Dear Lucy: How do I figure out my basal metabolic rate (BMR)? When it comes to the number of calories I consume each day, should I aim for this number to maintain my weight? —Calorie Counting Cutie
Dear C3: For help with this question, Lucy went straight to the source of all knowledge caloric and dietary: MIT Medical nutritionist Anna Jasonides, R.D.
“This is an easy question,” Jasonides told Lucy happily, and immediately began scribbling mathematical formulas on a piece of scrap paper. “An individual's basal metabolic rate, or BMR, is the total number of calories required to keep the body functioning while at rest,” she explained. “It's the minimum number of calories your body needs to keep your heart pumping, make new blood cells, and maintain respiration, body temperature, digestion, and other intrinsic metabolic processes and chemical reactions.
“But if you plan on getting out of bed for at least part of each day, you don't want to base your caloric intake on your BMR!” Jasonides exclaimed. “What you need to do is to figure out your BMR, and then multiply it by a number representing your level of physical activity. That result is your TDEE, or ‘total daily energy expenditure’—and your TDEE is a pretty good estimate of the number of calories you should consume each day to maintain your current weight.”
Jasonides explained how to figure BMR, using one of these formulas:
BMR = (10 x weight in kilograms) + (6.25 x height in centimeters) – (5 x age in years) – 161
BMR = (10 x weight in kilograms) + (6.25 x height in centimeters) – (5 x age in years) + 5
Then, she continued, to determine TDEE, simply multiply your BMR by the activity factor that most closely describes your level of daily exercise, as follows:
|Exercise level||Activity factor|
|Lightly active (light exercise/sports 1–3 days/week)||1.375|
|Moderately active (moderate exercise/sports 3–5 days/week)||1.55|
|Very active (hard exercise 6–7 days a week)||1.725|
So, for example, a moderately active 35-year-old woman who weighs 155 pounds (or 72.6 kg.) and is 5'6" (or 167.64 cm.) tall would calculate her TDEE as follows:
BMR = (10 × 72.6) + (6.25 × 167.6) – (5 x 35) -161
= 726 + 1047.5 – 175 – 161
TDEE = 1437.5 × 1.55 = 2228.125
In other words, this woman should consume approximately 2228 calories per day to maintain her current weight.
Jasonides emphasizes that these calculations do not yield precisely accurate results. For example, a different calculation to achieve a more exact BMR estimation can be performed based on lean body mass as opposed to total weight (that formula, for both men and women, is BMR = 370 + (9.8 × lean body mass in pounds). Also, any estimation of one’s activity level is just that—an estimation. But calculating your TDEE using either BMR formula will provide you with a baseline number that can be useful in dietary planning. —Lucy
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