Should You Pair Keto With Intermittent Fasting?

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by Dr. Joshua Axe, D.N.M., D.C., C.N.S.
Perhaps the two hottest diet trends on the face of the planet right now are keto and intermittent fasting. But should you be doing the two of them together? In a word, yes. Here’s your guide to combining the powers of a ketogenic diet and intermittent fasting.

First, A Keto Refresher​

As you probably know by now, the ketogenic diet is a very low-carb, very high-fat diet that switches your body into a state called ‘ketosis.’ In this state you use fat (in a form called ketones) for fuel instead of the usual glucose from carbs.
To enter into ketosis, you typically need to eat about 75 to 80 percent of your daily calories from fat. From there, you’ll eat about 20 percent of your calories from protein, and just about five from carbs. Though it’s long been used for conditions like epilepsy, the ketogenic diet has recently gained popularity for its ability to support weight loss. Researchers are also now exploring its potential benefits for those with metabolic conditions like diabetes and neurological diseases like Alzheimer’s, too.
When they enter ketosis and use fat (body fat, included) for energy, many people experience reduced appetite and cravings. They’re also able to comfortably go for longer periods of time without eating. That’s where intermittent fasting comes in.

Intermittent Fasting Basics​

Fasting, which involves going extended periods of time without food, dates back thousands of years, to the times of Socrates and Plato. In fact, a number of religions across the globe incorporate the ritual of fasting, and believe it offers both spiritual and health benefits.
These days, various forms of fasting have gone mainstream—perhaps the most well-known of which is intermittent fasting (IMF). In intermittent fasting, you cycle between periods of fasting and eating.
Here are a few common approaches:

• Time-restricted eating, in which you only eat within a certain window of time—usually eight hours or less—each day.
• Alternate-day fasting, in which you reduce total calorie intake to about 500 calories or less on a few nonconsecutive days per week.
• Whole-day fasting, in which you completely fast one or two days a week.

Intermittent fasting forces your body to use up all of its available energy (glucose stored as glycogen in your muscles and liver) and start utilizing stored body fat instead.
According to the Harvard School of Public Health, cycling between periods of normal caloric intake with periods of no intake supports weight loss better than prolonged, constant dieting, because it doesn’t decrease your overall calories needs.

So, Why Combine Keto And Intermittent Fasting?​

Because of keto and intermittent fasting’s weight-loss benefits, you can see why they make an appealing pair. I often recommend intermittent fasting to people already following a keto diet who are looking to amplify their results.
Here are some of the weight loss-related perks the pairing offers:

• Improved glucose regulation (which decreases insulin production and fat storage)
• Increased ketone production (more fat fuel!)
• Increased leptin (the satiety-signaling hormone) production and decreased leptin resistance
• Reduced hunger levels
• Better craving control
• Improved ability to read hunger and fullness signals

Though weight loss may be what’s made keto and intermittent fasting famous recently, it’s far from their only benefit. In fact, the combo can have a number of other powerful effects on health, such as:

• Improved blood pressure and cholesterol levels
• Improved metabolic health
• Reduced markers of inflammation
• Enhanced neurological and cognitive health
• Improved detoxification (fasting redirects energy from digestion towards repair and cleansing)
• Potential reduced risk of certain types of cancer, including breast or colon cancer

Plus, in animal studies, calorie restriction has also been shown to promote longevity and increase lifespan—though research has yet to explore this benefit in humans.
Ultimately, the combo of a ketogenic diet and intermittent fasting offer potential benefits for anyone struggling with their weight, metabolic health, or inflammation-related conditions. (Talk to your doctor if you have a history of eating disorders, kidney, gallbladder or liver disease, or diabetes, though.)

Getting Started With Keto And Intermittent Fasting​

Interested in trying keto and intermittent fasting for yourself? Since both strategies require making significant changes to your daily routine, keep the following guidelines in mind:

• Make sure to fill your diet with healthy, whole, high-healthy-fat foods. Since you’ll ultimately be eating less often (and likely less overall), it’s crucial that your meals contain as many nutrients as possible. Keep your fat intake high to ensure you get enough calories, and don’t skimp on fiber– and nutrient-rich non-starchy veggies!
• To avoid feeling overwhelmed, start with either keto or intermittent fasting first. Once you feel comfortable with that (after, say, three to six weeks), you can start to experiment with adding the other.
• If you’re new to fasting, aim to fast for about 13 hours a day and include the overnight hours in your fast. If you get the recommended seven to nine hours of sleep per night, you’ll knock out more than half your fast while you sleep. As you get comfortable, you can gradually increase your daily fasting window up to about 16 hours per day.

What A Day Of Keto And Intermittent Fasting Might Look Like​

A day of keto and intermittent fasting truly starts at night: You might eat a keto-approved dinner (something like a grass-fed burger with avocado and salad) around six o’clock, and then abstain from eating until anywhere between seven in the morning and noon the next day.
Related: Want To Try Keto? Here’s What A Healthy Day Of Eating Fat Looks Like
While you’ll avoid all solid foods during your fast, you can still drink water, black coffee, and tea. When you do eat, keep your meals very high in fat, moderate in protein, and very low in carbs.
Though snacking is allowed, you may not need more than two meals a day, along with coffee or tea between meals, as your appetite decreases. If you’re active or dealing with adrenal issues and need to snack, though, I like hard-boiled eggs, half an avocado with raw veggies, nuts, or a keto smoothie.

Mistakes To Avoid​

When it comes to keto, it’s important to remember that eating high-fat and eliminating carbs is not supposed to be a permanent change. Though there’s not much research about the impact of staying in ketosis long-term, some suggest it could increase risk for kidney stones, osteoporosis, high cholesterol and liver issues. That’s why I typically recommend that dieters stay in ketosis for three to six months, and reintroduce carbs on certain days from there.
And when it comes to fasting, remember that you don’t have to fast every single day to experience the benefits. In fact, forcing yourself to fast every day could leave you burnt out, fatigued, or irritable. Focus first on sticking to eating keto and try to incorporate fasting about three days per week from there. A little flexibility will make a keto lifestyle and intermittent fasting more sustainable long-term.
Lastly, remember to always listen to your body. If you feel sluggish, weak or fatigued at any point, don’t ignore your body’s signals. Try increasing your calorie and carb intake a bit and consider cutting back on how many days a week you fast.

Dr. Josh Axe, D.N.M., D.C., C.N.S., is a doctor of natural medicine, clinical nutritionist, author, and member of The Vitamin Shoppe’s Wellness Council. Dr. Axe operates one of the world’s largest natural health websites, sharing healthy recipes, herbal remedies, nutrition and fitness advice, and information on essential oils and natural supplements. Dr. Axe founded one of the largest functional medicine clinics in the world, in Nashville, TN, and has served as a physician for many professional athletes.