The prevailing sentiment in pop-culture nutrition — propagated in books, blogs, and blather; documentaries and diatribes — is that everything we thought we knew about diet and health until yesterday is wrong.

Actually, we have a much bigger problem than that. To one degree or another, everything we thought we knew about nutrition is right — and we are obligated to do something about it, or stay fat and sick.

That’s a bigger problem for all concerned. For most of us, it means it’s time to stop rolling our eyes at non-existent conspiracies, and actually attempt to eat well and be active. It means there is no scapegoat to blame for all our ills, and no silver bullet to save us. Clearly, that just sucks.

The news is far worse for authors, publishers, and the media. What wonderfully iconoclastic view of diet has any chance of becoming the next best seller once we acknowledge we actually know enough already to eliminate almost all obesity and chronic disease?

None, and that’s clearly unacceptable. If you don’t think Madison Avenue loves our confusion, you must be even more confused than the rest of us.

Some portion of you doubtless agree with me that in fact, we are not confused; that we already do indeed know enough about the basic care and feeding of Homo sapiens for truly stunning public and personal health advances. So now, I am reaching out to the rest of you. I am reaching out to those who think I’m deluded, benighted, arrogant, misguided, or simply wrong.

Try this experiment. If you believe that, for instance, eating more meat is good for us — pretend you wanted to refute that, and search the Internet accordingly. Or, conversely, if you believe that evidence clearly establishes a vegan diet as the “best” for human health, search the Internet diligently pretending to be someone wanting to disprove that. Do your best to read what you find as you would read the material that best conforms to your established worldview. Be sure to look here, by the way, where the peer-reviewed evidence resides.

This same experiment can be applied to any dietary contention you like. If you think saturated fat is harmful, search the literature for evidence it isn’t. If you think it’s beneficial, search the literature for its harms. If you think all of our ills are the fault of omega-6 fat, search the literature for evidence to the contrary. If you think Ancel Keys was a messiah, search the literature for the flaws in his research. If you think Keys was a misguided ideologue, search the literature for the evidence supporting his views. If you think the benefits of low-fat eating are debunked dietary history, search the literature for those purported benefits. If you think animal protein is bad for us, search the literature for benefits of the Paleo diet.

Folks, this is what homework really looks like. This is where genuine scholarship merely begins. The easiest thing in the world is to search selectively for the opinions you already own. You will find them, and find them gratifying. But this is the intellectual analogue to masturbation — self-gratification, signifying nothing.

As far as I can tell, it is on the basis of just such vapid nonsense that we lob convictions and castigations at one another. We are a lazy lot of opinionated buffoons. We are more often than not arrogant enough to think that some number of minutes searching the Web for what we already believed anyway is the equivalent of years of dedicated training and a diligent attempt at unbiased interpretation. We are the malleable pawns of big food, big pharma, big media, and big business — who help propagate our pseudo-confusion, and profit from it.

If we ate better food, we would need fewer drugs. If we knew what to eat, there wouldn’t be a new diet book and diet story to peddle every day. Are you actually naïve enough to believe that our collective confusion isn’t aided and abetted by those banking on it? Well then, maybe you’d like to buy a bridge along with your diet soda and fries.

And we barely need any help to play the part of dolts anyway, because it’s a wonderful way to procrastinate. We would rather renounce yesterday’s diet and try today’s, then deal with the time-tested fundamentals of losing weight and finding health. That doesn’t involve a scapegoat or silver bullet, so it can’t possibly be a good idea.

And just to be clear, absolutely nothing currently capturing the public imagination about diet and health is new. Absolutely nothing. I have a copy of The Carbohydrate Addict’s Lifespan Program on my bookshelf with a 1997 copyright. My copy of Sugar Busters dates from 1998. And yet, we are so resistant to the notion that we already know enough to do something that we believe it when we are told — nearly 20 years later — that excess sugar in our diets is the scandal “no one” is telling us about. The only scandal no one is telling us about is the exploitation of our stunningly truncated memories to sell us yesterday’s diet as if it were the product of today’s epiphany.

Gee, this is a pretty snarky column. But I confess, I at times catch myself thinking just this way. If we are this gullible, this biased, this myopic, and this shortsighted maybe we all just deserve to be obese and diabetic as well.

But I can’t accept that. If nothing else, I came upon a study this week indicating that cynicism increases the risk of dementia. So along with your health, I’ve got my own brain to worry about. I am attempting to avoid cynicism.

But I am indeed skeptical, and deeply worried, about our dietary doom. I worry that we are forever doomed to repeat the follies of dietary history. I worry that we will forever foreswear putting what we know to any good use, while frittering away years of life and life in years on the fruitless pursuit of nonexistent pixie dust. I worry that we are doomed to welcome back yesterday’s conspiracy theory tomorrow when we have forgotten that it isn’t new, and didn’t help us much last time. I worry we are doomed to seek out only the information that supports the view we like best, and lob insults at others doing the same with views we like less.

But I am just not willing to accept a personal doom of cynicism compounded by dementia. So I am doomed to keep trying.

David L. Katz is the founding director, Yale-Griffin Prevention Research Center. He is the author of Disease-Proof: The Remarkable Truth About What Makes Us Well.