, the energy used during digestion, absorption and storage of nutrients.
Basal Metabolic Rate
Basal metabolic rate has to be measured upon waking in a darkened room after 8 hours of sleep and 12 hours of fasting. It is more common to use the measure called resting metabolic rate, or RMR, when calculating total energy expenditure, because RMR doesn't require sleeping overnight in a testing facility. It can be calculated while you sit for a period of time; hwever, if you don't know your BMR or RMR, you can still estimate daily calories needed for weight loss or maintenance by adding up caloric estimates for all your activities in an average 24-hour period.
Estimates of activity thermogenesis are based on energy use during vigorous activities as well as NEAT activities throughout the day. Certified strength and conditioning specialist Jacob Wilson, who works with body builders, notes that NEAT activities, such as standing and pacing during work, consume more calories than sitting. James Krieger of Weightology Weekly says a decrease in NEAT is a bigger culprit in weight gain than a decreasing metabolic rate. He notes that as people become more efficient at daily tasks, they streamline movements and reduce energy expenditure. Both Krieger and Wilson say adults can compensate by purposely increasing their nonexercise activities, such as climbing stairs instead of using elevators. Wilson says even chewing gum increases activity thermogenesis.
The body uses lots of energy when it processes certain unrefined foods, including lean meats, vegetables and whole grains. For some foods, including broccoli, celery, lemon water and salsa, this process may burn more calories than they contain. In effect, they become zero-calorie foods that help you stay full and healthy while losing or maintaining weight.