You can only eat eggs, tomatoes, milk, cucumbers and other low-calorie foods, but you won't lose more than a catty after eating them. It is no problem to lose 15-20 kg in a short time, but it will generally rebound. Moreover, if you are 23-25 years old, it is best not to lose weight in this way, which will have a certain impact on your health, because the energy you need every day at this age is not met and your weight changes.
So it's better to exercise and eat at night.