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basal metabolic rate

Basal metabolic rate (BMR) is the number of calories metabolized at rest during 24 hours and is the key to effective weight management. For a typical subject, BMR accounts for more than ninety percent of total daily expenditure - more than ninety percent of calories are burned while the subject is at rest.

The basal metabolic rate is determined by lean body weight (or fat-free mass) since only lean weight metabolizes. The formula is a simple one - the larger a subject's lean body weight, the greater the rate of caloric expenditure.

The equation used by the analyzer to predict BMR, based upon Grande and Keys (1), is as follows:

    BMR (calories/day) = 14.15 * Lean Body Weight (lb)

Converted to metric, the equation is as follows:

    BMR (calories/day) = 31.2 * Lean Body Weight (kg)

While caloric expenditure is elevated during exercise and occupational activity, the main benefit of exercise is the maintenance of lean body weight. More lean weight means greater caloric consumption all day long, even when the subject is asleep!

Dieting alone may cause a reduction in lean body weight, and can actually reduce the body's ability to burn calories. The holy grail of weight management is to maintain or increase lean weight. This is not always possible during periods of weight loss. So the goal is to minimize reduction of lean body weight. A typical subject will experience a loss of 0.45 pounds of lean weight and 0.55 pounds of fat body weight for each pound of weight loss while dieting without maintenance exercise.

Reference:
1Grande F, Keys A. Body weight, body composition, and calorie status. In R. S. Goodhart and M. E. Shils, eds. Modern nutrition in health and disease, 27, 1980. Philadelphia: Lea & Febiger.
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