How many carbs to stay in ketosis

By Moira LawlerMedically Reviewed by Kelly Kennedy, RDN

August 27, 2018

By now, you’ve likely heard about the ketogenic diet, the trendy weight-loss plan that calls for dramatically reducing how many carbs you eat, moderating your protein, and upping your fat intake. As a result of following the ketogenic diet, or keto for short, for a few days, your body will enter ketosis, a state that some research links to weight loss, better glucose control, and improved cholesterol. Not all health experts would recommend the diet, though, as it can lead to kidney stones, increased intake of “bad” fats, nutrient deficiencies, decreased bone density, and stomach problems, various research suggests.

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Another big downside of keto is the fact that keeping the body in ketosis is very difficult to maintain. When following the keto diet, you’ll traditionally take in no more than 20 to 50 grams (g) of carbohydrates per day. To put that into perspective, according to the U.S. Department of Agriculture, one medium-sized pear has 27 g of carbs.

That can be a shock to the body. “One of the challenges that many people encounter when they try the ketogenic diet for the first time is the drastic lack of energy that is experienced in the first few days. This is the time when the body is learning to use fat for energy rather than readily available carbs,” says Susan Kieffer, DBA, the department chair for the School of Nursing at Purdue University Global. “You can feel very tired during this time and even a little fuzzy in your thinking.”

This experience is so common that it’s been dubbed the “keto flu.” Another reason the diet is tough to stick to? Carb cravings.

Enter keto cycling. Keto cycling involves following the keto diet for a certain amount of time and then having a day (or more) off. “It’s also called carb cycling,” says Molly Devine, RD, a Durham, North Carolina–based registered dietitian with KetoLogic, a website designed to educate people on keto. “That’s another term for it because there are higher-carb days and lower-carb days.”

The idea is to make the keto diet easier to follow. Knowing that there’s a day in the near future when you’ll be allowed to eat carbs again might help you stick to the diet for a longer amount of time.

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How Does Keto Cycling Work Exactly?

Keto cycling doesn't have a set definition. Some people choose to have five or six days on keto followed by a day or two off. Others will do keto for 10 to 12 days followed by three to four days off.

Devine typically doesn’t recommend taking more than two days off keto. She says to start with just one day so you can see how your body responds and how quickly you return to ketosis.

“If you have too many carbohydrates, you’re going to build up your glycogen stores, and it’s going to be very hard for you to get back into ketosis,” she says. She says to think about your glycogen stores, which are your body’s supply of stored carbohydrates, as a gas tank. “As long as we don’t let that tank dip over, we can deplete it pretty quickly again and get back into ketosis,” she says. “But as soon as we go beyond that three or four days [off keto], our tanks flood over and you start to actually store some of that glucose as fat, and it becomes very difficult to deplete that tank again and get back into ketosis.”

On those higher-carb days, Devine recommends sticking to healthy carbs with low amounts of sugar rather than going on a full-blown carb binge. Foods like fruit, sweet potatoes, and whole grains rather than white bread and sweets will make it easier for the body to adapt to ketosis again.

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Devine says not to jump right into keto cycling. “I would definitely not try keto cycling until you’re about two to three months into your keto diet,” she says. “That's because you need to make sure your body is fat adapted so that it can get back into ketosis easily.” In her practice, Devine has noticed that if the body is used to being in ketosis, it’ll snap back more quickly after eating a carb-heavy meal than if a person is new to keto, though there’s no firm research to support that this is always the case.

Devine says to follow up a high-carb day with vigorous exercise the next morning. The idea is to force the body to burn the glycogen you took in so it can get back to working on fat burn.

Potential Health Benefits and Risks of Keto Cycling on the Ketogenic Diet

Because keto cycling is so new, no relevant studies have examined the benefits and risks yet. Kieffer says cycling in and out of ketosis — eating carbs and then not eating carbs — could be dangerous. “If you eat a high-fat diet one day (like what is recommended in the keto diet) and then go back to eating carbs the next, I think a person could be in danger of storing much of that consumed fat, which can result in high triglycerides and cholesterol,” she says. She explains the body may not have time to convert fat to energy, so it may stick with using carbs for energy and storing fat.

On the other hand, some anecdotal evidence suggests that people are more likely to stick with keto if they incorporate cycling. You could also end up losing more weight if you stick with the diet for a longer period than you otherwise would have.

Some people believe elite athletes benefit from keto cycling because their bodies use extra carbohydrates as energy to power through difficult workouts and races. After all, research shows that following the strict keto diet impairs exercise performance. A 2017 study published in The Journal of Physiology found keto hurts athletic performance more than a high-carbohydrate diet or one that includes periods of high carbs and low carbs (which is similar to keto cycling).

It seems the body uses high-quality carbs as exercise fuel. A study published in 2018 in Nutrition Today found carbohydrates were the only macronutrient that can be broken down quickly enough for the body to use during high-intensity exercise.

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The Challenges Associated With Keto Cycling

Because it’s best to try keto cycling after your body has already adjusted to ketosis, you likely won’t be able to avoid the challenges of starting keto, such as the keto flu.

And while Devine says keto cycling can be helpful for people who crave higher-carb items from time to time, she warns it’s not for everyone.

“Anecdotally, some people who try keto cycling do find it difficult,” she says. “When you reintroduce carbohydrates back into your diet — and this is more about refined carbs, I’m not talking about eating an apple — you don’t feel very good.” She says some people experience a so-called carb hangover — the body feels kind of bloated and inflamed, and you may develop headaches.

It can also be a challenge not to overindulge on those days off the diet. “For somebody who’s been a carb addict or a sugar addict before going on the diet, all of those cravings for those sugars and those carbs come back pretty strong,” Devine says. “It’s kind of like saying, ‘I’m going to stop smoking, but I’m going to have one cigarette a month.’ Good luck.”

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Should You Try Keto Cycling?

Be careful about starting keto cycling or keto in general if you’re pregnant or nursing. Kieffer recommends these women consult their primary care provider first. People with type 2 diabetes should also consult their doctor, and those with type 1 diabetes or kidney problems should avoid the diet.

If you’ve cleared the approach with your healthcare team and weight loss is your ultimate goal, know that keto cycling won’t be nearly as effective as keto, Devine points out. “It can halt your weight loss by taking those days off because during that time you’re not going to be burning any fat and you could be putting more on,” she says. Kieffer adds that the results of keto cycling are never as dramatic as when the body is kept in a constant state of ketosis.

On the other hand, if you take the approach of following the keto diet most days but cycling helps you stay on course, cycling could help you stick to the keto diet longer.

What it boils down to is this: You need to know yourself and your self-control. “If you’re able to have a higher-carb day that includes healthy carbs and be able to get back on track the next day, then it might work for you,” Devine says. “But if you’re somebody who kind of loses control when you get around sweet foods, and one donut means the entire case of donuts, you’re going to have trouble with it.”

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