> The question is whether some foods are inherently addictive, at least for some people who are more predisposed to food addiction.
In some sense, yes, because to get to extremely high weights, you need to consume extremely high amounts of food. Your stomach will grow, but I would imagine a person would struggle to eat enough carrots to weigh 500 pounds. Quick napkin math says some obese people eat 6700 calories a day. 50 calories is ~12 baby carrots. That's ~1608 baby carrots per day. If my math is right, that's about 67 one pound bags of baby carrots per day.
Carrots are probably an extreme example, but I think the point stands that to get that overweight on healthy food, both the volume of the food and the time required to eat it become astonishing. I don't even know if we can metabolize carrots fast enough to eat that many in a day without rupturing some part of your stomach.
> "Normal" cooked meals that were the staple of nutrition before the advent of fast food are almost absent from their diets.
I think this is a big part of it. Calorie dense food has always been around. The problem was that it was often difficult and/or expensive to make. How long would it take you to replicate a Big Mac combo meal, and how much would it cost? It takes a while, especially given grocery shopping, and it's probably not much cheaper. Likewise, I can go to the grocery store and buy a whole cheesecake for like $10.
Honestly, I think the best way to tackle it is not to outright ban the foods, but just add an excise tax. If we added a 10% tax to soft drinks, fries and pizza, it probably wouldn't make a huge difference to the average citizen's spending. It would be a 10% increase in your food budget if that's all you eat though. If you want to go crazy, add a program that lets you earn that back by doing healthy things, like riding a bike. We should probably do that anyways. If we want to reduce the amount of driving people do, paying them walk/bike places instead of driving isn't a bad system either.