Guest Post: Why Is Ketosis Good for Endurance Athletes?

From time to time I let people guest post on my blog.  This article is by Brian Griffin, an Austin fitness center owner, and it explains the benefits of a keto diet for those of you interested in doing endurance sports like mud runs and triathlons.  All words and photos are his and his contact info is at the end of the article.  Enjoy!

Why Is Ketosis Good for Endurance Athletes?

As more and more elite endurance trainers state that they prefer ketogenic and carb restricted diets, it’s easy to see why they’ve become so popular. Ketogenic diets offer endurance trainers two specific advantages over traditional nutritional dieting: fat loss and sustained energy.

How does this happen? While your body is in ketosis, instead of burning glucose for fuel, your body  burns fats. Once you’ve entered ketosis and are stable in a keto diet, you’ll find that your energy is not dependent on sugar spikes, and instead your body has an efficient way of keeping you energized by burning fat.

What is Ketosis?

Ketosis is the process of your body making ketones. Ketones occur naturally in your body during periods of extended exercise, starvation, and in carb restricted diets. These ketones are converted into energy for your body and your brain.

Burns fat for fuel

During intense exercise, your body prefers glycogen because it can burn through sugars quickly. For endurance exercise, and exercise lasting longer than an hour, your body runs out of glycogen and starts crashing, at which time you can either refuel yourself with more sugar, or your body will switch to using fat. For endurance performance, burning fat through ketosis is preferred, because you never get the sense of peaking, and your energy can remain at a consistent level.

Sustained Energy comparative to sugars

Carb loading, eating sugary gels, and drinking sugar-filled sports drinks are all common during endurance activities, but your body can only hold a finite amount of carbohydrates in your muscles. Loading up on carbs and sugars can cause severe sugar spikes, and without continuous fuel, your body can run empty mid race. Meanwhile, if your body uses fat for energy instead, you can pull from a much, much larger reservoir of energy in the stored fats throughout your system.

How do you get into ketosis?

Ketogenic diets are high fat, moderate protein, and as few carbs and sugars as possible. Any carbs you eat you should come from vegetables preferably. You’ll want to eat plenty of fatty foods as your source of energy, so say yes to butter and cream in your coffee.

In order to maintain a keto diet for race day, it’s recommended you start keto 3 months before race day

What should you eat on a keto diet?

High fat, moderate protein, as few carbs as possible. Try to include coconut or MCT oil in your diet for added fats. Meats, dairy and leafy green vegetables are preferred, and sugars, fruits, and all grains should be avoided. There’s a full list of foods to eat on a keto diet and other low carb diets that can help you find what foods you should have, and what you should avoid.

What should you eat the day before the big event?

Avocadoes are rich in nutrients and healthy fats, and can provide the right nutrition to load up on before your race. Red meat or fish are also good for their high protein and fat content, as are nuts in moderation.

What should you eat on race day?

On race day, a proper keto diet won’t need to load up on carbs every hour or so, so there’ll be less likelihood you’ll need to snack a lot during the race.  Normally a healthy meal with fatty MCT or coconut oil and a protein source is recommended before the event.

When you need a boost during your endurance activity exogenous ketones can give your body the extra push it needs for sustained energy.  Exogenous ketones provide ketones in addition to the ones your body produces naturally. This can lead to extended energy without the crash that would accompany a sugar snack.

The ketogenic diet is not only good for those looking to lose weight, but also for elite endurance athletes. At optimal levels of nutrition, a ketogenic diet can keep you going longer than traditional diets when you need it most.


Brian Griffin is the owner of Blue Tree Health Integrative Medicine, a weight loss and wellness clinic in Austin, TX. A retired Army combat medic, Brian has committed his life to health and fitness. In his free time, he likes hiking with his wife and son and running with his dogs.

You can find him here:

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