Your Basal Metabolic Rate - The Foundation of Calorie Needs
BMR is the number of calories your body burns at complete rest - just to stay alive. It drives 60-75% of your daily calorie burn. Knowing your BMR is the starting point for any weight loss, maintenance, or muscle gain plan.
What Is BMR?
Basal Metabolic Rate (BMR) is the energy your body needs to perform essential functions at rest: breathing, circulation, cell production, and temperature regulation. For most adults, BMR accounts for 60-75% of total daily calorie burn.
The Mifflin-St Jeor Formula
Women: BMR = 10w + 6.25h - 5a - 161
- w = weight in kg
- h = height in cm
- a = age in years
Worked Example: 40-Year-Old Man
- Weight: 82 kg
- Height: 178 cm
- Age: 40
- BMR = 10(82) + 6.25(178) - 5(40) + 5
- BMR = 820 + 1,112.5 - 200 + 5 = 1,737 calories/day
BMR vs TDEE
| Term | Definition | Typical Value |
|---|---|---|
| BMR | Calories burned at rest | 1,400-1,800 |
| RMR | Resting metabolic rate (slightly higher) | 1,500-1,900 |
| TDEE | Total daily energy expenditure (BMR × activity) | 1,800-3,500 |
What Affects Your BMR
- Muscle mass - more muscle, higher BMR
- Age - BMR declines about 2% per decade after 20
- Sex - men average 5-10% higher BMR than women
- Body size - larger bodies burn more calories at rest
- Thyroid function - hypo/hyperthyroidism shifts BMR
- Genetics - natural metabolic variation
Frequently Asked Questions
What is a normal BMR?
Most adult women: 1,200-1,600 calories/day. Most adult men: 1,500-2,000 calories/day. Athletes and larger individuals often exceed these ranges.
Can I increase my BMR?
Yes - resistance training builds muscle, which raises BMR. You cannot change age or genetics, but you can change body composition.
Is BMR the same as metabolism?
BMR is the largest component of metabolism. Total metabolism also includes digestion, exercise, and non-exercise activity.
Why is my BMR lower than others?
Age, sex, size, and body composition all matter. A smaller, older woman will naturally have a lower BMR than a larger, younger man.
Should I eat my BMR calories?
Never eat below your BMR for extended periods - it risks muscle loss and metabolic slowdown. Eat at or above BMR plus a portion of activity calories.
How accurate is BMR calculation?
Mifflin-St Jeor is accurate within +/- 5% for most adults. Direct measurement requires a metabolic cart or DEXA-derived estimate.