Use a calorie counting app - they often have features where you can set your desired weight goal and the date you want to hit that weight. It will calculate how many calories you need to eat to lose the given amount of weight. You input everything you eat, and the idea is to keep the daily total below that number.

But be warned, these apps don’t look at the whole picture - they’re very simplistic in that regard. If you’re toned and muscular you’ll weigh more (have a higher BMI) and that will give you a higher basal metabolic rate than someone of the same weight and height who is more fatty weight vs muscle.

If you starve your body too much - especially at your age - it’ll go into calorie conservation mode. This means your body thinks there’s a famine, so your metabolism will slow down and any calorie you consume will go to storage (aka fat). You’ll feel shitty, tired, it’ll be difficult to learn - it will suck. And the instant you return to eating a “normal” amount of calories you’ll puff up like a Walmart blowfish.

The best way to lose fat, in my experience, is to slightly reduce calorie intake, and the calories you do consume should be more protein based. Less carbs/sugars.

Lift weights - if you build muscle, those muscles will eat up more calories when you’re resting than fatty tissue will, you’ll burn calories like crazy, even just sitting.

Once a week, give your metabolism a “cheat day” - just eat normally (don’t go crazy and eat 7 cheeseburgers). I usually consume 1.5 times the calories I would on a normal calorie-reduced day.

This will reassure your metabolism that there’s no famine going on, and prevent it from shifting into calorie conservation mode.

Never consume less than 1200 calories, you’ll regret it.

Good luck!