Training for a Marathon on a Ketogenic Diet

Assumably if you are reading this blog you are interested in distance training while following a ketogenic diet. However, just in case you stumbled upon this and are not presently keto, let’s back track a little and discuss marathon keto.

What Is Keto?

A keto diet is where you eat very low carb and high fat. People eat keto for a variety of health reasons but it has gained in popularity most recently for people working to lose weight. Benefits of keto besides weight loss include less stomach bloat, lowering the glycemic index (good for diabetics), and is said to help improve overall health with benefits touted in regards to lowering risk factors for heart disease, certain cancers, and epilepsy.

When people eat keto they avoid sugar, grains, starches, root vegetables, tubers, and most fruits. If you’re a seasoned distance runner you may have warning bells ringing in your head. After all, aren’t these things most distance runners eat for fuel?

Although most distance runners do fuel themselves on carbohydrates, once you have been on keto for a bit you will find yourself fat adapted. What that means is your body switches over to fueling on fat instead of carbs which are a commonly used source of energy.

Working Out On Keto

If you are new to the keto diet you have probably noticed a drop in your athletic performance. This is because your body is acclimated to fueling with carbs and sugars. The question is: can your body adapt and perform fueling with protein, fats and low carb veggies?

Working Out On Keto

The simple answer is yes, your body will adapt. The complex part of this answer is multifaceted. How long will that adaptation take? Will you be capable of the same times you ran pre-keto?

Keto Diet and Running: Can You Run While On Keto?

Of course, you can run while on keto! However, if you have been running for quite some time and then decide to try a keto diet you will likely see a decrease in performance. People new to the keto diet often report lower energy level and struggling with cardiovascular activity for some time.

The length of time that people struggle with endurance sports when newly on keto truly does depend on the athlete, but according to nutritionists who study athletes, it can take months. Once you are fat-adapted, however, you certainly can go the distance. At least, many people can.

It does bear mention that some athletes never seem to fully adapt to fueling for endurance training while eating keto. These athletes may switch from ketogenic diet for runners to carb cycling or may make the switch from keto to low-carb eating during the higher mileage weeks of training.

Elite Ultrarunner Zach Bitter

Ultra Marathoner Zach Bitter is the 100-mile American record holder. Amazing to watch as he hammers out mile after mile at a 7:00 minute mile pace, it is even more astonishing if you realize that less than 5% of his diet comes from carbs. So before you decide that you can’t train for a marathon while following a keto diet, read up on Zach.

Zach Bitter on Marathon Keto, Zach Bitter

When he was younger he ate carbs just like everyone else and he just didn’t feel right. As he grew as a distance runner he threw convention to the wind and began eating like he felt would work for his body. Unconventional for sure, he eats eggs and bacon most mornings before he hammers out his workout.

Bitter will tell you he noticed a definite drop in energy the first month or so eating keto, but eventually it all stabilized and it was business as usual.

Can You Run a Marathon on Keto?

If you are willing to make fat the primary macronutrient in your diet, you certainly can. Some people make the mistake of thinking they are just increasing protein, but that would be a mistake. If you don’t have enough fat in the diet you won’t be able to fuel yourself for the long haul.

So when asking if you can run a marathon on a keto diet, the answer is yes. There is a “however” to consider. Here are the questions to ask yourself:

How long have you been in ketosis? People new to keto have a difficult time finding the energy for distance running at their pre-keto pace.

Are you eating correctly? You can’t be eating low fat, stay in ketosis, and have the energy to run. You will need a high amount of healthy fats. Notice we said healthy. Sure, eat the bacon. But you also get healthy fats from avocado, nuts, butter, nut butters, chia seeds, hemp hearts, olives, etc.

Do you know how to add low-glycemic index carbs during peak training? This is something you can easily research.

Carb Cycling

Many athletes who eat keto choose carb cycling. To stay in ketosis you generally need to stay under 50 net carbs per day. Not all carbs are created equally, though, and eating the wrong carbs can kick you out of ketosis.

carb cyclcing example

In carb cycling, you do consume a higher number of carbs strategically placed within the workout week. Now we are not talking about candy or cake here, what we mean is high quality, real food carbs such as sweet potatoes or quinoa.

If you place higher carb days around long runs and challenging workouts, you just might get the boost your body needs. That is why some runners prefer keto carb-loading for the marathon.

What Should I Eat During Marathon Keto?

Marathon keto eating looks very different from carb keto eating. The keto athlete would focus on fueling with real foods in their most natural state and probably use carb cycling. First, make a conscious effort to notice which foods do not give you gastro distress. As you probably know many people get an upset stomach when they run after eating a certain food. Avoid these foods the night or morning before a tough or long workout.

If you have always been a fasted runner you may find the switch to keto cycling easier than some people. This is because instead of loading up with carbs before running, you will be acclimated to running without fuel in your body. People who have been regular fasted runners seem to transition easier.

Once you figure out what kinds of foods agree with your gastro system, you are ready to determine which foods you can eat when mixing keto and marathon training. Many people who distance train on keto choose to drink smoothies before a run. You can mix keto-friendly berries like strawberries, raspberries and blackberries, toss in some avocado, add flax and mix it with unsweetened almond milk. This high-fat tasty smoothie is an excellent fuel.

strawberries, raspberries and blackberries

If you find you need to take in fuel while running, there are options for that too. Many runners fuel with small packs of Gu or similar. You can purchase nut butters made and sold in similar packages. Just be sure to bring plenty of water along for washing that down! Another option is small pouches of seeds like sunflower seeds.

If you choose to do carb cycling, you could even fuel yourself before your run with some real food carbs such as a sweet potato or banana. In fact, a half a banana in the aforementioned smoothie might give you just a touch more energy to go the distance.

Athletes such as Zach Bitter show us that, even though most runners fuel their bodies with a carb-heavy diet, it can be done on keto. You just have to experiment with what works for your body! Does that mean it will work for everyone? Absolutely not. But only you can determine if it works for you.

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