If you’re aiming to lose weight safely the rule of thumb is 3 lbs a week. 3000kcal per pound works out to an average deficit of about 1280 calories per day. Max.
Obese people can lose a bit more under doctor supervision. My understanding is that it’s tied partially to % of body weight lost per week and partly to what your organs can process, which does not increase with body mass.
I don’t think absolute numbers are very useful here. You need around 5–10% reduction in calorie intake to get any weight-loss effect going, and I wouldn’t reduce by more than 20% (relative to weight-maintaining intake — it’s different if you’ve been seriously overeating) if you want it to be sustainable longer-term.
So for example if your weight is stable at 2500 kcal per day, I would start by reducing the intake by 250–500 kcal, but not more. If this works well for a month or two and then you want to lose weight faster, you can still reduce your intake further. You generally have to do that anyway even just to maintain the velocity, because weight loss also tends to reduce calorie expenditure.
First and foremost, you need to monitor your calorie intake against weight. Here is a useful text about that: https://www.fourmilab.ch/hackdiet/
Your body will get more efficient at whatever exercise you do to make the calories work out. So over time you’ll either have to increase your exercise or rein in the calories a bit more to achieve a sustained result.
That is assuming that you do any exercise. But yes, and the method I linked to explains how to handle any such variation in calorie expenditure regardless of its cause.
Obese people can lose a bit more under doctor supervision. My understanding is that it’s tied partially to % of body weight lost per week and partly to what your organs can process, which does not increase with body mass.