One’s basal metabolism is the energy necessary to carry on all involuntary vital processes while the body is at rest. These processes are respiration, circulation, regulation of body temperature, and cell activity and maintenance. The rate at which energy is needed only for body maintenance is called the basal metabolism rate (BMR). The BMR may be referred to as the resting energy expenditure (REE).
Medical tests can determine one’s BMR (or REE). When such a test is given, the body is at rest and performing only the essential, involuntary functions. Voluntary activity is not measured in a BMR test. Factors that affect one’s BMR are lean body mass, body size, sex, age, heredity, physical condition, and
climate. Lean body mass is muscle as opposed to fat tissue. Because there is more metabolic activity in muscle tissue than in fat or bone tissue, muscle tissue requires more calories than does fat or bone tissue. People with large body frames require more calories than do people with small frames because the former have more body mass to maintain and move than do those with small frames.
Men usually require more energy than women. They tend to be larger and to have more lean body mass than women do.
Children require more calories per pound of body weight than adults because they are growing. As people age, the lean body mass declines, and the basal metabolic rate declines accordingly. Heredity is also a determining factor.
One’s BMR may resemble one’s parents’, just as one’s appearance may. One’s physical condition also affects the BMR. For example, women require more calories during pregnancy and lactation than at other times. The basal meta bolic rate increases during fever and decreases during periods of starvation or
severely reduced calorie intake. People living and working in extremely cold or warm climates require more calories to maintain normal body temperature than they would in a more temperate climate.
Thermic Effect of Food
The body requires energy to process food (digestion, absorption, transportation, metabolism, and storage); this requirement represents 10% of daily energy (calorie) intake. Multiply BMR by 0.10 and add to the BMR (REE) before an activity factor is calculated.
