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Ketosis For Athletes: Can Athletes Eat Keto Without Affecting Performance?

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Despite being a huge advocate for ketogenic dieting, I do not believe that a pure ketosis diet is always the best diet for certain types of individuals. Many athletes and high performers worry that the ketogenic diet will negatively affect their energy levels and power output, and their fears are not entirely unfounded. 

The ketogenic diet for athletes is very difficult, especially during the adaptation phase. This is where the body goes through the process of switching from using glucose for fuel to using ketones. This is a big reason why I do not recommend for athletes to switch to a keto diet in the middle of their athletic seasons. Such a transition should be done during the off season or during a lull in competition. 

But I also do not think that we should throw the baby out with the bathwater. As we have seen in some recent studies, in the fat adapted athlete, the ketogenic diet can be an outstanding tool for increasing athletic performance. As we’ve seen with Doctor Jeff Volek’s studies on the ketogenic diet in extreme endurance athletes, athletes who are keto-adapted can have a much higher rate of fat oxidation while training than non adapted athletes. 

Additionally, the increased presence of ketones in the blood stream is associated with maintenance of muscle mass, increased brain health, along with higher athletic performance. 

So the question becomes how can athletes take advantage of the benefits of ketosis without experiencing lulls in performance, whether they are temporary or not?

Enter our friends intermittent fasting and cyclical ketosis for athletes...

These are two similar, but distinct methods of getting the benefits of having increased ketones in your blood stream without entering full blown ketosis. Both have their benefits, and I will let you decide which one is best for you. 

Intermittent Fasting

Intermittent fasting is nothing new. People have fasted for religious purposes for thousands of years, and I do not think that the connection between fasting and reaching a higher religious state or a higher state of consciousness is a coincidence. More ketones in the blood stream means a steadier supply of fuel to the brain along with less inflammation. As such, many individuals who fast report an almost euphoric feeling.

Fasting also has many other health benefits. It will lower our blood sugar, and in turn, lower our secretion of insulin. This results in less fat storage and increased fat mobilization for those seeking to lean out. Additionally, when we secrete insulin and leptin, which happens when we eat, we secrete less growth hormone and testosterone precursors like luteinizing hormone. For men in their 30s or older, this means that we increase the natural presence of anabolic hormones in our bodies. That means more muscle, better sex drive, and increased athletic performance. 

Additionally, some scientists suggest that fasting induces cellular autophagy. In as simple terms as I can put it with my layman mind, this is a process where the body kills off diseased cells in order to create new ones in a self-detoxifying process. 

So how do you incorporate fasting into your diet protocol?

The first thing to remember is that you need to eat at some point. You cannot fast forever. If you try, you’re simply starving yourself. That’s called anorexia and it leads to death. 

But fasting for 8, 12, 24, or 36 hours at a time can raise your level of blood ketones.  I have heard of people effectively doing 3 day fasts and feeling fine, one of which is Jocko Willink. Jocko’s a retired US Navy Seal and Jiu Jitsu Black Belt who can do 67 pull-ups without stopping. You’re probably not Jocko or a Navy Seal, so I’ll fall short of recommending the three day fast if you are new to this. 

As far as the fast goes, I recommend starting with something shorter. Start by not eating for two to three hours before you go to bed, and then avoiding food for two or three hours after you wake up. When you break your fast, avoid carbohydrates until after you’ve done your training for the day. 

If you are going to try to do a longer fast, I recommend that you do put three things into your body during the fast: water, medium chain triglycerides, and minerals. When you fast, you do lose significant amounts of water. Of course this will result in a more chiseled appearance for you meatheads out there, but it could also result in a headache, low energy, and cursing my name for ever recommending such a horrible practice to you. So ensure that you are drinking copious amounts of water, and add a bit of himalayan pink salt to one of your glasses to ensure that you have the minerals in your body to retain it. 

I would also consume medium chain triglycerides. These are medium chain fatty acids that can immediately be converted to ketones to fuel your brain. This can be accomplished by adding a tablespoon or two of coconut or MCT oil to your coffee or tea. The added benefit here is that you can take your fat soluble vitamins, like vitamin D, with these servings for better absorption. 

When you do eat, you should also avoid doing the intermittent fast food run and avoid pigging out on heavily processed junk food. Pigging out will only lead to more inflammation and higher insulin secretion, which will ruin everything you were trying to accomplish with the fast. Trust me, I tried eating French Toast and Pancakes every day for two months to break my fast. That ended up with me becoming near pre diabetic and a VA Nurse yelling at me about my levels of hemoglobin A1C. 

Break your fast with meals based on whole foods, good fats, vegetables, and moderate complex carbohydrates. 

Cyclical Ketosis

As the name suggests, cyclical ketosis follows a cycle where you are in ketosis for most of the week. During this time you follow a strict ketogenic diet of very high fat intake and low protein and carbohydrate intake. After about 5 to 6 days of doing this you begin a heavy carbohydrate re-feed by reducing the fats and eating high amounts of complex carbohydrates and protein. Then you jump back into the keto cycle by returning to the strict keto diet. 

This method’s biggest following is in the hardcore bodybuilding world through the work of the guru Dan Duchaine and Dr. Mauro Dipasquale.  As you would expect coming from the bodybuilding genre, the biggest benefit to a cyclical ketosis diet is that it helps to build lots of muscle while simultaneously allowing you to burn fat. 

The biggest negative here, however, is that cyclical ketosis requires lots of discipline and the ability to deal with a whole lot of pain. Because of the carb refeeds, it is imperative that you stick to an extremely strict keto diet for the rest of the week, and due to these refeeds, you need to adapt back into ketosis each week. That means that those five to six very low carb days are going to be in a pretty severe energy deficit, and unless your workouts consist of really slow pump up exercises, like they would in a bodybuilding routine, you’re going to be feeling less than optimal during training.

Don’t get me wrong, I’ve seen cyclical ketosis work extremely well as far as fat loss and muscle building, but I think there’s a better alternative. Rather than re-feeding once a week on massive amounts of carbs, I’ve turned to re-feeding each night on smaller amounts of carbs after my workouts and Jiu Jitsu practice. This allows me to use the carbohydrates I do eat more effectively by using them to replenish glycogen after I’m depleted from the workout. If you have been adapted to ketosis for a while and are insulin sensitive, you could remain in ketosis with up to 100-150 grams of carbohydrate intake on days when you’ve been very active and have depleted a lot of glycogen.  Jeff Volek and Stephen Phinney also note this in their book, The Art and Science of Low Carbohydrate Performance. 


I do need to give you a note of caution here. Nothing that I’ve just said is set in stone. Every person metabolizes differently. You might take in 60 grams of carbs and get knocked right out of ketosis. But you’ll be more likely to handle the carbs and remain in ketosis if:

  1. You have been fat adapted for a while.

  2. You only eat the carbs after you’ve been glycogen depleted. 

Conclusion: Athletes Should Eat Differently Than Others

If you are an athlete, a military member in a combat MOS, or someone who’s job is extremely physical, you cannot be expected to follow the same diet as a less active person and have success with it. This should not come as a surprise. Regardless of the nutritional paradigm, athletes have always eaten differently than the general population. You have nutritional needs that others do not, and you need to be able to keep up with your level of performance. 

Despite the criticism from certain hardcore keto advocates, one promising way of getting into nutritional ketosis while maintaining performance is through exogenous ketones like Kegenix. This product contains powdered beta-hydroxybutyrate and MCT oil that could help to fuel you while you are trying to adapt. In my experience, they have been very helpful in increasing energy and brain power during the adaptation phase so that didn’t have any lulls in my training. 

If you are having issues adapting or are considering becoming a fat adapted athlete, sign up for our newsletter and we’ll send you our complete keto-adaptation primer for free along with more information on how you can leverage ketosis to improve your performance, fat loss, and muscle building. We’ll also send you a free grocery list and some delicious low carb recipes! 

Additionally, if you are interested in learning how to optimize your diet for health and mental and physical performance through ketosis, check out Warrior Soul Keto Camp. It contains everything you need to know to get into ketosis quickly and leverage its benefits to burn fat and attain superhuman performance including: a full adaptation nutrition program, a full maintenance nutrition program, 12 weeks of workouts, a 30 recipe cookbook (that includes recipes for keto desserts like pumpkin pie and cheesecake), and the opportunity to work with experts who will help you along your way!

Until next time, train hard and eat fat!

Chris, Warrior Soul Life