Definition
Basal metabolic rate (BMR) is the amount of energy your body spends at complete rest to keep its vital functions running: heartbeat, breathing, brain activity, body temperature regulation, and cell turnover. It's the biggest chunk of your daily energy expenditure — around 60 to 70% of the total.
Detailed explanation
Why basal metabolic rate matters
Understanding your basal metabolic rate is understanding your body's energy floor. Even if you spent the whole day lying down without moving, your body would still need this minimum energy to function properly. It's the level you should never drop below in terms of calorie intake.
BMR depends on several biological factors: your age (it drops about 1 to 2% per decade after 20), your sex (men generally have a higher BMR due to greater muscle mass), your height, your weight, and especially your body composition. The more muscle you have, the higher your basal metabolism, because muscle burns more energy at rest than fat tissue.
The calculation formulas
The most widely used and scientifically validated formula is Mifflin-St Jeor (1990):
- Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
- Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161
For example, a 35-year-old woman weighing 60 kg and 165 cm tall has a BMR of about 1,294 kcal. That means her body burns 1,294 calories per day just by existing.
BMR and dieting
A common problem with overly restrictive diets is that they crash your BMR. When you eat well below your BMR for several weeks, your body adapts by lowering its energy expenditure. This effect, sometimes called metabolic adaptation, makes weight loss harder and harder and encourages regain when the diet ends.
That's why nutritionists recommend never eating below your BMR, even during a calorie deficit.
In practice
To quickly calculate your basal metabolic rate, use the calorie calculator, which builds in the Mifflin-St Jeor formula. Once you know your BMR, multiply it by an activity coefficient to get your total expenditure (TDEE).
To maintain or raise your basal metabolic rate, bet on resistance training. Every kilogram of muscle you gain raises your BMR by about 13 kcal per day. Over the long run, that adds up. Also make sure you're sleeping enough (7 to 9 hours) and managing your stress — lack of sleep and cortisol can hurt your metabolism.
Useful links
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