BMR (Basal Metabolic Rate), the basal metabolism, is the number of calories your body needs to sustain its vital functions at complete rest. It is the energy used for the work of the heart, breathing, maintaining body temperature and the work of the brain — before you do any activity at all. BMR usually accounts for 60–70% of total daily energy expenditure.
How BMR Differs from TDEE
BMR is the absolute minimum of energy at full rest. When we multiply it by an activity multiplier, we get TDEE — the total daily requirement covering movement, digestion and exercise. BMR is therefore the foundation on which the full calorie balance is built.
The Mifflin-St Jeor Formula
The most accurate modern formula for BMR takes into account body weight, height, age and sex:
- Men: BMR = 10 × weight[kg] + 6.25 × height[cm] − 5 × age[years] + 5
- Women: BMR = 10 × weight[kg] + 6.25 × height[cm] − 5 × age[years] − 161
Calculation Example
A man: 40 years old, 85 kg, 180 cm.
- BMR = 10 × 85 + 6.25 × 180 − 5 × 40 + 5
- = 850 + 1125 − 200 + 5
- = 1780 kcal
This means that this person's body uses about 1780 kcal per day solely to sustain vital functions — even if they spent the whole day in bed.
What Affects BMR
- Muscle mass — muscles use more energy than fat, so they raise BMR
- Age — BMR declines with age as muscle is lost
- Sex — men usually have a higher BMR due to greater muscle mass
- Body weight and height — a larger body needs more energy
- Genetics and hormones — e.g. thyroid function significantly affects the rate of metabolism
Why It Is Worth Knowing Your BMR
Knowing your BMR helps set a safe calorie level. Eating below your BMR for an extended time slows the metabolism, leads to muscle loss and deficiencies. That is why, even during weight loss, you should not go below your basal metabolism without specialist supervision.
Can You Increase BMR
Yes, though to a limited extent. Building muscle mass through strength training gradually raises BMR. The following also help: adequate protein intake, good sleep and avoiding extreme, prolonged diets that lower the metabolic rate. There are, however, no miracle ways to dramatically "speed up" the metabolism.
Remember
BMR formulas give an estimate for healthy people. Thyroid conditions, medications taken and individual differences can significantly change the actual metabolic rate. When planning a therapeutic diet, consult a doctor or dietitian.
Want to find out your basal metabolic rate? Enter your weight, height, age and sex in our BMR calculator on liczbnik.pl and it will calculate your result and an approximate TDEE.