Knowing your basal metabolic rate (MB) allows you to determine how many calories your body needs when you are trying to lose weight, maintain it or increase it. Your basal metabolic rate corresponds to the amount of energy consumed by your body in resting conditions. It is the energy needed for the functioning of the organs and to stay alive without taking physical activity into consideration. Your MB is affected by a large number of variables. Gender, age, height, and weight are the most important factors of all, but your body's fat percentage, your diet, exercise habits, and overall health also play a role. Read on to find out how to calculate yours.
Steps
Method 1 of 2: Calculating the Basal Metabolism for a Man
Step 1. Measure your height in centimeters
Generally, the bigger you are, the higher your MB will be. All other things being equal, a tall man has more tissue than a shorter one, which means he consumes more energy every day. If you are unsure of your height, measure it exactly. Calculate it in centimeters, the unit of measurement used in the formulas presented in this article.
- Position yourself with your back and heels against a wall, staying straight. Have someone mark the exact spot where your head goes. Measure the height of that point with a measuring tape.
- If you know your height in inches, you can multiply it by 2.54 to convert it to centimeters.
Step 2. Determine your weight in kilos
If you haven't weighed yourself in a while, step on a scale. Generally the heavier you are, the more energy you will consume. Weighing yourself is a good idea if you are trying to lose or gain weight, because you will be able to judge your progress based on an initial value.
- If you know your weight in pounds, you can convert it to pounds by multiplying it by 0.454.
- If you are trying to lose or gain weight, remember that this can fluctuate around 2.5 pounds throughout the day, based on when you drank or ate, when you went to the bathroom etc. If you are starting a journey to change your weight, weigh yourself once a week at the same time while wearing similar clothes.
Step 3. Use the equation for the men's MB
If you are a man, use the following equation: MB = 66 + (13.7 x weight in kg) + (5 x height in cm) - (6.8 x years of age). This simple equation takes into account height, weight, age and gender. MB increases with weight and height and decreases with age.
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The MB value in this equation is expressed in kilocalories per day.
In common parlance, kilocalories are often referred to simply as calories - you've probably seen them on food nutrition tables.
Step 4. Learn the other factors that can affect your MB
The equation presented in this article is not perfect, it is just a useful method of approximating your MB. Personal MB varies based on many factors, including:
- Muscle mass. Leaner, more muscular bodies have higher MBs than fat ones. An 80 kg Olympic swimmer with a near-zero body fat percentage will have a much higher MB than an 80 kg man with an average body fat percentage.
- Growth. Growing teens, as well as people who need to regenerate tissue after an injury have higher MBs.
- Body temperature. High body temperature (caused for example by fever) can increase MB.
- Diet. Fasting or eating a crash diet can decrease your MB because your body compensates for lack of energy.
- Hereditary factors. Some people simply inherit their metabolism from their parents - if you've known someone who can eat a lot without gaining weight, that person probably has naturally high MB.
Method 2 of 2: Calculate the Basal Metabolism for a Woman
Step 1. Measure your height and weight
As with men, a woman's MB can vary a lot based on height and weight. For an accurate measure of your MB, calculate this data exactly. Use metric units - centimeters for the height and kilograms for weight - because they are the units required by the equation.
- To convert your height in inches to centimeters, multiply it by 2.54. To convert your weight in pounds to kilograms, multiply it by 0.454.
- If you are trying to lose or gain weight, remember to weigh yourself about once a week, always at the same time. Your weight can fluctuate 2.5kg or more throughout a day.
Step 2. Use the equation for women's MB
Since women often (but not always) have less lean mass than men, they will generally have lower MBs. The equation takes this factor into account, multiplying height and weight by smaller values. However, since women's metabolism decreases less with age than men's, this multiplication factor is also lower. For women, the MB equation is: MB = 655 + (9.6 x weight in kg) + (1.8 x height in cm) - (4.7 x years of age).
Again, the MB value in this equation is expressed in kcal (kilocalories) per day
Step 3. Be aware that pregnancy can affect MB
As with men, diet, growth, body temperature, muscle mass, and hereditary factors can also affect a woman's MB. In the case of women, pregnancy can also have a significant impact on MB. Pregnant (or nursing) women will have higher MBs than other women. Feeding a growing baby (and later producing breast milk) takes more energy - if you've ever noticed a pregnant woman's appetite goes up a lot, you've seen this effect in action.
Advice
- Once you have determined your MB, you can multiply it by an activity coefficient to calculate your Total Daily Energy Expenditure, and thus estimate the total number of calories you burn in a day. The activity coefficient for sedentary people is 1.2, for people who perform moderate physical activity (light exercises 1 to 3 times a week) it is 1.375, for moderately active people (moderate exercises 3 to 5 times a week)) is 1.55, for very active people (demanding exercises 6 to 7 times per week) it is 1.725, and for extremely active people (daily hard exercise or more workouts per day) it is 1.9.
- If you have measured your body composition, you can use your lean mass to calculate the MB very accurately. Body composition measures the percentage of fat mass contained in your body. Any weight that does not correspond to fat mass is considered lean mass. This equation does not change based on gender. MB = 370 + (21.6 x lean mass in kg)
