Prosciutto, Bread, and Vegetables

Looking for a Keto Veto in a 4-Week Study

One of the very few blessings of the pandemic lockdown has been a respite from keto mania. Yes, we’ve had to blot out stupid talk about the Quarantine 15. Nonetheless, rants from true believers in ketogenic diets have been on the back burner. Interest in keto everything is down by more than half from where it was just a year ago – based on interest measured by Google Trends. But thanks to a new study from Kevin Hall and colleagues, that relative peace in the keto kingdom may not last.

Hall et al compared the effects of a plant-based, low-fat diet to those of animal-based, ketogenic diet in a highly controlled setting. The only decision facing patients was how much to eat. For two weeks on each diet, patients could eat as much or as little as they wished. The study results are something of a veto for the keto wisdom that this diet is a great way to suppress your appetite.

Better Appetite Control on the Low-Fat Diet

The pop science take on dietary patterns has held that low-carb ketogenic diets suppress a person’s appetite. tells us that “gold-standard science” proves it. The “ketogenic way of eating kills hunger and improves your mood.” On a ketogenic diet, “you’re naturally eating less simply because you’re not as hungry.”

However, this is definitely not what showed up in the results of Hall’s randomized and controlled crossover study of 20 patients. Appetite control was better on the plant-based, low-fat diet. On the other hand, the animal-based ketogenic diet yielded lower blood sugar and insulin levels.

Qualitative Differences in Body Weight

This was not a weight loss study. That’s what investigators told the participants. In fact, they instructed subjects not to do anything to change their weight during the study. But lose weight they did – on both diets. Folks lost 1.77 kilos after two weeks on the keto diet. On the low-fat diet, they lost 1.09 kilos. This was a small study, so it’s not surprising that these differences fall short of statistical significance.

However, what was different is the nature of the weight lost. On the low-fat diet, subjects lost fat mass. On the keto diet, they did not. But when you look at fat-free mass, the situation is reversed. On the keto diet, people lost fat-free mass, while they did not lose it on the low-fat diet.

Challenging Conventional Wisdom

This study of keto and low-fat diets will undoubtedly spark some heated debate because it challenges a lot of conventional wisdom. And of course, it has limitations because it’s small, short-term, and carried out in a highly-controlled setting. Its status as a pre-print tells us that it hasn’t yet been through peer review.

Nevertheless, it gives us reason to think hard about some basic assumptions. The low-carb diet was energy dense and yet it didn’t cause people to gain body fat. The low-fat diet had plenty of high-glycemic carbs to drive blood glucose and insulin levels higher. Yet it didn’t drive up hunger as the author of Always Hungry? might tell you it should. Hall et al conclude simply:

Our results suggest that regulation of energy intake and body weight are more complex than these and other simple models propose.

Click here to read the study and here for an excellent thread describing it.

Prosciutto, Bread, and Vegetables, photograph © Dejan Krsmanovic / flickr

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May 8, 2020

7 Responses to “Looking for a Keto Veto in a 4-Week Study”

  1. May 09, 2020 at 3:27 am, Just Sayin' said:

    Just thought it was worth mentioning that keto doesn’t have to be animal-based. You can follow a ketogenic diet while being vegan or vegetarian. I know that this study specifically looked at an animal-based keto diet, but after seeing how many people think it has to be animal-based, made me want to clarify for those unaware.

  2. May 09, 2020 at 11:03 am, Just Sayin' Too said:

    It can take several weeks to become fat adapted. Most studies of the ketogenic diet fail to address this. Anecdotal, but I’ve been vegan, low-fat, vegetarian, Mediterranean… None of them gave me the appetite control I experience on keto after 6 weeks. The first month was not easy, I’ll own, and I ate more calories as a result. But I kept losing weight regardless of those calories and was able to adjust them down once I was fully adapted.

  3. May 09, 2020 at 12:39 pm, Annoyed said:

    I dislike keto, my personal experience has found a very toxic community around the diet. Additionally the potential health complications surrounding poor implementation of the diet are significant.

    That said, a 20 person study proves nothing outside of participant reactions to the diets due to the tyranny of small numbers. This needs larger studies before the tone of the first paragraph is warranted.

    I do not have an easier time keeping my appetite under control on a plant based low-fat diet. I have an easier time keeping my appetite under control with low-carb or ketogenic diet. The ketogenic diet I used was primarily animal based. I had trouble eating more than 1700 calories in a day because I just wasn’t that hungry. My bad cholesterol also dropped to good levels despite how much fat/grease I was consuming. As for weight, I lost over 25 lbs in a month despite not exercising and having a very sedimentary lifestyle at the time.

    But would I recommend keto? Not without a doctor.

    • May 09, 2020 at 1:05 pm, Ted said:

      Thanks for your comment, Annoyed. Well-controlled studies, such as this one, can be very informative – as this one is. This is true even though the small size and short duration of this study are very important limitations, as we note. Hall’s study certainly won’t be the last word on ketogenic diets. But it does offer some fascinating insights.

  4. May 09, 2020 at 1:28 pm, Mary-Jo said:

    I truly appreciate this study for its rigor, methods, and execution and I’m glad Dr. Hall is taking on what are very difficult studies to do in controlled situations as to answer a question that’s been so incredibly contentious with a lot of presumptuousness circling around it. Each camp purports vehemently to assert theirs is THE ‘healthiest‘ and it can be so confusing to consumers and healthcare providers, alike, and also affects food demand and supply, often, I wonder, all to what end? Blue Zones give a lot of data that favors plant-based, so this first set of controlled setting data seems to corroborate. After having lived in 7 countries, I’ve come to observe that what affects what people eat is highly more dependent on their culture and early childhood offerings, regardless of any trending diets or prescriptive diets that come along for specific endpoints later in life.

  5. May 09, 2020 at 3:32 pm, Dave said:

    “One of the very few blessings of the pandemic lockdown has been a respite from keto mania.”

    Yeah, instead I’ve had to endure a plethora of Keto hater articles because, I suppose, you all have nothing better to do during a quarantine than find something popular to attack. If something works, and works well, it seems to draw all naysayers from their holes.

    A 2-week study for each diet? That will tell you almost nothing as to the viability of each diet. The study should have had both groups stick to each diet for at least 6 weeks.

    • May 09, 2020 at 4:31 pm, Ted said:

      Thanks, Dave, for sharing your thoughts. But if your diet is working for you, then that’s all you need. Everyone is different. Thank goodness!