The simple and reliable advice is the same as it has been for the better part of two hundred years. It dates back at least to Jean Anthelme Brillat-Savarin in 1825 and The Physiology of Taste, which has never been out of print, an accomplishment that very few nonfiction books can claim after nearly two centuries. Brillat-Savarin got it as right as anyone. He had his own conversion experience, just as fad diet book authors typically do, and he wrote about it. He spent thirty years struggling with his weight—he called his paunch his “redoubtable enemy”—and eventually came to what he considered an acceptable standoff. He did so only after digesting the message “of more than five hundred conversations” he had held with “dinner companions who were threatened or afflicted with obesity.” In every case, he wrote, the foods they craved were breads and starches and desserts. 

As a consequence, Brillat-Savarin considered it indisputable that grains and starches were the principal cause of obesity—along with a genetic or biological predisposition to fatten easily, which not everybody has—and that sugar exacerbated the fattening process.† He lived in a time, though, when sugar was still a luxury for the wealthy, and sugary beverages were exceedingly hard to come by, at least compared to their ubiquity a century later. So he focused his advice on starches and flour, assuming that abstinence from flour would imply abstinence from sugar, since sugars back then came predominantly in baked goods, pastries, and desserts. 

Brillat-Savarin acknowledged that those who wished to reduce their weight needed something more than just the usual advice to “eat moderately” and “exercise as much as possible.” The only infallible system, he said, had to be diet, and that diet had to remove the cause of the excess body fat: 

"Of all medical prescriptions, diet is the most important, for it acts without cease day and night, waking and sleeping; it works anew at every meal, so that finally it influences each part of the individual. Now, an anti-fat diet is based on the commonest and most active cause of obesity, since, as it has already been clearly shown, it is only because of grains and starches that fatty congestion can occur, as much in man as in the animals; in regard to these latter, this effect is demonstrated every day under our very eyes, and plays a large part in the commerce of

fattened beasts for our markets, and it can be deduced, as an exact consequence, that a more or less rigid abstinence from everything that is starchy or floury will lead to the lessening of weight." 

Brillat-Savarin even went so far as to imagine his readers complaining that more or less rigid abstinence from everything that is starchy or floury meant no longer eating the foods they craved. In other words, his readers then might be much like readers now. “In a single word he [Brillat-Savarin] forbids us everything we most love,” he wrote, “those little white rolls from Limet, and Achard’s cakes, and those cookies … and a hundred other things made with flour and butter, with flour and sugar, with flour and sugar and eggs! He doesn’t even leave us potatoes, or macaroni! Who would have thought this of a lover of good food who seemed so pleasant?” Brillat-Savarin’s response was simple (although I’m bowdlerizing the translation for the more sensitive times in which we live): Then eat these foods and get fat and stay fat!

For many or most of us, this logic offers little or no escape, and as Brillat-Savarin said, the conclusion can still be deduced as an exact consequence. If carbohydrate-rich foods make us fat, then we have to deprive ourselves of the pleasure of their eating if we want to avoid this fate or possibly reverse it. But then, as Brillat-Savarin also noted, these restrictions left plenty to eat and as much of it as desired, which meant meals could be consumed that were still plenty tempting but not fattening.

Gary Taubes. The Case for Keto: Rethinking Weight Control and the Science and Practice of Low-Carb/High-Fat Eating (Kindle Locations 2519-2522). Knopf. Kindle Edition.