A modest calorie deficit is key here, not a substantial one, because this needs to be a daily calorie amount you can sustain. If you cut too many calories, you'll be too tired to work out and will feel hungry all the time, constantly thinking about food. What's worse is that you'll be more likely to give up.
You can calculate your calorie deficit by multiplying your bodyweight by 10 to 12. Your caloric intake should fall somewhere within these numbers. Another way to calculate your calorie deficit is to figure out your TDEE (total energy expenditure, which is the number of calories your body burns each day) and subtract 500 calories. Make sure you're always eating more than 1,200 calories each day, even more if you're working out regularly.
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