Dr. Anthony Gustin is a board-certified sports chiropractor, functional medicine practitioner, entrepreneur, podcast host, and founder of Perfect Keto.
Since going keto means greatly reducing carbs, and since carbs are the body’s primary source of fuel, you might be wondering what your options are when it comes to how to exercise while in ketosis.
The good news is that while there are some things to keep in mind, exercise is totally possible on the ketogenic diet and even has some big benefits health- and energy-wise. These are important to know when wading through any misconceptions or poorly-understood topics around low carb eating and working out such as how to build muscle on keto or how many carbs you can actually eat on keto when you exercise often.
Exercising in Ketosis
First, let’s note that the traditional view of weight loss—simply eating less and exercising longer, often with long bouts of cardio—is outdated and unsustainable. In order to see real results when it comes to losing weight and getting leaner, what you eat really matters. A great place to start is checking out a guide on sourcing meat, dairy, and seafood. Therefore, paying attention to the quality of your ketogenic diet itself, and maintaining a steady state of ketosis, is the most important first step you can take. To see if you are actually in a metabolic state of ketosis, testing your ketone levels is vitally important.
However, exercise also has many benefits for your health. It’s good for the heart, builds muscle to keep you lean and toned, and strengths the bones. Thankfully, exercise can completely fit into your routine while eating for ketosis. You just need to keep in mind a few simple considerations:
Type of Exercise
Nutritional needs vary depending on the type of exercise performed. Workouts styles are typically divided into four types: aerobic, anaerobic, flexibility, and stability.
Aerobic exercise, also known as cardio exercise, is anything that lasts over three minutes. Lower intensity, steady-state cardio is fat burning, making it very friendly for the keto dieter.
Anaerobic exercise is characterized by shorter bursts of energy, such as from weight training or high-intensity interval training. Carbohydrates are the primary fuel for anaerobic exercise, so fat alone can’t provide enough energy for this type of workout.
Flexibility exercises are helpful for stretching out your muscle, supporting joints, and improving muscle range of motion. Increasing your flexibility can help prevent injuries caused by shortening of the muscles over time. Yoga and simple after-workout stretches are good examples of this.
Stability exercises include balance exercises and core training. They help improve your alignment, strength muscles, and control of movement.
When you’re in ketosis, the workout intensity matters as well:
- During low-intensity aerobic exercise, the body uses fat as its primary energy source.
- During high-intensity aerobic exercise, carbohydrates are normally the main energy source.
When you’re in ketosis, you’re using fat as your primary energy source. This can make high-intensity exercise, namely anaerobic exercises, more difficult at the beginning of the diet. But there’s a solution:
How to Use a Targeted Ketogenic Diet for Exercise
If you do exercise that is more intense, such as working out more than three days a week and at high intensity, like sprinting or weightlifting, you’ll need to adjust your keto diet to fit your carb needs for your amount of exercise. Simply sticking to the standard ketogenic diet likely won’t be enough in this case.
A good rule of thumb is to eat 15-30 grams of fast-acting carbs, such as fruit, within 30 minutes before your workout and within 30 minutes after. This will ensure you provide your muscles with the proper amount of glycogen to perform during the training and also recover. It allows the carbs to be used exactly for this purpose and prevent any risk of leaving ketosis.
Types of Ketogenic Diets
The difference between each ketogenic diet type depends on carbohydrate intake.
Standard Ketogenic Diet (SKD): 20-50 grams of net carbs per day
Targeted Ketogenic Diet (TKD): 20-50 grams or less of net carbs taken 30 minutes to 1 hour before exercise, best for athletes with high-intensity activities
Cyclical Ketogenic Diet (CKD): Eating low-carb keto for several days, then eating higher-carb for a couple of days
Other than this change, you can continue with the standard keto diet ratios during the rest of the day, and a normal keto diet should be fine for low or moderate aerobic, flexibility, and stability exercises.
The good news is that as the body adapts to low-carb eating and using fat for fuel (which typically takes around 2-3 weeks), exercise performance value can greatly increase. Since the body isn’t getting carbs for energy, it must turn to the secondary form: fat. This can change how the body utilizes energy when working out, as the preferred source for muscles, glycogen, isn’t as present without carbohydrate intake.
However, the longer someone remains on a low-carb, ketogenic diet, the body goes through what’s known as keto-adaptation—becoming more efficient at burning fat and using ketones for fuel. This adaptation plays a powerful part in more efficiently burning fat during exercise.
Health Benefits of Exercise in Ketosis
It might seem like ketosis is a hindrance to long-term exercise, but it actually has shown to provide significant benefits:
- In one recent study, during a three-hour-long run, 2-3 times more fat burn was seen in ultra-endurance athletes who ate low-carb for an average of 20 months versus those following a high-carb diet.
- In the same study, the low-carb group used and replenished the same amount of muscle glycogen as the high-carb group.
- Being in ketosis might also help prevent fatigue during longer periods of aerobic exercise.
- Plus, ketosis has been shown to help with blood glucose maintenance during exercise in obese individuals.
- As mentioned above, the power of keto-adaptation helps low-carb dieters perform better in all forms of exercise with less carbs over time.
Historical Evidence for Ketosis Benefiting Exercise Performance
Besides what we know today, we also have records showing the power of ketosis for movement and peak physical performance.
- For example, demographic verification of European cultures from the past has shown us people were living as mostly hunters, meaning they had very little dietary intake of carbs and were still functioning without any physical hindrances.
- Before the diets of the Inuit people were altered more, their traditional diet was virtually devoid of carbs with a heavy emphasis on animal foods and no known problems. They also were hunters, meaning prolonged steady movement was required for survival.
Although ketosis might get a bad rep in terms of exercise due to popular carb-heavy philosophies, the truth is the diet has a healthy place within a regular low or moderate exercise routine and can easily be adapted to fit the lifestyles of those who are more active. It just takes a little tweaking to find what works best for you.