Frankly, I think consumerism is largely to blame.
Consumerism is an ethos. Life is understood to be about consuming things, and in this case, literally consuming food. If you want to eat it, then eat it. Watch how overweight people eat and live. Except for a small percentage of people with metabolic disorders, you'll find your answer there. Consumerism turns traditional virtue on its head. Whereas once a man was a slave to his passions if he couldn't refuse himself their satisfaction, now satisfaction of them is the highest law. We even have the chutzpah to claim that this is the essence of freedom. Oh, how our ancestors weep! Yes, the man who can't control himself is now "free".
Now, because we live in a consumerist society, the market is more than happy to indulge and enable what would have been previously considered a bad gluttonous habit. Junk food on every turn. Even foods that are supposedly healthy have less nutrition than they used to or contain various additives and sugar and all sorts of crap that I suppose people don't understand should be avoided. In turns, these additives can throw your metabolism out of whack. Libertarians will tell you that this is freedom and anything else is socialism, but that's bullshit. If industry is exploiting people's vices for profit, then this isn't freedom and it is the government's role to regulate and criminalize such things to protect people. That government can use protection as an excuse to push nefarious laws and regulation does not mean that it is always the case.
(Mind you, the consumerist citizen is also easier to manipulate by the government, not just industry. If you are unable to refuse yourself things, then the government can better predict how to manipulate you. The same enslavement to one's passions also darkens the mind and makes you less capable of discerning the political control being used against you. It's the same with sexual liberation. Porn is a tool for social engineering and MeToo is the result of consumerism entering the sphere of sexual relations.)