Running A Marathon On A Keto Diet


The Ketogenic Diet is one of the latest diets to become popular. If you’re conscious of what you eat and how it affects your sporting performance, chances are you’ve come across it before.

You may be wondering if running a marathon on a Keto diet is possible or beneficial. We’ll explore what the Ketogenic Diet is all about and its implications for running.

Keep reading to find out whether or not it would be a good option for you!

What is the Ketogenic Diet?

The Ketogenic Diet is an eating plan that involves consuming high amounts of fat, very few carbohydrates, and moderate amounts of protein.

Those who follow a Keto Diet will consume almost 80% of their daily calories in fat!

Keto is very similar to Banting, the Atkins Diet, and other low-carb diets. The difference is that the Keto Diet requires you to be “in ketosis”, whereas other diets don’t.

What is Ketosis?

Ketosis is a state within the body in which the level of ketones in the blood is high. This leads to the next important question…

What Are Ketones?

Ketones are molecules that are created when fatty acids break down in the body. The process of fat breaking down and ketones being released is a normal process in the body.

When your body is producing ketones, it means that you’re in ketosis. In short, this means that your body is burning fat for fuel, rather than using carbs for energy.

This is the idea behind the Ketogenic Diet. By feeding your body more fat and less carbs, the idea is that your body will get used to utilizing fat instead of carbs and you’ll burn fat more easily and naturally.

To remain in a state where your body is producing ketones (ie. to be in ketosis) you’ll need to be consuming less than 50 grams of carbohydrates every day.

For runners, especially those who rely on carbo-loading for enhanced performance, it means that most of their favorite energy-boosting foods are prohibited!

So, Can You Run a Marathon on Keto?

If you’ve been on the Keto Diet for a while and it’s working well for you, then there’s no reason you can’t run a marathon on a Keto Diet!

We don’t recommend trying to switch to Keto before running a marathon if you aren’t used to it. You’ll need to make the transition to eating more fat and less carbs, and it can take some time for your body to adjust.

The biggest mistake people make when they’re new to the Keto Diet is to simply increase the amount of protein they’re eating.

While protein is an essential nutrient, increasing protein doesn’t increase fat. You’ll need to make a concerted effort to eat more fats and reduce the number of carbs you’re eating.

If you do the Keto Diet properly and you’ve been doing it for a while and found that your body does well on it, then you should be able to run a marathon easily.

Considerations for Runners on the Keto Diet

As mentioned above, the most important thing is not to try and switch to a Keto Diet before you’re running a race. Transitioning to a Keto Diet should be done in the off-season, or at least when you’re not training for a particular race.

Once you’ve figured out that it works well for you, you can begin to train for races while on a Keto Diet.

Apart from making sure you’re eating more fats, one of the most crucial things in the Keto Diet is eating the right fats. Not all fats are equal, and choosing to consume the wrong ones can put a real damper on your performance.

Loading your body up with high-fat junk foods won’t work. Your body doesn’t metabolize unhealthy fats the same way, and you’ll only end up feeling worse. Try eating healthy, natural fats and not processed foods.

Training for a Marathon on Keto

Marathon training in itself takes months. But it also takes months for your body to get used to a Keto diet, which is why we suggest getting used to the diet before beginning marathon training.

If you’re going to train for a marathon while on a Keto diet, you’ll need to be extremely disciplined and patient to reap the benefits.

What Should I Eat While Training for a Marathon Keto Diet?

The Keto Diet requires you to eat foods that are low in carbohydrate content or high in fat content.

When transitioning to high-fat foods, your stomach may take some time to get used to it. You may need to experiment a little to find foods that don’t cause tummy troubles. Your stomach should eventually get used to them, but it’s advisable not to eat those foods for a few days before a run.

Once you have a good idea of what foods agree with you, you can put together a Keto eating plan for your marathon training.

A great Keto-friendly pre-workout option is a smoothie. Berries are great Keto fruits, and an avocado added to your smoothie will bring all the healthy fats. Sprinkle in some flaxseed or sunflower seeds for an extra fat boost and top it off with some almond milk.

Nut butter sachets are excellent Keto alternatives to carbohydrate-rich energy chews or gels. You can also stock up on some small packets of sunflower seeds or nuts for snacking on-the-go.

Food to Avoid on Keto

Like all diets, if you choose to follow the Keto Diet, there will be restrictions on what you can and can’t eat.

Some forbidden foods may not seem to make sense, as they’re still healthy foods. But remember, on Keto you’ll be going for the lowest carb and highest (quality) fat foods you can find!

Any sugary foods or drinks should be avoided. This includes soda, store-bought fruit juices, candy, cakes, and so on. Be careful of foods that label themselves “sugar-free” too! They often contain unhealthy sugar substitutes.

Processed foods are also a no-no, as are most condiments. Stay away from low-fat items, as well as unhealthy fats like processed vegetable oils. Alcohol should also be avoided as it’s almost pure carbs.

Now for the healthy foods that should be avoided on a Keto diet. Try not to eat grains or starch, like rice or pasta. You may consume berries, but most other fruits are forbidden.

As for vegetables, stay away from beans and legumes (peas, lentils, chickpeas, etc), and root vegetables like potatoes and sweet potatoes, parsnips, carrots, and so on.

Food to Eat on Keto

Don’t worry if the above list sounds restrictive. There are still plenty of amazing, delicious foods you can eat!

Meat is highly recommended, in just about all forms. Fatty fish like tuna, salmon, and mackerel are an excellent source of healthy fats. Eggs are also a great source of healthy fats. Butter and cream are perfectly acceptable.

Cheeses are great as long as they’re not processed. Cream cheese is a great choice, as is cheddar, goats’ milk cheese, blue cheese, and mozzarella.

Avocados are a wonderful source of healthy fats. You can add one to a smoothie, make guacamole, or eat it just like that!

Healthy Keto veggies include greens, onions, peppers, cauliflower, and squash. For cooking, use a healthy oil like virgin olive oil, coconut oil, or avocado oil. For seasoning, salt, pepper, and various herbs and spices are all perfectly healthy.

Snacking also needs to be high-fat. Nuts and seeds are a super choice, as is nut butter.

Does the Keto Diet Work and Should You Try It?

The Keto Diet definitely seems to work for some people. But on the other hand, it certainly won’t work for everyone. But that’s true for any diet!

If it’s done right and the body responds well, then runners can definitely benefit by training the body to utilize fat stores over long distances.

But do you need to be in ketosis to reap the benefits?

Not necessarily. Some people may find that a diet such as Banting works better for them than Keto. The principle is similar, but it’s not quite as restrictive and you don’t need to “be in ketosis” to find value in the diet.

Runners who do shorter distances may not get much benefit from the Keto Diet. They’re likely to find more value in a balanced diet that gives them quick-access energy from carbs.

Likewise, those who incorporate HIIT into their routines would be better off including carbohydrates in their diet. The body will always grab the carbs first, so when you need them quickly a diet including carbohydrates is the best way to go.

So When is Keto a Good Idea?

If you’re running at lower intensities for longer periods of time, you may benefit from being on a Keto diet.

Your body will be used to burning fat rather than carbs, which could better enable it to use its own fat stores later on in a long race.

The Bottom Line

The Keto Diet may work for some, but it certainly won’t be for everyone. If you’re looking at using it strategically to improve your performance in long, lower-intensity races, then it’s worth a try. But be aware that it will take months to adapt to the diet, and months to train for a marathon.

If you prefer shorter, faster-paced runs, then you’ll most likely do better with some carbs in your system.

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Shanna is a writer who runs... And cycles, jumps rope, and lifts weights. She lives in beautiful South Africa and enjoys sharing her knowledge and experience with other avid athletes.