If you read some of Michael Pollan's books, one of the key observations that he makes about the food system is that people assume organic/natural/etc. foods are expensive when in fact most of the stuff you buy at the grocery store (and fast food joint) is made artificially cheaper. The #1 culprit of this is the subsidizing of the corn industry. Corn is the source of the corn syrup that ends up in all of those soft drinks, snacks, salad dressings etc. On the protein side of it, it's used as the primary feed for cows and other animals. So you have junk food that's cheaper than it ought to be at the grocery store and fast food that's cheaper than it ought to be at your favorite drive-through.

I'm not sure why we keep looking downstream at the problem when there is in fact an underlying SINGLE cause upstream that can address a lot of the issues. Remove the subsidies, allow food to cost a bit more, financially incentivize people to eat 1) better food and 2) smaller quantities of food, and let the downstream problems like obesity, diabetes, etc. take care of themselves.