Understanding Your Basal Metabolic Rate
Your Basal Metabolic Rate (BMR) is the minimum number of calories your body needs to perform essential life-sustaining functions, such as breathing, blood circulation, and cell production, while at complete rest. A variety of factors influence your BMR, including age, sex, weight, height, and body composition. Understanding this number is crucial for anyone aiming to manage their weight, whether for loss, gain, or maintenance.
The Difference Between BMR and RMR
While often used interchangeably, BMR and RMR (Resting Metabolic Rate) have a slight difference. BMR is measured under very strict, clinical conditions, often in a research setting. RMR, on the other hand, is the energy your body burns at rest but includes calories used for minimal daily activities like digestion. RMR is typically about 10% higher than BMR and is often what is estimated by online calculators.
The Mifflin-St Jeor Equation
The Mifflin-St Jeor equation is widely considered one of the most accurate formulas for estimating BMR in healthy adults. It uses your weight in kilograms, height in centimeters, and age in years. For the specific formulas for men and women, along with an example calculation, please refer to {Link: NASM https://www.nasm.org/resources/calorie-calculator} or {Link: InBody USA https://inbodyusa.com/blogs/inbodyblog/49311425-how-to-use-bmr-to-hack-your-diet/}.
The Revised Harris-Benedict Equation
The revised Harris-Benedict equation, a formula from 1984, is another well-regarded method for estimating BMR. It uses the same variables as the Mifflin-St Jeor equation, but with slightly different coefficients. The formulas for men and women, along with an example calculation, can be found on {Link: NASM https://www.nasm.org/resources/calorie-calculator} or {Link: InBody USA https://inbodyusa.com/blogs/inbodyblog/49311425-how-to-use-bmr-to-hack-your-diet/}.
Manual Calculation Comparison: Mifflin-St Jeor vs. Harris-Benedict
For a comparison table detailing features, variables, and accuracy of the Mifflin-St Jeor and Revised Harris-Benedict equations, see {Link: InBody USA https://inbodyusa.com/blogs/inbodyblog/49311425-how-to-use-bmr-to-hack-your-diet/}.
Calculating Total Daily Energy Expenditure (TDEE)
Once you have your BMR, the next step is to estimate your Total Daily Energy Expenditure (TDEE), which is the total calories you burn daily. You do this by multiplying your BMR by an activity factor. A table of activity level multipliers can be found on {Link: NASM https://www.nasm.org/resources/calorie-calculator}. An example demonstrating how to calculate TDEE from BMR is available on the same page.
How to Use Your Manual BMR for Weight Management
Manually calculating your BMR helps you determine your TDEE, which is essential for weight management. To lose weight, create a calorie deficit by consuming fewer calories than your TDEE, aiming for 300–500 fewer calories daily for a loss of 0.5–1 pound per week. To gain weight, aim for a calorie surplus, consuming about 15% more calories than your TDEE, especially when combined with strength training. Avoid consuming fewer calories than your calculated BMR, as this can negatively impact your metabolism.
Conclusion
Manually calculating your BMR using formulas like Mifflin-St Jeor or Harris-Benedict provides a valuable insight into your body's basic energy needs. This allows you to accurately determine your TDEE by applying an activity factor and subsequently plan your caloric intake for weight management. While manual calculation is a powerful personal tool, seeking professional advice can provide the most accurate measurements, particularly for body composition.
