You are still a senior, don't go on a diet. This will affect your study. I have been there before. I suggest you use fruit instead of dinner at night. This should help. You can also eat oats. If you are not far from the school, you can walk there. Especially eating in the morning can consume some calories. Don't always sit in the classroom between classes. Go out for a walk When climbing stairs, you can stand on tiptoe, which can thin your legs.