What if investigative journalist Nina Teicholz told you everything you know about nutrition is wrong?

That means all the time you spent avoiding bacon, butter and red meat and eating vegetables instead, you were actually doing your body harm?

That's the counter-intuitive conclusion behind Teicholz's new book, Big Fat Surprise: Why Butter, Meat and Cheese Belong in a Healthy Diet. Despite the title and subject matter, though, this isn't a diet book and there's not a recipe to be found.

Instead, this is a frustrating tale of how junk science led the American Heart Association and later the U.S. Department of Agriculture to advocate a diet that was lower in fat and higher in carbohydrates. We listened: Since 1980, when the USDA issued its guidelines, Americans' fat consumption has fallen by 14% while our overall consumption of fat has dropped 5%.

See also: 7 Digital Diet Solutions to Help You Lose Weight

In those ensuing 34 years, U.S. obesity rates have skyrocketed.

Are those two related? Teicholz, like science reporter Gary Taubes before her, makes a case that they are. Simply put, eating more carbohydrates makes us fatter. Eating saturated fat is good for you. So put down that oatmeal and grab a plate of eggs and bacon.

Teicholz discussed her argument with Mashable. Here are some excerpts:

Mashable: It seems like you attribute much of the popularity of low-fat, high-carbohydrate diets to one man: Ancel Keys.

Nina Teicholz: I think he got the ball rolling on this saturated fat hypothesis. It would be far too simplistic to say that he's the sole reason why we now believe that saturated fat causes heart disease. It was really when it was institutionalized in the American Heart Association and the National Institute of Health that it became this ocean liner that could not change course [...] I think of institutional science as an oxymoron because scientists have to be skeptical and questioning and institutions have to be constant and not flip-flop, and it's very hard to change course when you have embraced one idea.

Mashable: I had looked at American Heart Association as sort of a benign organization, but in your book you point out that it takes corporate funding, which leads to conflicts of interest.

NT: Procter & Gamble really launched the American Heart Association as a national organization. It had previously been a small, underfunded professional cardiologists' society that was really struggling for money. And Procter & Gamble, which sponsored this radio show, made it the beneficiary of that radio show. Virtually overnight, $1.7 million flowed to their coffers, and they were suddenly a powerhouse. At the time, one of Procter & Gamble's biggest products was Crisco oil and the American Heart Association coincidentally was embracing vegetable oils, unsaturated fats, to replace saturated fats. I just want to say that I do believe that everyone who was involved in the AHA in those crucial years in the late '50s and early '60s genuinely believed that they had the solution to the heart disease epidemic. They just jumped the gun on the science.

Mashable: OK, let's jump into your thesis: For the layman, why are carbohydrates bad for you in excess?

NT: Carbohydrates break down into two things in the bloodstream: glucose and fructose. I'll give you an example: table sugar breaks down into half glucose, half fructose. Glucose triggers the release of insulin in your bloodstream, which is the king of all hormones for socking away fat on your body. And fructose wreaks havoc with your cholesterol levels. So, the combination of them is unhealthy. If you are chronically exposed to them you will become insulin-resistant and you will become fat and you'll be at higher risk for heart disease.

Mashable: So is fruit bad for you? What about vegetables?

NT: I think too much fruit is probably not a good idea. Fruits have also been bred over the last century to be much sweeter. There are also some fruits that are much higher in sugar than others like pineapple, watermelon are higher in sugar than blueberries. Certain vegetables are very starchy and that starch breaks down to glucose. So potatoes, root vegetables, those are fairly starchy vegetables. My takeaway is that just because of the USDA guidelines, we've shifted too far in the carbohydrate direction. We eat 25% more carbohydrates that we did 30 years and that's too much.

Mashable: Throughout the book you call various health advocates to task for cherry-picking data to make their case. Couldn't the same charge be levied at you?

NT: I think it's pretty clear in my book that I go through all the studies. The reason this book took me so long is that I read through all the literature and the literature often contradicted what I came to believe was true. I also came to this topic with no preconceived notions. I was a vegetarian, and I was hard to convince. It took me a long time of reckoning with the actual data to come to believe what I did.

Mashable: Is there any mention of the China Study, which makes a strong case for a vegan diet, in the book? I didn't see it.

NT: It's in a footnote. There are two reasons: One, it never appeared in a peer-reviewed journal. It appeared in a corporate-sponsored supplement. The other thing is, it's an epidemiological study. Epidemiological studies, as I go on ad naseam about in my book show association, but not causation. They just don't. No matter how big they are, they don't show causation.

Mashable: What about Colin Campbell, the author of the China Study book? He claims that heart attack patients have been restored to health with a vegan diet? How do you explain that in light of your counter-thesis?

NT: I have a two-part answer to that: One, anecdotal evidence is not a substitute for science. It's not that I don't believe him, it's just that it can't be used as evidence. The other part of that is all diets work to a certain extent because when you go on a diet, everybody cuts back on desserts. So everyone is cutting back on sugar. That's why all diets work to some extent.

Mashable: So, is the takeaway that you can eat as much bacon, butter and steak as you want?

NT: It sounds extreme when you put it that way. What the science really shows is that a high-fat diet is healthier than a low-fat diet. So the takeaway for me is that it's fine as part of that high-fat diet to eat meat, cheese, milk and eggs. I think if 40% of your diet is fat, that's fine.

Mashable: What about someone who is a vegetarian for ethical reasons? Are they harming their health?

NT: I think it's hard to stay healthy as a vegan. In animal experiments that were done in the '20s and '30s when the question was what's the best diet for reproduction — this was before nutrition science took a huge turn-off to looking at heart disease — what they found was it was very hard to keep animals healthy on a strictly vegan diet. It's not impossible, but the balance of grains and seeds and legumes that you have to employ is hard to attain. And the addition of whole milk or butter almost immediately helped any growth faltering. So I think it's perfectly possible to stay healthy with dairy and eggs. That seems like a perfectly feasible solution.

Mashable: So sugar is bad for you? What about alcohol?

NT: I don't know the whole scientific literature on alcohol. I don't want to know because I love red wine.