How Many Total Calories Per Day Are Required to Maintain Basal Function?
A calorie is a measure of energy. Your basal metabolic rate, which is commonly referred to as your metabolism, is the energy you need to burn every day in order to maintain vital bodily functions while your body is at rest. A typical human body uses about 60 to 70 percent of its daily caloric burn doing this type of "work," which includes your heartbeat, respiration, and body temperature maintenance. The rate at which your metabolism burns calories is influenced by factors such as age, weight, height, and gender, among other things.
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BMR for Children
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The basal metabolic rate goes up when cells are dividing at a rapid pace, such as when children are growing. Using the BMR calculator at ShapeFit.com, the number of calories required for basic functioning for a girl, age 9, who weighs 65 lbs. and is 4 feet tall is about 1,115. The number of calories required for a boy of the same age, height and weight is 1,018. The heavier, taller, or more active the child, the more calories are required to maintain weight.
BMR for Men
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A typical male body is made up of more muscle fiber than a typical female body. Muscle fiber requires more calories to maintain, therefore the BMR is usually higher for men. Again, the larger and more active the man, the more calories he needs to maintain his current weight. The BMR calculator at ShapeFit.com tallies the number of calories required for a 6-foot-tall male, 180 lbs. at age 25 at about 1,929. As people age, their caloric requirements diminish, so a man of the same height and weight at 35 only requires 1,861 calories to maintain normal bodily functions. By the time he reaches 70, he only needs 1,623 calories daily to maintain his weight of 180 lbs.
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BMR for Women
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Women generally have a lower metabolism than men because male bodies are made up of more lean muscle, which requires more calories to maintain. The taller, heavier, or more active a woman is, the more calories she requires to maintain basic functioning. The BMR calculator at ShapeFit.com shows a woman who is 5-feet 4-inches tall, 120 lbs. and 25 years old needs approximately 1,352 calories per day to maintain her weight. At 35, she only requires 1,305 per day, and by age 70, she would only need 1,141 calories per day. If that same woman weighed 145, the top of the range for healthy weight for her height, she would need 1,461 per day at 25, 1,414 at 35, and only 1,250 at age 70.
BMR and Weight Loss
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To lose one pound of fat, a person must burn 3,500 more calories than are consumed. In order to do that, one could decrease the amount of calories taken in or use up 3,500 more calories worth of energy. That would mean that for a 120 lb., 25 year-old, 5-foot-4 woman to lose a pound a week, she would need to reduce her daily caloric intake to just over 880 calories a day or increase her caloric expenditure by 3,500 calories per week. That is equivalent to jogging just over nine hours per week.
While cutting calories may seem like the best alternative, the Journal of the American Medical Association says that reducing caloric intake too much reduces insulin levels, which slows your metabolism, making weight loss even more difficult. For most people, the most effective way to lose weight is to add more muscle to the body and increase the daily amount of physical activity rather than attempt a drastic reduction in calories.
Calculate Your BMR
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You can find a link to an online BMR calculator in the Resources section, or you can calculate it yourself. For women, add 655 + ( 4.35 x weight in pounds) + ( 4.7 x height in inches), then subtract (4.7 x age in years) to find your BMR. For men, add 66 + (6.23 x weight in pounds) + (12.7 x height in inches), then subtract (6.8 x age in years).
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