Keto — the diet du jour that celebs like Mick Jagger and Halle Barry are said to have tried — is an entirely new way of eating. Instead of carbohydrates making up the majority of your calories, fat takes the No. 1 spot and carbs are extremely limited when following the ketogenic diet.
“What happens when you deprive your body of carbohydrates is your body uses the fat as energy,” says Abby Langer, RD, Toronto-based founder of Abby Langer Nutrition. Eating this much fat produces ketone bodies and leads to ketosis, which means the body looks to fat rather than carbohydrates for fuel.
What’s the benefit? For a lot of people, it’s all about weight loss. “Generally, [the keto diet] ends up being low-calorie,” Langer says. “You’re eating 80 percent of your calories in fat, but it’s very filling.”
Dina Griffin, RDN, with eNRG Performance in Littleton, Colorado, says people are also drawn to the diet for the potential anticancer and anti-inflammatory benefits and the positive effect it’s been shown to have on athletic performance.
But the problem is, it’s hard to maintain ketosis, and one snack is all it takes to slip up. “Anytime you go over [about] 50 grams (g) of carbohydrates, you’re going to kick yourself out of ketosis and the weight is going to come back,” Langer says.
That’s where exogenous ketones come in.
What Are Exogenous Ketones Exactly?
The idea is when you eat something that’s not keto-friendly, you can reach for exogenous ketones to keep your body in ketosis. The word exogenous means created externally, and these supplements are forms of the ketone beta-hydroxybutyrate (BHB), which your body normally creates on its own.
“The purpose is to, in a timely fashion regardless of your dietary pattern, raise your blood level of ketone bodies,” Griffin says. Of course, your body can get back into ketosis through your diet, but that can take a few days, so exogenous ketones are designed to speed up the process.
Usually, you’ll find exogenous ketones in the form of powdered ketone salts. Less common are ketone esters, which are the purest form of ketones. Griffin says they work quickly (in 10 to 15 minutes, as opposed to an hour for the salts) and effectively, but they’re more expensive, have a more-revolting taste, and are harder to find (HVMN is one U.S. company that sells them). People also use medium-chain triglyceride (MCT) oil — or partially manmade fats — to put the body into a state of ketosis.
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Do Exogenous Ketones Work to Bring Your Body Back Into Ketosis?
Griffin says it depends on your expectations. You can’t just take them, eat a carb-heavy diet, and expect magic to happen. “The problem is a lot of people associate [using exogenous ketones] with, ‘That means I’m going to burn fat,’ and those don’t actually go together,” she says. “The ketones themselves don’t make you burn fat per se.”
Instead, they should be viewed as supplements to the keto diet. “They can enhance that state that you achieve through your dietary choices,” Griffin says. But, yes, you still have to put in the work.
Though research involving ketone supplements is still in the early stages, it seems promising. One study published in February 2018 in Obesity suggests exogenous ketone esters lower hunger hormones and act as appetite suppressors. That can lead to weight loss because “if we don’t feel hungry, gosh, we probably aren’t going to eat like we were,” Griffin says.
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Another study published in February 2018 in the Journal of Physiology found drinking a ketone ester supplement may lower blood sugar. The study was done on healthy individuals but could be helpful if similar results were found among people with type 2 diabetes.
The Potential Downsides of Using Exogenous Ketones
A serving of exogenous ketones will set you back only 100 calories or less, but most people who’ve tried them — including Langer — say they taste awful. And they’re expensive. A two-week supply could run you $50 or more. Both Griffin and Langer say that money could be better spent on whole foods.
Griffin says that because ketone salts are usually made up of ketones bound to sodium, they can be dangerous for people with high blood pressure. “There could be an issue there with heart health and heart function — that would be one concern I would have,” she says.
She also cautions that the supplements may cause stomach distress. “Some of these can really tear up our guts,” she says, adding that downing an entire serving may send you running for the bathroom. To reduce that risk, she suggests starting small — maybe one-third of a serving or one-half of a serving until your body adjusts.
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How to Pick a Good Exogenous Ketone Supplement
Because they’re so expensive, you want to make sure you pick a good one. Griffin and Langer say to ignore the companies that make these supplements sound too good to be true. Just like with any supplement, Griffin says it’s important to look at what’s in it. Beware of products with lots of fillers and instead go for one with a short, straightforward list of ingredients (Griffin likes the options from KetoSports).
The Bottom Line on Using Exogenous Ketones for Ketosis
There’s some support that exogenous ketones can be helpful for people already dutifully following the keto diet — but research has been limited. One thing we know for sure: These aren’t a get-thin-quick solution. “I think people are drawn to a quick, easy fix, kind of a magic bullet supplement, and it’s not that this won’t contribute to weight loss, but it’s not that magic bullet,” Griffin says.
Langer sums it up this way: “You have to put the effort in,” she says. “If you want to be in ketosis, do the ketogenic diet. You cannot just relax and eat whatever you want and automatically lose weight with this or any other product.”