BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest to maintain basic life functions like breathing, circulation, and cell production.
How BMR Works
BMR represents the largest component of daily energy expenditure — typically 60-75% of total calories burned. Even when you sleep or sit still all day, your body needs energy for organ function, temperature regulation, and cellular repair.
The most widely used formula is the Mifflin-St Jeor equation:
- Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
What Affects BMR
Key factors include: body size and composition (more muscle = higher BMR), age (BMR decreases ~2% per decade after 20), sex (men typically have higher BMR due to greater muscle mass), and genetics. Crash dieting can temporarily lower BMR through metabolic adaptation.
Real-World Example
A 30-year-old male, 180 lbs (82 kg), 5'11" (180 cm): BMR = (10 × 82) + (6.25 × 180) − (5 × 30) + 5 = 820 + 1,125 − 150 + 5 = 1,800 calories/day. This is the energy needed just to exist — before any physical activity.
Frequently Asked Questions
What is the difference between BMR and TDEE?
BMR is calories burned at complete rest. TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity factor (1.2-1.9) to account for daily movement and exercise. TDEE is the number you use for weight management.
Can I increase my BMR?
Yes. Building muscle through strength training is the most effective way — each pound of muscle burns ~6 calories/day at rest vs ~2 for fat. Staying active, getting adequate sleep, and avoiding crash diets also help maintain a healthy BMR.
Should I eat below my BMR to lose weight?
Generally no. Eating below BMR can trigger metabolic adaptation, muscle loss, and nutritional deficiencies. A safer approach is eating between your BMR and TDEE — creating a moderate deficit of 500-750 calories below TDEE.