Along with weight loss and epilepsy treatment, one of the most common reasons people turn to the ketogenic diet is for endurance performance. This is because of the unique metabolic switch that occurs when your body is in ketosis.

For decades it was assumed that carbohydrates should be the macronutrient of choice for fueling the body for exercise. However, we now know that the body can not only survive under conditions of low-carbohydrate intake but also perform very impressive physical feats. In fact, as this article will demonstrate, it appears that being fueled by fat and ketones is actually superior for endurance exercise.

Why is this? The answer lies within the dual-fuel power of the ketogenic diet. We’ll go into detail on dual fuel below, but let’s first review the difference between carb-adapted and keto-adapted athletes.

Carb-Adapted Athletes vs. Keto-Adapted Athletes

An athlete who is carb-adapted relies on glucose to provide his or her body with energy during exercise. This glucose comes from carbohydrates consumed prior to exercise and the breakdown of glycogen, our bodies stored form of carbohydrates. 

Glucose can be great fuel for exercise, but the body doesn’t have very much available at any given time. For most people, the carbohydrate fuel tank is around 2,000 calories in the form of glycogen, plus however many calories are consumed from carbohydrates prior to exercise.

While this may be plenty of energy to fuel some types of exercise, it can fall short when attempting to fuel endurance exercise, especially long-duration endurance exercise. This is because the carb-adapted body has difficulty tapping into stored fat, a massive fuel supply, when it runs out of stored carbohydrates. As a result, many athletes experience what is known as a “bonk” or sudden fatigue and a failure to continue exercise. 

This is not the case if you’re a fat- or keto-adapted athlete. A keto-adapted athlete uses fat as the primary energy source for nearly all bodily functions, including physical performance. The great thing about being fat-adapted is that the fat fuel supply is nearly endless; even the leanest athletes store more than 20,000 calories in the form of body fat.

This means that if you are following a ketogenic diet, you have the ability to effortlessly tap into a much bigger fuel supply than you do if you’re carb-adapted. In fact, research has found that ketogenic athletes burn 2.3 times more fat during exercise compared to carb-adapted athletes.

The benefits of being a keto-adapted athlete do not stop here. Besides fat, ketogenic dieters are also able to tap into additional fuel sources–ketones–with relative ease. This is known as the dual-fueled power of the ketogenic diet. 

What is Dual Fuel? 

Dual fuel means being able to utilize more than one energy source. If you are familiar with the ketogenic diet and ketosis, you know that being keto-adapted also means producing and using an additional fuel source known as ketones (which are produced by your body when you eat a higher fat, low-carb diet).

Ketones are important during exercise because they provide energy to the brain to help continue carrying out physical performance. This is especially important since the “bonk” we mentioned earlier can be driven by a lack of fuel available to the brain during exercise. 

Besides being able to use both fat and ketones to fuel exercise, a keto-adapted athlete can also tap into any stored glycogen in the body. This is relevant because, as proven by keto expert Dr. Jeff Volek, even people avoiding carbs maintain ample stores of glycogen that can be called upon by keto athletes if needed during exercise. This is where the true power of the dual-fueled benefit of ketosis comes into play.

While a carb-adapted athlete has a difficult time switching between fuel sources, the opposite is true for the keto-adapted athlete; a keto-adapted athlete can actually rely on fat, ketones, and glycogen to fuel performance. 

Believe it or not, there are even more benefits. Research shows that a keto-adapted body will start burning fat at lower exercise intensities. This allows the body to intuitively preserve glycogen for when a quick burst of energy is needed, like towards the end of an endurance race or when you need that extra push to make it up the hill.

This means that a keto-adapted individual is able to maximize its resources by utilizing various energy sources at the most opportune times during exercise.

The Final Word

Being carb-adapted means missing out on another massive energy source stored within the body: fat. This is the equivalent of being a gas tanker truck and not having enough gas in the tank to complete the journey without stopping to refuel, even though you’re carrying a massive fuel source. If you’re a carb-adapted athlete; once carb energy is depleted, you can’t easily tap into your fat energy, so you need to quickly refuel on sugary gels, sports drinks, and high-carb energy bars to complete endurance performance. If you’re keto-adapted, you will no longer experience the low blood-sugar shakes or need to refuel with surgary options during exercise. Instead, your body has all of the energy it needs thanks to the benefits of a ketogenic diet! 

Watch this video to learn more. 




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