The Harvard Nutrition and Fitness Project says child obesity is up 54 percent since the 1960s. Children, of course, do whatever they see adults doing. But at least provide the healthy things. If you're not sure what that entails, ask your doctor or a nutritionist. Probably the smartest trick is to not allow snacking between meals, so the child comes to the table hungry.
Food battles are far less frequent then.
On the other end of the spectrum, some kids especially teen girls don't want to eat at all. They can get away with it in a family without regular mealtimes. My wife, who taught third grade in a Los Angeles-area Christian school, says she could tell within seconds which students returned from morning recess having dug a candy bar out of their lunch bags or backpacks. Sugar and reading groups just don't work well together. Even educators in traditional, rural areas are facing new headaches.