You have to be overeating in order to get fat. Some people just make stupid decisions like choosing to overeat, and let their children overeat, despite not having much money  Nailed it. You can lose weight on a calorie-controlled junk food diet! If poor people truly eat cheap junk food because that's all they can afford, they can continue eating junk food, but less of it, and not be fat, and save money. It's so glaringly obvious.