What I used to believe
What the book is, it turns out, is a history of the evolution of our understanding of dietary fats, complete with detailed descriptions of each study which drove the scientific consensus we've seen since 1961. And something becomes clear: the scientific consensus that fat is bad is as recent and well-supported as the legal consensus that the Second Amendment protects an individual right to bear arms, and came about in pretty much the same way.
In the fifties, a charismatic man named Ancel Keys believed that dietary cholesterol, which he later switched to dietary fat and then saturated fat, caused both obesity and heart disease. He conducted a bunch of studies trying to prove this, which never actually supported his hypothesis, but he managed to Wayne LaPierre the American Heart Association, which was the major non-governmental source of funding for heart disease research. From his position at the AHA, he managed to win over other people with the money he controlled and the force of his personality, and eventually the US government, the other major source of funding for dietary research. Once that happened, studies intended to prove saturated fat was bad got funded, studies which intended to prove saturated fat was not bad didn't, and studies which accidentally proved that saturated fat was not bad got spun into suggesting it was anyways or swept under the rug.
The evidence for the idea that saturated fat was bad basically rested on three planks: First, Keys had conducted a massive epidemiological study, in which he selected countries which he expected to have low rates of fat consumption and low rates of heart disease, or high rates of fat consumption and high rates of heart disease, ignoring all the countries which evidence at the time had suggested would disconfirm his model. Despite this, he still had to engage in shitton of academically unethical behavior to get the results he wanted.
Secondly, he reasoned that it was common sense that because fat has twice the calories per unit of weight as carbohydrates and protein, people eating fat will feel less sated: fat makes you fat. Though older studies had already demonstrated that hunger is connected to insulin and fat is the only macronutrient that doesn't spike insulin, he and his followers ignored this for a conclusion that was so common sense they didn't even feel the need to test it.
Finally, studies of saturated fat consumption have fairly consistently shown that it increases cholesterol, and later showed that it increases low-density lipoproteins, a measure of the bad cholesterol, and there is also a correlation between LDL cholesterol and heart disease. Almost universally, these studies showed that diets high in polyunsaturated fats and/or carbohydrates were worse on all other health indicators measured, including resulting in low high-density cholesterol, a better marker for heart disease than high low-density cholesterol. Furthermore, epidemiological studies consistently showed that diets high in polyunsaturated fats and carbohydrates have higher rates of mortality from heart diseases, higher rates of mortality from cancer, and higher mortality overall. More recently, it was discovered that it is only a certain kind of low-density lipoprotein associated with heart disease, which stearic acid raises not at all and other saturated fats only marginally.
However the medical establishment has continued to push the "saturated fats are literally poison" narrative, despite the evidence that polyunsaturated fats and carbohydrates are worse and the fact that the entire basis of the assumption that saturated fats are bad for us has collapsed underneath them. From the wreckage of their discredited hypothesis, they soldier on, admitting that refined sugars and starch are bad for you after all, but insisting that saturated fat is still at least as bad. Based on what the author describes, the reaction of nearly every one involved in the diet science community in the US (except the handful of dissenters) has been to shrug and say that they haven't read the original studies themselves, but the science is well-established, Richard Atkins was a charlatan, and Gary Taubes is a crackpot. When they engage with dissenters at all, they engage in appeal to authority and ad hominem and the occasional red herring because their position is literally indefensible.
I think that there are several reasons that the diet science community has been so stubborn. The first is of course institutional inertia. From Richard Owen to Noam Chomsky, I've seen in plenty of other fields how one charismatic and well-respected figure can set an agenda which teaches the next generation of researchers that bad science is settled science, sending them down the wrong path. Then the people whose reputations were built on these assumptions cannot admit to being wrong.
The second is puritanism: particularly in America we tend to believe that anything enjoyable should by definition be bad for you. The third is corporate funding and lobbying. Who do you think has more clout: the big bad meat and dairy industries or the combined influence of the wheat, corn, soybean, vegetable oil, and manufactured food lobbies? The efforts of soy and vegetable oil producers in particular to vilify saturated fat and suppress research on trans fats is a disturbing trend throughout.
And the final issue, I think, is that a lot of people, especially the kinds of people who get into diet science, see compelling moral reasons to be vegetarian or vegan, whether for environmental, animal welfare, and/or animal rights reasons. They're not entirely wrong on the first two points, but one of my pet peeves is the way that vegans consistently lie about the health effects of a vegan diet, and this seems like a much more nefarious version of that. If the evidence suggests that we should probably be eating more saturated fat and protein, not less, then we need to start by acknowledging that reality and then we can have a discussion about how to do this in a manner which is humane, sustainable, and affordable for the great mass of humanity. Tricking humans into eating an unhealthy diet because misrepresenting the science will prevent the misery of animals is, to my mind, frankly evil.
So I've read this book, and I'm excited, in the sense that I am experiencing a mixture of strong emotions. I am relieved to realize that the evidence suggests that there is no reason to cut back on saturated fats, and indeed I should probably be eating more of them. I am anxious, because I'm not entirely sure where to go from here. The actual evidence suggests that a ketogenic diet is the best way for obese people to lose weight and improve their overall health. It's also the way that the only three people I know of who have achieved sustained weight loss initially lost weight. However I've stocked up a lot of whole grains, and eating a low-carb diet is expensive, and given that I don't like green vegetables, I'm worried about getting sufficient micronutrients if I cut fruit out of my diet. Do I keep doing what I'm doing (only with more saturated fats), which seems to be yielding small but steady results, or do I make the switch to a ketogenic diet in the hope of drastically improved results?
Warning: long rant
I'm furious, and I'm going to read some of the other work on this subject, but in the mean time, I cannot recommend this book to all y'all highly enough.