Look for fruits and vegetables without sauces and whole grain cereals and breads. Arrange to special order these foods for you if that is feasible. If you don't feel comfortable speaking to a person in authority, perhaps you could speak to a counselor, friendly teacher or clergyman. Tell them your problem and ask if they could help. Teens especially need healthy choices available to them, as fast and fatty foods are so tempting.
Exercise is another important component of fitness and good health.
It seems hard to believe in this age of fitness enlightenment that your school does not provide some way to exercise, either in a group setting or a gym. Even prisons have fitness programs for inmates. If there are no fitness facilities, you need to work out a schedule that will allow you time to walk briskly for 30 to 45 minutes a day. Again, you need to speak out about this in a tactful way. If this does not produce results, our second suggestion is to speak to your parents or guardians about the situation and let them step in.