Once a diet praised for its rapid weight loss effects, the keto diet has garnered the attention of athletes looking for the upper edge in performance.
However, carbohydrates have long been considered the best fuel for fitness which begs the question, is keto good for athletes? While there’s some evidence to suggest that the keto diet may provide health benefits for specific populations, the jury is still out on whether this diet trend can play a role in enhancing athletic performance.
Let’s explore the research to determine any possible benefits of keto for athletes and the potential drawbacks with following this type of diet.
What is the keto diet?
While there are some variations of the diet, a standard ketogenic diet is very low carbohydrate, high fat, and moderate in protein. The diet typically provides approximately 80% of calories from fat, 15% from protein and only about 5% from carbohydrates. While following the keto diet you’re essentially drastically reducing your carbohydrate intake and replacing it with fat.
Many keto athletes will include a large amount of fat and moderate amounts of proteins in their diet like:
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Butter
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Oils
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Avocado
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Coconut
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Meat
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Fish
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Cheese
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Eggs
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Nuts
The diet also allows for low-carbohydrate vegetables such as:
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Lettuce
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Spinach
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Kale
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Cucumbers
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Asparagus
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Broccoli
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Cauliflower
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Zucchini
Almost all fruits, legumes (beans), grains like oats, bread, pasta, rice, and cereal are eliminated.
It is important to note that keto athletes must still fuel their training with adequate calories whether those calories are coming from fat or protein.
How does keto for athletes work?
Carbohydrates provide the primary source of fuel for your muscles and brain. When you consume carbs, you can use this fuel source immediately, or it can be stored as glycogen in your muscles and liver for use later on.
The keto diet works by forcing your body into a state of ketosis. Ketosis occurs when stored fat, also known as ketones, is used for energy rather than the sugar that comes from carbohydrates.
To achieve a state of ketosis, you’ll need to eat fewer than 50 grams of carbohydrates per day. Just to put that into perspective, there are roughly 27 grams of carbohydrates in one medium sized banana. As you can see, restricting your carbohydrate intake drastically in order to achieve a state of ketosis is extremely restrictive, eliminating several nutritious, whole foods.
In order to stay in a state of ketosis, it’s also necessary to moderate your protein intake. Studies have shown that eating too much protein may affect ketosis as protein has the potential to be converted into glucose (sugar).
Potential benefits of keto for athletes
With all the buzz surrounding keto, you may be wondering is keto good for athletes? The keto diet gained popularity as a weight loss tool. In fact, research has shown that there is a strong link between the keto diet and weight loss.
As such, the diet may appeal to athletes as a weight loss tool, particularly for endurance athletes that may want to improve their body composition. One very small 2017 study of five endurance athletes found that a 10-week keto diet improved the athletes’ body composition.
But it is difficult to make any generalizations about these results, with only five participants in the study, and a very short duration (less than 3 months). It is also important to note that study participants experienced no improvement in athletic performance while following a keto diet.
Another 2016 study analyzed the difference in metabolism speed between ultra-endurance athletes following a keto diet versus those following a high carbohydrate. Researchers found that athletes following a keto diet burned twice as much fat as those following a high carbohydrate diet. This might give them more energy to sustain a longer workout at lower intensities.
This research suggests that having the ability to use fat for energy may help endurance athletes exercise for longer periods of time.
The downsides of keto for athletes
While there appears to be some potential benefits of keto for athletes, it’s important to understand the potential drawbacks of eliminating an entire food group like carbohydrates.
One recent systematic review sought to examine the effect of the keto diet on athletic performance compared with a regular, non-keto diet. Researchers found that in the majority of studies, the keto diet was not beneficial for endurance athletes. In two studies the keto diet actually had negative effects on physical performance.
The keto diet allows just a moderate intake of protein, since eating too much can interfere with ketosis. While this eating plan may work for a sedentary lifestyle, it may deter athletes looking to increase their lean muscle mass.
Additionally, for athletes that participate in more intense exercise like sprinting, high intensity interval training, or heavy weightlifting, which all rely on carbohydrates as the primary fuel source, following the keto diet may hinder performance.
In fact, recent research suggests that high-intensity, short-duration exercise can be negatively impacted by a keto diet and can delay the recovery process.
During the first days and weeks of beginning the keto diet people often experience the “keto flu”. The keto flu is characterized by a variety of unpleasant symptoms as your body transitions into ketosis. Common keto flu symptoms include headache, nausea, fatigue, brain fog, and irritability.
Studies have noted that during this transition period, training performance is limited, running pace is slower, and perceived exertion at all levels of intensity is increased.
The Bottom Line
The current evidence as to whether the keto diet is beneficial or impeding for athletes is mixed. On one hand, the keto diet may improve body composition and burning fat for fuel may enable you to exercise for longer during endurance events.
On the other hand, the keto diet doesn’t appear to offer any benefits with respect to athletic performance, particularly during high-intensity, short-duration exercise. Additionally, following the keto diet is often accompanied by the keto flu which can impair both training and performance. As a sports dietitian, my concerns with the keto diet are the increased risks of underfueling and nutrient deficiencies that come when so many foods are restricted.
Many athletes, especially professional athletes on keto, will seek guidance from a registered dietitian to ensure their bodies are fueled properly for peak performance and recovery.
For individualized support and guidance, get on our waitlist to apply for nutrition coaching today.
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