What BMR means
Basal metabolic rate is the energy your body needs to keep running at complete rest: breathing, circulation, temperature and cell repair. For most people it makes up around 60–70% of daily energy use. Your total daily needs are higher, because they include digestion and movement.
The three BMR equations
| Equation | Men | Women |
|---|---|---|
| Mifflin-St Jeor (1990) | 10W + 6.25H − 5A + 5 | 10W + 6.25H − 5A − 161 |
| Harris-Benedict, revised by Roza and Shizgal (1984) | 88.362 + 13.397W + 4.799H − 5.677A | 447.593 + 9.247W + 3.098H − 4.330A |
| Katch-McArdle | 370 + 21.6 × lean body mass (kg) | |
W = weight in kg, H = height in cm, A = age in years.
Worked example: a 30-year-old woman, 165 cm and 62 kg. Mifflin-St Jeor gives 620 + 1,031.25 − 150 − 161 = 1,340 kcal; revised Harris-Benedict gives 1,402 kcal. With 28% body fat (lean mass 44.6 kg), Katch-McArdle gives 1,334 kcal.
Which equation should I use?
Mifflin-St Jeor is the best general choice; reviews by the American Dietetic Association (now the Academy of Nutrition and Dietetics) found it the most accurate for most healthy adults. Katch-McArdle can be better for lean, muscular people, because it uses lean mass rather than total weight, but only if your body fat estimate is reasonable. Harris-Benedict tends to give slightly higher figures.
Medical note: all three are population estimates. Thyroid conditions, medication and other factors change real metabolic rate. A clinic can measure it directly with indirect calorimetry.
Sources
- Mifflin MD, St Jeor ST et al. Am J Clin Nutr, 1990;51:241–247
- Roza AM, Shizgal HM. The Harris Benedict equation reevaluated. Am J Clin Nutr, 1984;40:168–182
- Frankenfield D et al. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults. J Am Diet Assoc, 2005
Frequently asked questions
What is a normal BMR?
For many adults it falls roughly between 1,200 and 1,800 kcal a day, depending mostly on body size, sex and age. Larger and younger bodies have a higher BMR.
What is the difference between BMR and TDEE?
BMR is the energy used at complete rest. TDEE adds digestion and all your movement, so it is higher. TDEE is roughly BMR multiplied by an activity factor of 1.2 to 1.9.
Which BMR formula is most accurate?
For most healthy adults, Mifflin-St Jeor is the most accurate of the common equations. Katch-McArdle can suit lean, muscular people if body fat is known.
Does BMR fall with age?
Yes, slowly, mainly because muscle mass tends to fall. Strength training helps keep muscle and so supports metabolic rate.