About the BMR calculation
Basal Metabolic Rate is the energy your body spends keeping you alive with zero activity: breathing, circulation, cell repair, brain function. It typically accounts for 60–70% of everything you burn in a day, which is why it is the starting point for any calorie target.
Formula
Mifflin-St Jeor:
Men: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age + 5
Women: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age − 161Worked example
A 25-year-old man, 175 cm and 70 kg: (10×70) + (6.25×175) − (5×25) + 5 = 700 + 1093.75 − 125 + 5 = 1,674 kcal/day.
Frequently asked questions
Why Mifflin-St Jeor rather than Harris-Benedict?
Mifflin-St Jeor was validated in 1990 against modern populations and is consistently more accurate, typically within about 10% of measured values. The Harris-Benedict equation dates from 1919 and tends to over-estimate.
Should I eat at my BMR?
No. BMR excludes all activity and digestion. Eating at BMR for any length of time is a severe deficit. Use your TDEE as the baseline and adjust from there.
Why does BMR fall with age?
Lean tissue is metabolically expensive, and muscle mass declines from roughly the fourth decade onward unless it is actively maintained. Resistance training is the most effective way to slow that decline.
Sources
- Mifflin MD, St Jeor ST, et al. — A new predictive equation for resting energy expenditure (1990)