People need to eat to live, but they don't need to eat junk food to live. Sure, it's possible for people to get fat overeating real food. But I doubt it's all that common. I've never known a fat person who didn't essentially live on empty calories. If someone is really incapable of moderation and can't eat junk food as an occasional treat rather than a normal part of their day? Then they need to just give up junk food.  I'm not saying junk food itself is a problem. No more than alcohol is a problem for the world rather than just to alcoholics. But we have a pretty clear picture of before and after when it comes to the acceptance of junk/fast food as a normal part of life.