Calorie needs

Three numbers that organise any diet: what your body burns at complete rest (BMR), what you actually burn in a day (TDEE), and how much to eat to lose weight at a chosen pace. Calculated with the Mifflin-St Jeor equation, the most accurate formula in common use.

How it works

BMR uses the Mifflin-St Jeor equation (10×weight + 6.25×height − 5×age, +5 for men / −161 for women); TDEE multiplies it by an activity factor. The deficit follows from simple physiology: a kilogram of body fat stores roughly 7,700 kcal, so losing 0.7 kg a week takes a deficit of about 770 kcal a day.

The most common mistake

Overrating your activity. A desk job plus three workouts is "moderate", not "high". If the scale will not move despite a paper deficit, nine times out of ten TDEE was overestimated or weekend calories never made the log.

"Below BMR" explained: can I even eat less than my organs need?

Yes, and physically nothing breaks. BMR is what your organs burn at rest, but that energy does not have to come entirely from food: during a deficit your body fat supplies the gap. That is the entire mechanism of losing weight; the brain and heart get their fuel whether it arrived from a plate or from stored fat.

So why the warning? Because eating below BMR without supervision is usually a bad trade: hunger becomes hard to sustain, muscle loss accelerates, and the rebound after the diet gets more likely. Treat BMR as a practical floor for everyday dieting, not a physiological limit; medically supervised diets go far below it safely.

And if your target for 0.5 kg a week lands below BMR, it does not mean that pace is impossible. It means your TDEE is too low to support it through food alone. Two honest fixes: raise TDEE by moving more (daily steps, one extra session; the same weekly loss then fits above BMR) or pick a slower pace and let it take a few weeks longer.