We have made some nutritional changes to the family diet at home. We are limiting sugar and providing healthier snacks and fruits and veggies for all of us. However, I have reason to believe that our 13 yr old is trading out food at school and eating other's junk food when offered. She has also bought snacks with her own money from the cafeteria. We are concerned about obesity and diabetes that runs in the family. How should we handle this?