What is BMR?
Basal metabolic rate is the minimum energy needed to keep your heart beating, lungs breathing, brain working and body warm while lying at rest after fasting. Total daily energy expenditure (TDEE) equals BMR plus physical activity plus the thermic effect of food (about 10%).
How do you calculate BMR?
The Mifflin-St Jeor equation (Mifflin et al., 1990) is the most widely recommended: men = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5; women use −161 instead of +5. A 30-year-old man who is 5'7" (170 cm) and 154 lb (70 kg) has a BMR of about 1,620 calories. Multiply by an activity factor—1.2 for sedentary, about 1.55 for moderately active—to estimate TDEE.
Can you raise your BMR?
Lean mass, mostly muscle, is the biggest modifiable factor, so strength training and enough protein help limit the metabolic slowdown that comes with dieting. A large 2021 study found size-adjusted metabolism stays stable from about 20 to 60 and declines slowly after 60 (Pontzer et al., 2021). Pair BMR with BMI for a fuller picture.
FAQ
- Is it bad to eat below my BMR?
- Short-term it's not dangerous for most adults, but long, steep deficits increase muscle loss. A 300–500 calorie deficit from TDEE is a common recommendation.
- Does metabolism slow down in your 30s and 40s?
- Research suggests not much; reduced activity and muscle loss matter more than age itself before 60.
Sources reviewed: 2026-10-25
References
- Mifflin, M. D., St Jeor, S. T., Hill, L. A., et al. (1990). A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition, 51(2), 241–247.
- Pontzer, H., Yamada, Y., Sagayama, H., et al. (2021). Daily energy expenditure through the human life course. Science, 373(6556), 808–812.