You burn most of your daily calories with little to no conscious effort. Whether you're talking on the phone, working at a keyboard, or just watching television, your body is burning calories to keep your heart pumping, your lungs breathing, and your organs functioning. The calories used to maintain these basic bodily functions add up to your basal metabolic rate, or BMR. Basal essentially means base — think of it as the number of calories that’s just enough to cover all your body’s bases.
"These are what I call your couch-potato calories," says dietitian Sari Greaves, RD, CDN, of Step Ahead Weight Loss Center in Bedminster, N.J. and spokesperson for the American Dietetic Association. "It amounts to 60 percent to 75 percent of the total calories you use daily, and there's no physical activity required for this."
In other words, this is what you burn without lifting a finger. That’s why BMR is also known as the resting metabolic rate, or RMR.
Knowing your BMR can help you create a more effective strategy for weight loss, allowing you to better keep your calorie count on track and better understand the effect exercise will have on your waistline.
Calculating Your BMR
The easiest way to measure your BMR is to use an online calculator. These calculators factor in your height, weight, gender, and age, then assess how many calories you need to eat daily just to maintain your current weight at rest.
You can do the math yourself, using the appropriate equation:
- If you’re a man, your BMR is equal to: 66 + (6.23 x weight in pounds) + (12.7 x height in inches) - (6.8 x age in years). Example, if you’re 170 pounds, 5’11”, and 43, your BMR is 66 + (6.23 x 170) + (12.7 x 71) – (6.8 x 43) = 1,734.4 calories
- If you’re a woman, your BMR is equal to: 655 + (4.35 x weight in pounds) + (4.7 x height in inches) - (4.7 x age in years). Example, if you’re 130 pounds, 5’3”, and 36, your BMR is 665 + (4.35 x 130) + (4.7 x 63) – (4.7 x 36) = 1,357.4 calories
Next figure out your total daily caloric requirement by multiplying your BMR by your level of activity:
- If you rarely exercise, multiply your BMR by 1.2
- If you exercise on 1 to 3 days per week, multiply your BMR by 1.375
- If you exercise on 3 to 5 days per week, multiply your BMR by 1.55
- If you exercise 6 to 7 days per week, multiply your BMR by 1.725
- If you exercise every day and have a physical job or if you often exercise twice a day, multiply your BMR by 1.9
If the man in the example exercises 3 days a week, his daily caloric requirement is 1,734.4 x 1.55, or 2,688.3 calories.
If the woman in the example exercises 6 days a week, her daily caloric requirement is 1,357.4 x 1.725 or 2,342.5 calories.
This calculation gives you the number of calories you burn in one day at your current level of activity; this is the number of calories it takes to stay at the weight you are if you don’t change anything.
Applying Your BMR Calculation to Weight Loss
Once you know your BMR and the number of calories you burn for your activity level, you can improve your weight-loss efforts by setting a lower daily caloric-intake limit and crafting a plan for increasing your physical activity. Here’s how:
Set your daily calorie limit. To lose weight, you need to reduce your caloric intake below your total daily calorie requirement indicated by your BMR + activity level. Putting yourself in a 500-calorie deficit every day should result in the loss of one pound every week, Greaves says.
Adjust your exercise output. Calculators ask for your level of physical activity for a very good reason. You can influence your BMR through exercise, spurring your body to burn more calories even when you are just lounging about.
- Aerobic exercise provides a temporary boost to your BMR, an effect sometimes referred to as after-burn or excess post-exercise oxygen consumption, says Noelle Lusardi, a certified personal fitness trainer who also works at the Step Ahead Weight Loss Center in Bedminster, N.J. This boost drops dramatically following an aerobic workout, with your BMR returning back to its normal level within 15 minutes to 48 hours.
- Strength training provides a more lasting boost to BMR by altering your body's composition. Muscle at rest burns more calories than fat at rest. That's why men naturally enjoy a higher BMR than women, as they tend to have more muscle mass, Greaves explains.
- Increase the calorie deficit by adding more exercise. If you increase the amount of calories you burn off by 250 each day, you’ll lose a half-pound more on top of the calorie cuts made in your diet. You can also increase the intensity of your workouts to burn more calories, and you will increase your calorie deficit and aid your efforts at weight loss.
The advantage of knowing your BMR is that you can adjust the number of calories of any diet you choose to meet your personal guidelines for weight loss.