Step one: find your maintenance
Maintenance is the intake at which your weight stays stable. Estimate it with a TDEE calculator, or simply use your current intake if your weight has been steady. This is the reference point for everything else — without it, any 'calorie target' is a guess.
Step two: choose a deficit
A deficit of 300–500 kcal a day produces roughly 0.5–1 lb of loss per week, because about 3,500 kcal corresponds to a pound of fat. That pace is sustainable and protects muscle. Larger deficits work faster at first but are harder to hold and tend to cost lean mass.
Step three: protect protein and muscle
In a deficit the body can burn muscle as well as fat. A high protein intake — roughly 1.6–2.4 g per kg of body weight — plus resistance training is the best protection. Protein also keeps you fuller, which makes the deficit easier to hold.
Step four: adjust from real data
Track your weight for two to three weeks. If the weekly average is falling at the rate you want, hold. If it is flat, cut 100–200 kcal or add activity. If it is falling faster than about 1% of body weight a week, eat a little more to protect muscle. The trend is the signal, not any single morning's number.
Why the number keeps changing
As you lose weight your maintenance falls, so the same intake becomes a smaller deficit. Water retention can also mask fat loss for a week or two. Recalculate after every 4–6 kg lost, and use waist measurements alongside the scale.
When to get help
Pregnancy, breastfeeding, diabetes, thyroid conditions, a history of eating disorders and some medications all change what is safe. In those cases, work with a doctor or dietitian rather than applying general guidelines.