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Chances are, you’ve read about or know someone who’s on the keto diet, or perhaps you’ve experimented with it yourself. Short for “ketogenic,” the keto diet is an extremely low-carbohydrate eating plan that sends the body into ketosis—a state of burning fat for energy, rather than sugars.
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People on a ketogenic diet consume 50 grams or fewer of carbohydrates per day and instead eat higher-than-normal amounts of fat and protein. And while they often lose weight quickly, health experts say the diet isn’t sustainable—and often isn’t healthy—to follow for long periods of time.
That’s where keto cycling comes in: Touted as a less restrictive, more sustainable way to get the benefits of a ketogenic lifestyle, keto cycling involves following a ketogenic diet for a few days in a row, then taking a break and eating high (or at least normal) levels of carbohydrates for a day. In other words, it’s the best of both worlds... right?
Well, as with most things science and dieting and weight loss, it’s not quite that simple. We checked in with two nutritionists—each with a difference stance on the keto diet in general—to find out what they think about this on-again, off-again approach. Here’s what you should know before giving it a try.
What is keto cycling?
Because keto cycling isn’t a branded or trademarked term, there’s no exact definition for how it’s done. Some websites describe following a strict keto diet for six days a week followed by one “cheat day” or “high-carb day.” Others encourage switching it up more frequently.
Josh Axe, a doctor of natural medicine and clinical nutritionist, says his preferred method of keto cycling is a two-day-on, one-day-off pattern. Axe is a big proponent of the keto diet, and he sells keto-related supplements on his website. But because the diet is difficult to follow long-term, he believes it should ideally be done for just 30 to 90 days.
“After that, it’s a good idea to transition into another diet that’s going to be easier to maintain, and maybe that’s keto cycling,” says Axe. He says he was turned onto the benefits of keto cycling by his wife, who tried it herself after doing the keto diet for 30 days.
“She started eating like that, two keto days and one carb day, and she noticed results probably just as good as doing the full-on keto,” he says. “Her hormones really balanced out, she lost about 10 pounds, and we found she was able to do this long-term rather than crashing and burning the way people sometimes do on long-term diets.”
Carb cycling vs. keto cycling
Axe describes keto cycling as “the keto diet meets carb cycling.” So what’s the difference between the two terms? Carb cycling is a more general term used when a person cuts back on carbs for a few days (followed by a high- or moderate-carb day), but does not restrict so much that the body has to switch to burning fat for fuel.
“The ratios are slightly different,” says Axe. “Carb cycling tends to be more high-protein, moderate-fat, and you’re not really ever getting into ketosis. Keto cycling is higher-fat, higher-protein, and lower-carb than what you’d eat if you were carb cycling.” In both carb cycling and keto cycling, he adds, people may choose to match up their carb days with high-intensity workout days.
During keto cycling, the body goes in and out of ketosis depending on what fuel—fat or carbohydrates—is available for burning. “Our hunter-gatherer ancestors weren’t concerned with carb cycling," says Axe, "but when you think about it, sometimes they were eating quite a few carbs and sometimes they were eating fat because of the natural fluctuation in food sources.”
Keto cycling benefits
Some proponents of keto cycling say that an on-again, off-again plan can help prevent side effects of a full-on keto diet. Theoretically, fatigue, nausea, diarrhea, and other symptoms of “keto flu” may be lessened if people aren’t in ketosis for so many days at once. There’s also some concern that carbohydrate restriction over a long period of time may negatively affect hormones, cholesterol levels, or even people's moods. Again, theoretically, these problems might be avoided with regular carb-replenishment days.
Because there are no published studies on keto cycling versus a regular ketogenic diet, however, no one can definitively say what the health benefits are of one over the other. But one thing is for sure, says Axe: Mentally, keto cycling can be much easier to stick with in the long run, and it allows for more variety in the diet—something most health experts would agree is a good thing for physical health, as well.
Axe generally recommends keto cycling as a way to continue the ketogenic diet after an initial 30- to 90-day period of everyday carb-restriction. “But the truth is,” he says, “somebody can just do keto cycling and can still really see results, even without doing full-on keto.
Keto cycling negatives
Kristen Kizer, RD, a dietitian at Houston Methodist Medical Center, says she advises her clients to avoid the keto diet. She says it’s unbalanced and restricts too many important food groups—and while people do lose weight, she says, they almost always gain it back once they add carbs back into their diet.
But that doesn’t mean she thinks keto cycling is any better. She’s concerned that the keto diet can promote disordered eating and that keto cycling especially can lead to binge behaviors. “A lot of people will think, 'All I need to do is be very low-carb for five or six days, then on my cheat days I can eat as many carbohydrates as I want,'” she says. “It definitely is not supposed to work that way.”
Keto cycling is also likely to make people’s weight fluctuate, especially if they are just coming out of several weeks or months of full-on carb restriction. “It doesn’t establish a healthy relationship with food, and it can mentally throw people off if they regain all the weight they just lost,” says Kizer.
Kizer also points out that ketosis is an altered metabolic state, and, unlike Axe, she worries that it’s unhealthy to force the body in and out of it on a regular basis.
“People can fall in and out of ketosis, and they won’t really know where they are unless they’re monitoring their ketones,” she says, referring to acids in the blood that are produced as a result of fat-burning. “You can’t just take a break for a day and then pick up where you left off after eating pancakes and waffles.”
In fact, Kizer says she’d prefer that people follow a full-on ketogenic diet than keto cycling. “Again, I’d really prefer they do neither,” she says, “but I just feel there’s a lot more room for error when you start talking about cycling your carbs.”
What to eat when keto cycling
If there’s one thing that Axe and Kizer agree on, it’s that there is a healthy way and an unhealthy way to incorporate carbohydrates in your diet. “Keto cycling doesn’t mean going completely off the wagon and eating pizza and a bag of chips and a tub of ice cream,” says Axe. “What you want is those good carbs we’d always recommend as part of a balanced diet—brown rice, quinoa, sweet potatoes, fruit in the morning, that type of thing.”
Some of Axe’s favorite foods to recommend on carb days include açai bowls, berry smoothies with protein powder, sweet potato fries (alongside a grass-fed burger with a gluten-free bun, he says), pizza with cauliflower crust topped with chicken and buffalo mozzarella cheese, and “a little dark chocolate” for dessert. He suggests getting 30 to 40% of your food intake on these days from healthy starches and carbohydrates, versus just 5 to 10% on keto days.
Kizer says that regardless of carb cycling, ketosis, or any other diet that people may be trying, it’s always smart to choose carbohydrates that are as whole and unprocessed as possible. “I’m talking about whole fruit—not an apple strudel, but real apples,” she says. “I’m talking about brown rice, potatoes, beans, corn, and whole grains like quinoa, amaranth, and farro.”
“I try to have my clients focus on food being as less processed as possible and avoid things like white rice, white bread, and sugary cereals,” Kizer says. “Unfortunately, a lot of people are choosing things like muffins, French toast, or garlic bread on their ‘days off,’ and they’re using keto cycling or carb cycling as an excuse."
This article originally appeared on Health.com.