This is a great question, because prevention is the best medicine!
First, engage your teen in daily physical activity and cut down sedentary behaviors (TV, computer, viseo game time, etc.).
Second, teach him or her healthy eating habits:
1. Eat breakfast, lunch, dinner. No meal skipping as it makes the body think that it will be starved, so it will convert all calories into fat.
2. Fruits and vegetables should be included in every meal/snack.
3. Stop drinking pop and juice. Both are loaded with sugar that is not needed for health and growth.
4. Stop eating fast food. Nothing about fast food is heathy.
5. Learn to cook! That can be a fun family activity that produces yummy and healthy meals, and saves you money in the long run!