Basal metabolic rate (BMR), and the closely related resting metabolic rate (RMR), is the amount of energy expended while at rest in a neutrally temperate environment, in the post-absorptive state (meaning that the digestive system is inactive, which requires about twelve hours of fasting in humans). The release of energy in this state is sufficient only for the functioning of the vital organs, the heart, lungs and kidneys and the rest of the nervous system, intestine, liver, lungs, sex organs, muscles and skin. BMR decreases with age and with the loss of lean body mass. Increasing muscle mass increases BMR. Aerobic fitness level, a product of cardiovascular exercise, while previously thought to have effect on BMR, has been shown in the 1990s not to correlate with BMR, when fat-free body mass was adjusted for.

New research has however come to light wh(ich suggests anaerobic exercise does increase resting energy consumption. Illness, previously consumed food and beverages, environmental temperature, and stress levels can affect one’s overall energy expenditure as well as one’s BMR.

English BMR Formula Women: BMR = 655 + ( 4.35 x weight in pounds ) + ( 4.7 x height in inches ) – ( 4.7 x age in years ) English BMR Formula Men: BMR = 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) – ( 6.8 x age in year ) The

BMR formula uses the variables of height, weight, age and gender to calculate the Basal Metabolic Rate (BMR). This is more accurate than calculating calorie needs based on body weight alone. The only factor it omits is lean body mass and thus the ratio of muscle-to-fat a body has. Remember, leaner bodies need more calories than less leaner ones. Therefore, this equation will be very accurate in all but the very muscular (will underestimate calorie needs) and the very fat (will over-estimate calorie needs).

You use energy no matter what you’re doing, even when sleeping. The BMR Calculator will calculate your Basal Metabolic Rate (BMR); the number of calories you’d burn if you stayed in bed all day.

If you’ve noticed that every year, it becomes harder to eat whatever you want and stay slim, you’ve also learnt that your BMR decreases as you age. Likewise, depriving yourself of food in hopes of losing weight also decreases your BMR, a foil to your intentions. However, a regular routine of cardiovascular exercise can increase your BMR, improving your health and fitness when your body’s ability to burn energy gradually slows down.
BMR is measured under very restrictive circumstances when a person is awake. An accurate BMR measurement requires that the person’s sympathetic nervous system not be stimulated, such a condition whose prerequisite is that of complete rest. A more common and closely related measurement, used under less strict conditions, is resting metabolic rate (RMR).

BMR and RMR are measured by gas analysis through either direct or indirect calorimetry, though a rough estimation can be acquired through an equation using age, sex, height, and weight. Studies of energy metabolism using both methods provide convincing evidence for the validity of the respiratory quotient (R.Q.), which measures the inherent composition and utilization of carbohydrates, fats and proteins as they are converted to energy substrate units that can be used by the body as energy. Studies conducted by Spennewyn in 1990 found strong correlations between lean mass and metabolism based on indirect calorimetry measurements. Spennewyn discovered that lean tissue in men and women required approximately 16 calories per pound per day. Thus, once a lean mass was known it could be multiplied by 16 to reveal daily caloric needs based on the activity level of the individual. This method has been used in many health club environments to determine daily caloric needs.