Negative Factors That Influence BMR

Basal metabolic rate, or BMR, refers to the amount of energy, or number of calories, the body needs to function at its lowest possible level. BMR amounts to the rate at which you burn energy when performing no activity at all; sleeping or lying still on a couch on an empty stomach are two examples. Any activity, from eating to walking to running, raises BMR. The higher your BMR, the more calories you have to consume to maintain your weight. Factors that lower BMR make it harder to lose or maintain weight.

Aging

• As the body ages, BMR slows down naturally. This is a normal part of the aging process and cannot be reversed. Its effects can be counteracted through exercise, which raises BMR. The older you become, the more you have to exercise to stay even. Since the tendency is to exercise less as you age, this negative factor has a real impact on BMR.

Starvation Diet

• Restricting calories drastically lowers BMR. The body uses BMR to regulate metabolism. Fewer calories means less energy. A lower metabolism requires less energy to maintain essential bodily functions. With continued caloric restrictions, the body enters starvation mode; the body is conserving calories for survival. This explains why dieters hit plateaus and cannot lose any more weight. Their BMR adjusts, so either calorie intake must be lowered or exercise increased.

Sex

• Being female is a negative factor for BMR. Men have a higher BMR than women. This helps explain why men seem to be able to lose weight faster and more easily than women. The formulas for BMR for men and women differ. One reason for the difference is muscle mass -- men tend to have more muscle than women, and muscle burns more calories than fat does, even during resting or sleeping. Weight loss programs promote weight training for just this reason.

Lack of Exercise

• Calculation of BMR requires use of the basic formula plus a multiplier that depends on how much you exercise, according to WebMD. For example, if you are sedentary, you multiply the basic formula by 1.2. Compare that with the multiplier of 1.9 for someone who performs very hard exercise or sports and has a physically demanding job or works out hard twice a week. Failure to exercise is thus a significant negative factor in the BMR calculation.