The high-fat keto diet has become popular among people looking to rid their bodies of harmful chemicals.


In a new post on her app, Kourtney Kardashian talks about the few months she spent following the keto diet, which she described as a "really positive experience." The mom of three said her doctor recommended going keto “to help a metal detox," which made us wonder: Is there any research behind that advice?

Versions of the keto diet—short for ketosis or ketogenic—have been around for years: It's a high-fat, low-carbohydrate eating plan, with roughly 75% to 90% of daily calories coming from fat and only about 2% to 5% coming from carbs. (The remaining 6% to 20% comes from protein.) It also involves periods of intermittent fasting; on Kardashian’s plan, that meant not eating for 14 to 16 hours after dinner and abstaining for a full 24 hours once a week.

Essentially, the idea behind the diet is to kick the body into a sort of starvation mode—ketosis—during which it burns fat rather than glucose. It was originally used to treat patients with epilepsy, because the diet seems to have an effect on neurons in the brain, and can sometimes reduce seizures.

In the last few years, interest in the diet as a potential therapy for people with diabetes and insulin resistance has grown. It’s also become popular among people who are simply looking to lose weight or—like Kardashian—rid their bodies of toxic chemicals.

So is there truth to the rumors about this so-called miracle diet? Riley Thornton, RD, a nutritionist at the University of Alabama at Birmingham, says that some people may lose weight on a ketogenic diet because it restricts carbohydrate intake. “But if you’re replacing them with a lot of fats, it may not be helpful,” she says. “And if you’re eating a lot of saturated fat, specifically, it could be detrimental to your heart health.”

In her article, Kardashian says that she ate “minimal carbs,” learned to get creative with substitutes like cauliflower rice and spaghetti squash, and ate more fresh vegetables and lean protein. And those are smart steps, especially since most of us could stand to eat fewer refined carbohydrates (like white bread and pasta) and more leafy greens.

But Kardashian also says that she ate “no grains, beans or legumes,” which means cutting out entire food groups that provide important nutrients, like fiber. Her post doesn’t mention fruit (besides avocado and banana smoothies), but Thorton says that’s another food group that tends to be restricted or eliminated in ketogenic diets because it’s high in carbohydrates.

But back to the detox angle: Kardashian wrote in another post last year that her doctor “found that I had high levels of metals like mercury and lead, so my motivation for this detox is to get rid of the metals in my system.” But according to Thorton, there isn't any research to suggest that a high-fat, low-carb diet can lower the levels of heavy metals in the body. “I’d never heard of that before today,” she says.

David Ludwig, MD, co-director of the New Balance Foundation Obesity Prevention Center at Boston Children’s Hospital, says that ongoing research around the ketogenic diet is exciting, especially in the areas of obesity and type 2 diabetes. (He is leading up some of that research himself.) “But we still lack definitive data on a lot of basic questions,” he says.

As for the idea that it could help remove impurities from the body, he adds, “there are theoretical reasons why a ketogenic diet could help detoxification systems—but it’s still speculative; there’s no significant evidence for it yet.” There’s also no reason to think a ketogenic diet alone would affect concentrations of mercury or lead in the body, he says.

According to the Centers for Disease Control and Prevention, the best ways to lower lead levels in the body are to eliminate sources of exposure (like old paint in homes built before 1978), and to eat healthy foods with calcium, iron, and Vitamin C—nutrients that “may help keep lead out of the body."

To lower mercury levels, Dr. Ludwig recommend avoiding fish that tend to have high concentrations, such as swordfish, tuna, and shark. But don’t ditch seafood entirely just because you’re worried about mercury exposure: Fish can be an important source of lean protein and healthy fat, and there are plenty of low-mercury options.

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The bottom line, says Thornton, is that any type of unconventional diet that claims to rid the body of toxins is worth being skeptical about. “The body is already quite good at excreting toxins in urine and in the stool,” she says. “So for any kind of detoxification, I will always recommend an overall healthful eating plan, with plenty of fluids and plenty of fiber to promote regular trips to the bathroom.”

Kardashian wrote in her post that while the keto diet was an overall positive experience for her, it occasionally caused headaches and low energy. She also acknowledges that it’s “a more restrictive plan than average diets,” and encourages readers to check with their doctors before trying it themselves.

Thornton agrees that, for most people looking to maintain healthy eating habits long-term, extreme plans like the keto diet aren’t the way to go. “It’s best to follow a more sustainable eating pattern that fits your own lifestyle,” she says.