To add one more thing, Pollan seems bent on trying to use logic to solve this supposed mystery. He says things like:

"People’s eating choices are more fundamental and closely tied to their identity than their driving decisions or how they choose to heat their house or anything else," Pollan says. "If you challenge my right to have a cheeseburger, that’s getting a little intimate." And so politicians steer clear of anything that sounds critical of the American plate.

That's bullshit. Smoking is a personal choice, too, but tobacco farmers were pretty limited to NC and a bit else here and there. No matter how much money PhilipMorris ever spent buying votes, the political fallout was limited to two Senate seats, not nearly enough to make a filibuster last. Fallout from bringing down the hammer on Big Ag would be catastrophic for whichever party decided to pull the trigger (Dems, most likely). Go on a map of the US and count the Ag states. My guess is that it's between a third and a half. Logic from an individual's perspective has literally nothing to do with why no one will attempt to regulate the food industry. They don't try, because they know the only thing that will happen is that they will get pummeled in the next election.