What is a healthy diet and amount of exercise for a 15 year old?

Hello. Are you asking about diet to loose weight or just a diet so you remain or get healthy? If you are healthy 15 year old with normal weight ( you can calculate your ideal and healthy weight via BMI calculator) you should not worry much about what you are eating. You are in development, your muscles grow, your bones grow now and you need a lot of energy for these processes. So dont worry if you eat couple of burgers or fries or drink soda. Its all energy and might help you a little. Of course you should be eating healthy stuff, a lot of vegetables and fruits that are full of vitamins, you also need those. AS for the exercise you might consider starting some sport that you like, maybe soccer, football, basketball, swimming , table tennis and exc. You should exercise for at least 3 hours per week in order to stay in good shape.