Intermittent Fasting and the Keto Diet

Last Update: May 17, 2023

When it comes to trending weight loss plans, two diets in particular are gaining popularity for their ability to deliver results quickly. The keto diet promotes reducing your daily carb intake and upping your intake of fat and protein. Intermittent fasting recommends daily periods of going completely without food. But both plans have the same goal in mind: getting your body to burn fat fast. So what happens when you combine the keto diet with intermittent fasting? Some say this is the secret to getting the results you’re after as soon as possible. Why? Because both plans work with your body’s chemistry to boost metabolism and could potentially work in tandem with one another to make that happen efficiently. So is a keto diet that includes intermittent fasting the best of both worlds? Here’s a closer look at this controversial weight loss approach.

What Is Intermittent Fasting?

Generally used as an approach to weight loss, intermittent fasting (IF) involves cycling between periods of eating and fasting. While the food we eat is typically broken down into sugars that become energy used by our cells, whatever doesn’t get used is instead stored as fat. However, during periods of fasting, insulin levels will drop and prompt our fat cells to release this stored sugar to instead be used as energy. In other words, intermittent fasting can promote weight loss by lowering insulin levels and causing our body to burn fat. While most of us are technically fasting while we sleep, intermittent fasting could involve extending this period to include skipping breakfast or eating the final meal of the day earlier in order to squeeze more fasting hours into a 24-hour period.

Is Intermittent Fasting Healthy?

Despite its recent popularity as a wellness phenomenon, intermittent fasting can be somewhat controversial and may not be for everyone. It’s important to discuss your nutrition plan with your doctor first.

If you do choose to try IF, there are a variety of health benefits you may experience, including the following:

  • Weight loss: Perhaps the biggest draw to IF is its positive effect on weight loss and its ability to decrease fat mass. In fact, one study found that short-term fasting can increase your metabolic rate by 3.6 to 14 percent.
  • Lower blood sugar: Studies demonstrate that IF can benefit insulin resistance and lower blood sugar from 3 to 6 percent
    Reduce oxidative stress: Several studies show that IF can enhance the body’s resistance to oxidative stress (an imbalance of free radicals and antioxidants in the body)
  • Healthy heart support: IF has been shown to help support both healthy blood pressure and levels of good cholesterol

What is Keto Intermittent Fasting?

Like IF, a keto diet is designed to put your body into a fat-burning metabolic state (known as ketosis) by boosting the presence of ketones, a byproduct that’s produced by the body when breaking down fat for energy. A keto diet involves dramatically reducing your daily carb intake in order to reach ketosis (a standard keto diet involves an intake of 75% fat, 20% protein, and 5% carbohydrates per day). However, many have opted to combine a keto diet with IF in order to maximize potential weight loss benefits by jumpstarting ketosis (since IF works to drop insulin levels and boost ketones while keeping your metabolism high).

What is an Intermittent Fasting 16/8 Keto Meal Plan?

A 16/8 IF fast on keto refers to a fasting technique where you fast for 16 hours of the day (during most of which you will be sleeping) and eat during a specific 8-hour period. The plan involves skipping breakfast (though water, coffee, and tea are allowed) and eating keto-friendly foods between 1 p.m. to 8 p.m. In an 8-week study in 34 resistance-trained men, those who practiced the 16/8 method of intermittent fasting lost nearly 14% more body fat than those following a normal eating pattern.

What is an Intermittent Fasting 20/4 Keto Meal Plan?

One of the strictest IF plans is the 20/4 plan or “Warrior Diet.” The 20/4 formula involves 20 hours of fasting and 4 consecutive hours of eating keto-approved foods (aka your “eating window”). The hours you choose as your eating window are up to you. Many prefer to start the day with coffee only and save their 4 hours for late in the day (from 2 p.m. to 6 p.m. for example). While 20 hours is a long time to go between eating, many keto dieters feel that the low-carb, high-fat diet curbs hunger during the time they are fasting.

Best Keto Food to Break an Intermittent Fast

Once your IF period is over, it’s important to fuel up on foods that adhere to keto’s carb restrictions and the diet’s emphasis on healthy fats so you can maintain a state of ketosis. Opt for omega-rich foods and oils, protein, and non-starchy vegetables when breaking your fast.

An example IF keto menu might be:

  • Breakfast (skip) except for water, tea, or keto coffee
  • Lunch (1 p.m.): tuna salad, avocado, greens
  • Snack (4 p.m.): sous vide egg bites
  • Dinner (7 p.m.): grilled salmon with spinach sauteed in coconut oil

(begin fast after dinner)

For more keto meal planning tips and recipes, check out our ketosis guide or our advice on everything from meal prep to delivery options.

For more, check out our ultimate guide to the keto diet!

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Jillian Gordon

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