Intermittent fasting and the ketogenic diet are two of the top trending eating patterns among dieters and health enthusiasts alike. However, while there are plenty of differences between intermittent fasting vs. keto, they can actually be combined to help amplify results and reach ketosis even faster. In fact, by practicing intermittent fasting on keto, you can take advantage of the unique benefits that both have to offer.
So should I fast on keto? What ingredients belong on the keto diet food list? And how many hours should you fast intermittently? Here’s everything you need to know about intermittent fasting on keto, plus how to get started.
Related: Beginner’s Guide to the Keto Diet
Why Is Intermittent Fasting on Keto Recommended?
Intermittent fasting is a technique that involves restricting your food intake to a certain time window each day and then fasting for a specific period. There are several different fasting methods, with many variations that can fit nearly any personal preference or routine. A few of the most common types of intermittent fasting include alternate day fasting, 16/8 fasting and the 5:2 diet, each of which varies based on the amount of time you spend fasting during the week.
Fasting on keto can be incredibly beneficial, especially if you’ve reached a plateau and aren’t seeing results from the ketogenic diet alone. While it’s not required, keto intermittent fasting can bring the benefits of your diet to the next level and help optimize your health. It is also thought to speed up ketosis by helping your body burn through glycogen stores more quickly, which can help sidestep symptoms of the keto flu to get faster results.
There are plenty of keto and intermittent fasting success stories out there, and several reasons you may want to consider adding it to your routine. In particular, keto fasting has been associated with several benefits, including:
- Improved Heart Health: According to a study published in PLoS One, fasting is effective at improving cholesterol levels, which could potentially help reduce the risk of heart disease.
- Increased Weight Loss: Studies show that fasting can reduce body weight and body fat while also helping to retain muscle mass to improve body composition.
- Better Blood Sugar Control: Not only can fasting decrease levels of blood sugar, but it can also increase insulin sensitivity to help your body use insulin more efficiently.
- Decreased Inflammation: Several studies have found that fasting may reduce several markers of inflammation, which is thought to play a central role in health and immune function.
- Reduces Hunger: Intermittent fasting keto could decrease levels of leptin, the satiety hormone that signals your brain when it’s time to stop eating. Keeping leptin levels low can help prevent leptin resistance to help keep hunger and appetite under control.
- Promotes Brain Function: Animal studies show that fasting can improve cognitive function and preserve brain health by influencing specific proteins involved in brain aging.
How to Intermittent Fast on Keto
By now, you may be wondering: how can I do keto and intermittent fasting? By following just a few simple steps, it’s easy to get started and set yourself up for success.
1. Pick Your Protocol
There are several different fasting protocols, making it easy to find a method that works for you. To get started, simply pick a protocol fits into your daily routine and jump right in. Here are a few of the most common methods:
- Alternate-Day Fasting: This type of eating pattern involves fasting every other day. On fasting days, you can either abstain from eating altogether or limit your intake to around 500 calories per day. On non-fasting days, you should follow a healthy keto diet as usual.
- 16/8 Fasting: The 16/8 intermittent fasting ketosis plan consists of fasting for 16 hours per day and limiting your food intake to just 8 hours daily. This generally involves not eating anything after dinner and skipping breakfast the following morning.
- 5:2 Diet: On this plan, you follow a standard keto diet for five days out of the week and restrict intake to around 500–600 calories for the remaining two days.
- 23/1 Intermittent Fasting Keto: With this method of intermittent fasting, you should limit food intake to just one hour per day and fast for the other 23 hours of the day.
2. Calculate Your Keto Macros
After determining your preferred protocol of intermittent fasting, you should start planning out your diet for the days that you do eat. On a standard keto diet, 75 percent of total calories should come from fat, 20 percent should be from protein and 5 percent should come from carbs. When getting started, however, you can start with a modified keto diet instead, which is often considered more flexible and easy-to-follow. With this diet plan, about 40–60 percent of calories should come from healthy keto fats with 20–30 percent from protein foods and 15–25 percent from carbohydrates.
There are plenty of online calculators that can help determine your required daily calorie intake based on factors like age, gender and activity level. As a general rule of thumb, however, men and women need around 2,500 calories and 2,000 calories per day, respectively, to help maintain weight.
3. Make a Meal Plan
Once you’ve calculated your daily nutrient needs and decided which fasting method works for you, you can begin planning out your meals to get started with keto and intermittent fasting.
Fill your plate with plenty of healthy fats, such as coconut oil, avocados, olive oil, ghee and grass-fed butter as well as moderate amounts of protein foods like grass-fed meat, free-range poultry, fatty fish and eggs. Non-starchy vegetables, fresh herbs, nuts, seeds and healthy beverages like water, bone broth and green tea can all be enjoyed as well.
4. Get Started!
Now that you’re properly prepared, it’s time to get started with intermittent fasting keto. In addition to cutting carbs, increasing fat intake and restricting food consumption to a specific window of time each day, you should also be sure to stay hydrated and plan your workout routine around your fasting schedule. While exercising is okay during days that you fast, it’s important to listen to your body and avoid pushing yourself too hard.
So how long does it take to go into ketosis when fasting? On a standard keto diet, it typically takes around 2–3 days to reach ketosis, although it can take up to seven days in some cases. However, many people find that keto adaptation intermittent fasting can speed up the process and help your body burn through glycogen stores more quickly to help enter ketosis.
Keto Fasting Precautions
Although intermittent fasting and keto can be safe and effective for most, it may not be right for everyone.
For those with low blood sugar, for example, going long periods without eating can drop blood sugar levels and cause adverse side effects like weakness, shakiness and sweating. Therefore, if you have diabetes, you should consult with your doctor to determine if intermittent fasting keto is right for you.
Intermittent fasting keto is also not recommended for children, women who are pregnant or those with a history of eating disorders. Instead, it’s best to focus on a nutrient-rich diet that can help provide the important vitamins and minerals that your body needs.
Additionally, although many people use intermittent fasting keto for bodybuilding, it’s best to listen to your body when it comes to fasting and physical activity. While light exercise is typically fine, it’s recommended to limit exercise when fasting for 72 hours or more.
Finally, note that fasting to induce ketosis can also trigger a set of symptoms often known as the “keto flu.” Fasting ketosis symptoms may include decreased energy levels, increased cravings, digestive issues, muscle aches and dizziness. These symptoms can last between a few days to a few weeks when starting the ketogenic diet, but they typically subside once your body enters ketosis and begins to adapt.