The keto diet and intermittent fasting (IF) are two popular diets for losing fat, gaining lean muscle mass, and boosting your energy levels. But could combining these two methods help you experience even greater results? In short, the answer is yes. Fasting on the keto diet is a simple hack that can accelerate your results and could provide even greater health benefits than just doing keto alone.
Before we get into the how’s and why’s of intermittent fasting on the keto diet, here’s a quick rundown on what intermittent fasting is.
What is Intermittent Fasting?
If you’ve slept for 12 hours straight, you’ve practiced intermittent fasting without even realizing it. Intermittent fasting simply means that you go a certain period of time without eating — between 12 to 48 hours, to be exact — which is called a fasting window. However, when it comes to practicing intermittent fasting for specific health benefits, there’s some strategy to it, which is why it’s important for you to know the difference between the fed and fasted states.
The Fed State vs. Fasted State
When you eat every few hours, you’re in a “fed” state, which is when your body is busy digesting, absorbing, and assimilating the nutrients from your meals. Most of us remain in this state during the day, aside from when we’re sleeping. Fat burning isn’t a priority here.
The reason why intermittent fasting can provide certain health benefits for weight loss is because it allows your body to enter the fasted state. Without an intake of nutrients and other extra work for your body to do, accelerated fat burning can now take place (1).
5 Key Benefits of Intermittent Fasting on the Keto Diet
#1. Entering Ketosis Sooner
As Perfect Keto explains, “since the keto diet is designed to force the body into running on ketones from a very low carb intake, you’re already “fasting” yourself of carbs and glucose. This mimics the actual fasting that takes place with intermittent fasting.”
In other words, since you’re already restricting your body’s primary fuel source on the keto diet, adding a fasting window can kickstart your body into ketosis sooner. As an added bonus, you may find it easier to fast for longer periods of time, since you’ve already had a brief intro to fasting on the keto diet. In fact, some sources suggest intermittent fasting on the keto diet may help eliminate symptoms of the keto flu.
#2. Accelerating Weight Loss
The keto diet works for breaking weight loss plateaus in a number of ways. First, it helps you burn fat for energy instead of carbs, which manipulates your metabolism to burn stored fat quicker. A high-fat diet also is more satiating because fats take longer to digest than any other nutrient. This helps prevent unnecessary snacking and extra caloric intake throughout the day.
Combining the keto diet with intermittent fasting creates an even smaller eating window, which allows your body to use the food you’re eating purely as fuel, without feeling hungry or deprived.
#3. Balancing Blood Sugar
Both intermittent fasting and the keto diet have been shown to improve insulin sensitivity and balance blood sugar levels, which is crucial for weight loss — especially around the midsection (2). Since both diets have the ability to stabilize blood sugar levels, taking a combined approach may be helpful for those with type 2 diabetes (3)(4).
Stable blood sugar levels also help eliminate brain fog, as well as improve focus, concentration, and memory (5).
#4. Improving Nutrient Absorption
One study showed that carb and protein absorption was more efficient in those who did fasted cardio before eating a meal, compared with those who had a carb-rich breakfast before working out (6). This suggests that fasting can help your body use nutrients from your post-workout meals more efficiently, which may accelerate the growth of lean muscle mass (and improve your health in general).
#5. Promoting Natural Detoxification
Both intermittent fasting and the keto diet trigger a natural process in the body called autophagy (7)(8). Autophagy literally means “self-eating.” While this may sound terrifying at first, autophagy is like your body’s inner housekeeping system to remove, detoxify, and rebuild healthier cells.
Autophagy happens naturally during periods of fasting, or when your protein and carb intake is low. Combining both methods can help accelerate this process, which may reduce your risk for cardiovascular disease and type 2 diabetes.
How to Fast on the Keto Diet
As we covered above, there are several intermittent fasting methods you can try, with no method being right or wrong. The rule of thumb for anyone practicing intermittent fasting is to fast for a minimum of 12 hours, and no longer than 48 hours at a time.
The best way to tell which fasting window works for you, and how often to fast, is to simply pay attention to how you feel. Take note of your energy levels, hunger levels, cognitive function, and sleep quality.
If you find that you’re starving throughout the day, or can barely make it through a workout when you’re fasting, you may need to shorten your fasting window, then gradually increase it by one hour each week. Alternatively, you could reduce your fasting days. It’s also important to make sure that you are consuming enough calories during your feeding window. Working with a healthcare professional, such as a nutritionist or dietician, can help you determine the specifics of exactly how many calories you need per day, based on your unique body composition, activity level, and any other lifestyle factors.
In short, you can incorporate intermittent fasting on a keto diet, just like you could on any other diet (such as the Paleo diet) — the same rules apply. However, the key benefit to intermittent fasting on the keto diet is that it may help kickstart ketosis and help you reach your health goals sooner.
Here are a few sample schedules to get you started:
- Eat from 9am-9pm, then fast for 12 hours.
- Eat from 9am-7pm, then fast for 14 hours.
- Eat from 12-8 pm, then fast for 16 hours (also known as the 16/8 method).
Who Shouldn’t Practice Intermittent Fasting on a Keto Diet?
Combining the keto diet and intermittent fasting may not be a good fit for everyone. We recommend you do not practice intermittent fasting if you are:
- Under chronic stress
- Have a history of disordered eating, such as anorexia or bulimia
- Struggle with sleep disorders, or have difficulty sleeping
While combining intermittent fasting with the keto diet can help you achieve your health goals quicker, it’s important to keep in mind that both diets are meant to be practiced as part of a healthy lifestyle. Few things can replace a diet rich in whole, nutrient dense foods.
If you’re just starting out on the keto diet, it’s a good idea to give your body at least 3 to 4 weeks to adjust before adding periods of intermittent fasting to the mix.