TDEE: your real daily calorie need
Total Daily Energy Expenditure = BMR × activity multiplier. It's the maintenance line — eat above to gain, below to lose.
Mifflin-St Jeor is the most accurate general formula. Katch-McArdle is better if you know your body fat %.
A 20% deficit drops ~0.5 kg/week sustainably. Aggressive cuts (>30%) lose muscle and adherence; slow lean bulks (+10%) maximise gains with minimal fat.