Before any "diet", you need one number: how much does your body burn each day? Here is the accepted scientific way to work it out — with pen and paper.
Why this equation specifically?
The American Dietetic Association reviewed the four best-known equations in a systematic review and found Mifflin-St Jeor the most accurate: it predicts measured resting metabolic rate to within ±10% in a greater proportion of people — both non-obese and obese — than any other equation[1].
The equation
- Men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- Women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
The result is your resting metabolic rate (RMR) — what your body burns if you stayed in bed all day[2].
A full example
A 35-year-old man, 92 kg, 176 cm, office job:
(10 × 92) + (6.25 × 176) − (5 × 35) + 5
= 920 + 1100 − 175 + 5 = 1,850 kcal (resting metabolic rate)
Now multiply by your activity level
- Desk job, little to no exercise: × 1.2 → ~2,220 kcal
- Light activity (walking 1–3 days a week): × 1.375 → ~2,540
- Moderate activity (3–5 days): × 1.55 → ~2,870
- High activity (6–7 days): × 1.725 → ~3,190
This is your maintenance number: eat that and your weight holds. To lose, eat below it by a sensible deficit (commonly 300–500 kcal in practice) and review weekly.
An important caveat — stated in the review itself
Even the best equation misses by more than ±10% in some individuals[1]. The equation is a starting point; your real yardstick is the trend of your weight over two to four weeks. Adjust the number based on reality, not the other way round.