To be honest, I don't think food has much to do with it. My sisters (6,6,12) watch tv almost all day. My mom, when she does cook, makes ground hamburger with anything she can find, otherwise they eat pizze and fast food several times a week. Half her grocery bills are junk food. But all three of them are average wieght or under.
That's my family. Well in the summer we are barley in the house but in the winter everyone stay inside (for obvious reasons!) I am underweight but I eat lots of junk food and sit on my butt all day. But I'm not anorexic or belemic and I don't think I'm fat. I have a few friends who are fat and they bmx and eat semi-healthy but dont seem to loose weight (they bike ALL the time and every day in the summer) so they are very active. I don't think you should be blaming the parents, tv, or food for alot of people (well less then majority) it's just the way they are built.