Science's Biggest Failure: marketing, communication and lobbying.
While it's right that we learned a lot about diet in the last decades, all the "problems" cited here are pushed by marketing and food corporations, not science:
"Eating lots of peanuts, avocados, and cheese, for example, probably decreases your appetite and keeps you thin."
It was bullshit and it is bullshit. Eating a lot of basically anyhting gets you fat. My guest: USA population. Of course, snack makers will say otherwise.
"I used to think vitamins had been thoroughly studied for their health trade-offs. They haven't. The reason you take one multivitamin pill a day is marketing, not science. "
Bullshit the former, of course right the later. It has never been the standard that a healthy person needs any kind of vitamin suplement aside of what comes with a varied and healthy diet. Big pharma will say otherwise, of course.
"I used to think the U.S. food pyramid was good science. In the past it was not, and I assume it is not now."
Learn a bit of US food pyramid and the impact of lobbies on its redaction. Oh, and it's not so much that older food pyriamids were utterly wrong (basically relative importance of carbs versus veggies have changed roles), but the way to get your dose (too much prefab) and the dose itself (USA standard portions are about double than needed -remember Paracelsus: ...It is only the dose which makes a thing poison.") Again, marketing and communication.
"I used to think drinking one glass of alcohol a day is good for health, but now I think that idea is probably just a correlation found in studies."
Here you have a point but, again, science has gone as far as saying something on the lines of "a glass of wine" (not just alcohol, mind you, never heard that a glass of whisky a day was healthy at all) was probably liminary benefitial, current trend says there's probably not a healthy minimum for alcohol, so a glass of wine a day goes from "minimally benefitial" to "minimally harmful", not a great issue. Of course, wine and beer producers want to make a lot more noise than that.
"the direct problem of science is that it has been collectively steering an entire generation toward obesity, diabetes, and coronary problems."
Bullshit. That's a direct problem of the food industry lobbying and marketing left and right.