BMR - Basal Metabolic Rate

Measuring a Healthy Lifestyle
Measuring a Healthy Metabolism. Jamie Grill/Getty Images

Basal Metabolic Rate (BMR) Definition

Your basal metabolic rate (BMR) is the number of calories your body burns at rest to maintain normal body functions. It is the amount of calories per day your body burns, regardless of exercise. It changes with age, weight, height, gender, ethnicity, diet and exercise habits.

An average BMR would be 1850 calories per day for an adult man and 1500 calories per day for an adult woman of average height and weight.

This is the number before factoring in any movement, it is below even the sedentary level. Once you add in what it take to simply move around for basic functions, while still being sedentary, the average calories per day needed would be 2200 for the man and 1800 for the woman.

Calculating Your BMR

Basal Metabolic Rate Calculator:  Input your height, weight and age and adjust for your activity level to find out how many calories you can eat and maintain body weight. In order to lose weight, you would want to eat fewer calories and/or burn more calories through exercise. This calculator uses the classic Harris-Benedict equation for energy expenditure.

Basal Metabolic Rate - Burning Calories Even at Rest

You may think your Fitbit is fibbing or broken when it tells you that you've already burned a few hundred calories when you get up in the morning. What, you wonder, was I running in my sleep? No, it is simply reporting the calories you burned due to your basal metabolic rate.

Your body burns calories from simply doing the basics it has to do to keep you alive. In fact, most of the calories are burned maintaining the fluid balance in our tissues, at the cellular level. Some of the larger processes that are burning calories at rest include:

  • Breathing: The muscle of your diaphragm has to contract and expand through each breath, so your lungs can expand and contract to bring in oxygen and expel carbon dioxide.
  • Heart Beat and blood circulation: The heart muscle also burns calories as it contracts during each heartbeat. There are also muscle fibers around your blood vessels. You are expending energy to deliver blood to your tissues and take away waste products.
  • Brain and nerve function: The brain actually burns a lot of calories, and it is active even when you are asleep. Your nerves are constantly monitoring your organs and firing to keep the heart and lungs working.
  • Temperature maintenance: Cells throughout your body and organs need to be at 98.6F or nearly that to function correctly. Your body burns calories to keep you at that temperature, warming you up and cooling you down.
  • Organ functions: Your stomach and intestines continue to digest food, absorb nutrients and eliminate waste day and night. The liver, pancreas and kidneys are also continuously at work doing their jobs of maintaining filtering your blood, breaking down nutrients and eliminating wastes.

Can You Boost Your Basal Metabolic Rate?

Exercise is an important factor in the total number of calories you burn per day.

  You can burn hundreds of extra calories per day through physical exercise. The question is, can you increase the calories your body is burning when you aren't exercising?

More lean body mass results in a higher basal metabolic rate, so maintaining the muscle mass that you already have is important, whether or not you are dieting. Just how much adding extra muscle might increase your BMR is a matter of debate. You will see a variety of studies that support or disprove different types of exercise to boost your metabolism.

More: How to Boost Your Metabolism


Estimated Calorie Needs per Day by Age, Gender, and Physical Activity Level. Center for Nutrition Policy and Promotion, USDA. USDA Food Patterns.

Harris J, Benedict F. A biometric study of basal metabolism in man. Washington D.C. Carnegie Institute of Washington. 1919.

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