Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

The new data is said to debunk “some, if not all, of the popular claims made for extreme carbohydrate restriction.” But what about ketones suppressing your hunger? In the tightly-controlled metabolic ward study where the ketogenic diet made things worse, everyone was made to eat the same number of calories. So yes, eat the same number of calories on a keto diet, and lose less body fat, but out in the real world, maybe all those ketones would spoil your appetite enough that you’d end up eating significantly less overall. On a low-carb diet, people ended up storing 300 more calories of fat every day. But outside the laboratory, if you were in a state of ketosis, maybe you could offset that if you were able to sustainably eat significantly less.

Paradoxically, people may experience less hunger on a total fast compared to an extremely low-calorie diet. This may be thanks to ketones; in this state of ketosis, when you have high levels of ketones in your bloodstream, your hunger is dampened. How do we know it’s the ketones? Because if you inject ketones straight into people’s veins, even those who are not fasting lose their appetite, sometimes even to the point of getting nauseated and vomiting. So, ketones can explain why after a few days you might feel hungrier on a low-calorie diet than on a total zero-calorie diet (a fast).

Can we then exploit the appetite-suppressing effects of ketosis by eating a ketogenic diet? If you ate so few carbs to sustain brain function, couldn’t you trick your body into thinking you’re fasting, and get your liver to start pumping out ketones? Sure! But is it safe, and is it effective?

A meta-analysis of 48 randomized trials of various branded diets found that those advised to eat low-carb diets and those told to eat low-fat diets lost nearly identical amounts of weight after a year. Now obviously, “high attrition rates and poor [dietary] adherence” complicate comparisons of efficacy—I mean, they weren’t actually put on these diets; they were just told to eat that way. But you can see how even just moving in each respective direction can get rid of a lot of CRAP, which is Jeff Novick’s beloved acronym for Calorie-Rich And Processed foods. After all, the four largest calorie contributors in the American diet are refined grains, added fats, meat, and added sugars. Low-carb diets cut down on 1 and 4, and low-fat diets tend to cut down on 2 and 3. So they both tell people to cut down on doughnuts. Any diet that does that already has a leg up.

I figure a don’t-eat-anything-that-starts-with-the-letter-D diet could also successfully cause weight loss if it caused people to cut down on doughnuts, danishes, and Doritos—even if makes no nutritional sense to exclude something like dill.

The secret to long-term weight loss success on any diet is compliance. Diet adherence is difficult, though, because any time you try to cut calories, your body ramps up your appetite to try to compensate. This is why traditional weight-loss approaches, like portion control, tend to fail. For long-term success, measured not in weeks or months but in years and decades, this day-to-day hunger problem must be overcome. On a wholesome plant-based diet, this can be accomplished thanks in part to calorie density—you’re just eating so much food. On a ketogenic diet, it may be accomplished with ketosis.

In a systematic review and meta-analysis entitled “Do ketogenic diets really suppress appetite?” the answer, they found, was yes. Also, ketogenic diets offer the unique advantage of being able to track dietary compliance in real time with ketone test strips you can pee on to see if you’re still in ketosis. There’s no pee stick that will tell you if you’re eating enough fruits and veggies. All you have is the bathroom scale.

Keto compliance may be more in theory than practice, though. Even in studies where ketogenic diets are being used to control seizures, after a few months dietary compliance may drop to under 50 percent. This can be tragic for those with intractable epilepsy, but for everyone else, the difficulty in sticking to ketogenic diets long-term may actually be a lifesaver. I’ll talk about keto diet safety next.

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