In addition to a healthy lifestyle and a nutrient-dense diet, exercise is essential for losing weight and building muscle. Exercise can help define your muscles, boost your mood, and reduce your risk of developing certain diseases. Endurance workouts like HIIT and CrossFit are two of the most popular options for getting fit. But, diet can have a tremendous impact on athletic performance, so you may be wondering if it’s possible to perform high intensity training. How should you exercise on keto?
What Are Endurance Workouts?
Endurance workouts are a type of exercise. The American Heart Association encourages individuals to pursue the four types of exercise:
- Endurance exercise
- Balance training
- Flexibility exercises
- Strength training
Endurance exercise – often called aerobic exercises – increase your heart rate and your breathing rate. As a result, these exercises tend to improve your cardiovascular health, pulmonary health, and circulatory systems. Aerobic exercise also boosts your metabolism, assists in weight loss, improves mood and mental well-being, and reduces blood pressure.
Endurance workouts include:
- High-intensity interval training (HIIT): HIIT exercises include jumping jacks, planks, lunges, burpees, mountain climbers, push-ups and more
- Tabata: This is a type of HIIT in which each exercise is performed for 20 seconds, followed by a 10-second rest for four minutes total. After the initial four minutes, you move on to a second (and third and fourth) exercise with the same 20:10 pattern.
- CrossFit: CrossFit is another type of HIIT that combines strength and conditioning exercises. CrossFit improves your body composition by reducing body fat and increasing lean muscle mass. It also increases endurance. 
- Other exercises like jogging (especially in intervals), bicycling, and swimming
Endurance workouts like HIIT and Tabata are popular because you contain to burn fat even after you’re done working out.  Because the workouts are so intense, they also tend to be shorter workouts. This means that a 30-minute pre-work HIIT workout can burn more calories and more fat than a slower-paced 45-minute bicycle ride. These types of workouts are also appealing because they are fun and versatile. No more slogging away on a treadmill for hours and hours. You can switch up a HIIT workout every time – planks, push-ups, burpees, jumping jacks – so you’ll never feel bored with your routine.
How Your Body Works While You Exercise
There’s no denying that endurance workouts are popular, but are they the best type of workout when you’re on the keto diet? Before we answer that, let’s first go over a little exercise physiology.
When you’re performing endurance exercises, here’s what is going on inside your body:
- When you exercise, your muscles contract, and they use muscles adenosine triphosphate (ATP) as their fuel source to contract.
- ATP quickly runs so your body creates energy via aerobic glycolysis.
- During aerobic glycolysis, your body uses oxygen to convert glycogen and fat into energy. This process can last for our hours.
When you’re on the keto diet, you’re consuming fewer carbs, which means you’ll have less glycogen stores. This is important to know the physiology of exercise because the process of aerobic glycolysis can still convert glycogen and fat into energy– which means your muscles can keep contracting even when you’re on keto.
Working Out Before You’re Fat Adapted
If you work out while you’re on keto, it’s important to know how your workout may be affected until you’re keto-adapted. Studies show that your endurance may decrease temporarily … just until your metabolic state has fully shifted. That’s because your glycogen stores are being depleted before you’re fully capable of oxidizing fat.  The same study found that once a person has been fat adapted – typically a few weeks into ketosis – the fat oxidation is enhanced, and the athletic performance is “maximal.” Other athletes have found that during endurance events, the first sprint times decrease, but overall endurance increases.
Another tip: endurance will likely suffer when you have the keto flu. If you’re in the midst of keto flu, stick with lighter activities like walking or gentle yoga.
Working Out After You’re Fat Adapted
Once you’re fat adapted, the sky is the limit. Even ultra-athletes are performing well on the keto diet. In fact, another study found that ultra-athletes on high-fat, low-carb diets demonstrated a higher potential for performance enhancement and endurance than when compared to ultra-athletes who did not restrict carbs. 
Exercising on Keto
Here are the key takeaways: keto and endurance sports like CrossFit can complement each other well since they both aim to boost the metabolism and blast fat.
Do you have a favorite endurance sport? Share your experience with us!
- Gregory, R. M., Hamdan, H., Torisky, D. M., & Akers, J. D. (2017). A low-carbohydrate ketogenic diet combined with 6-weeks of crossfit training improves body composition and performance. Int. J. Sports Exer. Med, 3, 1-10.
- Wingfield, Hailee L, et al. “The Acute Effect of Exercise Modality and Nutrition Manipulations on Post-Exercise Resting Energy Expenditure and Respiratory Exchange Ratio in Women: a Randomized Trial.” Sports Medicine – Open, U.S. National Library of Medicine, Dec. 2015.
- Cipryan, Lukas, et al. “Effects of a 4-Week Very Low-Carbohydrate Diet on High-Intensity Interval Training Responses.” Journal of Sports Science & Medicine, Uludag University, 14 May 2018.
- Ma, Sihui, and Katsuhiko Suzuki. “Keto-Adaptation and Endurance Exercise Capacity, Fatigue Recovery, and Exercise-Induced Muscle and Organ Damage Prevention: A Narrative Review.” Sports (Basel, Switzerland), MDPI, 13 Feb. 2019.
Kathryn Trudeau is a content writer and educational professional whose work centers on health and wellness and organic living. She has a passion for nutrition and fitness. She loves matcha, running, and crocheting.