You Can Boost Weight Loss by Knowing Your BMR: Here’s How It Works

The minimum number of calories you need for your body to function is called your basal metabolic rate, or BMR. You burn most of your daily calories with zero effort, movement, or even thinking. Whether you’re sleeping, talking on the phone, working at a keyboard, or simply watching TV, your body is burning calories to keep your organs working — your heart pumping and your lungs breathing. If you know your BMR, you can better determine your caloric needs for healthy weight loss.

The number of calories used to maintain basic bodily functions add up to your BMR. “Basal” essentially means “base.” Think of it as the amount of energy (aka number of calories) that is just enough to cover all your body’s bases.

TDEE is determined by genetics, biological sex, age, body size, and lean body mass. Hormonal health can also affect metabolism.

While many people blame a slow metabolism (they mean BMR) on weight gain, it’s actually true that larger body sizes have higher BMR, explains Tim Church, MD, PhD, the chief medical officer at Wondr Health, a company that provides digital health and weight loss programs.

At rest, a pound of fat burns roughly two calories per day and a pound of muscle burns roughly six calories, Dr. Church says.

That’s why men naturally enjoy a higher BMR than women, as they tend to have more overall body size and lean mass levels, explains Sari Greaves, RDN, a registered dietitian-nutritionist at LBS Nutrition in East Brunswick, New Jersey, and the author of Cooking Well Healthy Kids: Easy Meals for Happy Toddlers.

BMR is often used interchangeably with resting metabolic rate, or RMR, but they’re actually slightly different.

Knowing your BMR or RMR can help you better determine your total daily energy expenditure in order to create a caloric deficit, defined as consuming fewer calories each day than you burn for energy. A caloric deficit is required to lose weight.

But because most people do not have access to state-of-the-art labs to determine BMR exactly, equations are often used to make approximations. The easiest way to measure your metabolic rate is to use an online calculator. You can find many calculators online, and all use varying equations.

Revised Harris-Benedict Equation

Men: (88.40 + 13.40 x weight in kilograms [kg]) + (4.80 x height in centimeters [cm]) – (5.68 x age in years)

For example, if a man is 180 pounds, 5'11", and 43, his RMR is 1,804 calories.

Women: (447.60 + 9.25 x weight in kg) + (3.10 x height in cm) – (4.33 x age)

For example, if a female is 130 pounds, 5'3", and 36, her RMR is 1,333 calories.

Mifflin-St Jeor Equation

The Mifflin-St Jeor equation is another equation that uses the same variables but may be more accurate, Church says.

Here’s what the Mifflin-St Jeor equation looks like for men and women:

Men: (9.99 x weight in kg) + (6.25 x height in cm) – (4.92 x age in years) + 5

For example, if a male is 180 pounds, 5'11", and 43, his RMR is 1,734 calories.

Women: (9.99 x weight in kg) + (6.25 x height in cm) – (4.92 x age in years) – 161

For example, if a female is 130 pounds, 5'3", and 36, her RMR is 1,249 calories.

Cunningham Equation

Other metabolic equations, such the Cunningham equation, use your total level of lean body mass, which is a primary determiner of BMR and therefore RMR. But calculation requires you to measure your body’s levels of fat versus free-fat mass, Church says. Calipers and smart scales are two popular at-home options, but the most accurate measures are performed in professional and laboratory settings.

Here are examples of how to calculate your RMR using the Cunningham equation:

Men and women: 500 + (22 x lean body mass in kg)

For example, if a man is 170 pounds, 5'11", 43, and his body-fat percentage is 20 percent, his RMR is 1,857 calories.

If a female is 130 pounds, 5'3", 36, and her body-fat percentage is 25 percent, her RMR is 1,473 calories.

• Sedentary Little to no exercise, multiply by 1.2
• Lightly Active Light exercise one to three days per week, multiply by 1.375
• Moderately Active Moderate exercise on three to five days per week, multiply by 1.55
• Very Active Hard exercise six or seven days per week, multiply by 1.725
• Extremely Active Hard exercise every day and/or a physical job, multiply by 1.9

If the man in the above example exercises two days per week, his daily caloric expenditure is roughly 2,384 to 2,481 calories.

If the woman in the above example exercises six days per week, her daily caloric energy expenditure is roughly 2,155 to 2,541 calories.

This calculation gives you the estimated number of calories you burn in one day at your current level of activity; this is how many calories you need to consume per day to stay at your current weight.

To lose weight, you need a caloric deficit, meaning that you must either reduce your caloric intake below your total daily energy expenditure or increase your total daily energy expenditure, says Greaves. For example, you can try multiplying your RMR by various activity factors to see how your daily caloric burn would fluctuate with increased exercise.

Strength training provides a more lasting boost to BMR by altering your body’s composition. As previously stated, a pound of fat burns roughly two calories per day while a pound of muscle burns six at rest, Church says. To put that into perspective, gaining two pounds of muscle will increase RMR by about 12 calories.

• Your basal metabolic rate is how many calories your body needs at rest in order to function properly.
• Calculating your BMR and RMR helps you determine an effective caloric intake for weight loss.
• Use trusted online calculators to estimate your BMR and adjust your diet or activity levels according to those estimates.

Additional reporting by Dennis Thompson Jr.