It’s contextual, some people like Sam Feltham can eat up to 5000 kCal / day and still lose weight. Others can eat under 1000 kCal / day and still put it on.
One factor is how much insulin on average they have in circulation during the day. If your insulin is on average greater than 13 mIU/l then your body fat won’t be contributing much energy and your body will give you more hunger signals and if you don’t respond it’ll slow your metabolic rate. If your insulin spends the day on average below 13 then body fat is contributing to your satiation signalling, and you will have abundant energy at your disposal.
Of course some food (protein about half as much as from carbs) will raise insulin, and a ketogenic diet is one that reduces as much as possible the need for insulin.
Your personal hunger/satiation signals will set up a homeostasis to make sure you are adequately fueled, with insulin status setting the levels of how much energy you reserve to store. It’s kind of like you are in a climate controlled room and hunger is the heater and satiation is the A/C and the temperature in the room is how much body fat you store and the thermostat controlling that is how much insulin you make … on average.
If you get to satiety and then eat beyond that … then all bets are off. Your homeostasis will likely try to use more calories for random stuff like giving you crazy legs or making your temperature around your collar bones run a little hotter … but you will also store some of that excess energy. Satiation is key and a ketogenic diet allows us to start to trust that signal again after a lifetime of it being deranged by carbs.
Oh one other thing, you may think your ideal weight is X but your body may think it is Y … your body is factoring in 1000s of factors and optimizing for reproductive survival. I doubt many human bodies optimize for visible abdominals, and most when not deranged by glucose appear to optimize for a gladiator physique with adequate subcutaneous fat to buffer against both weapons and starvation.
If you want body fat lower then you’ll have to trick your body into accepting a non-optimal amount of body fat.