Once a diet praised for its rapid weight loss results, the keto diet has garnered the attention of athletes looking for the superior performance edge.
However, carbohydrates have long been considered the best fuel for fitness, which begs the question, is keto good for athletes? While there is some evidence to suggest that the keto diet may offer health benefits in certain populations, the jury is still out on whether this dietary trend can play a role in enhancing athletic performance.
Let’s explore the research to determine any potential benefits of keto for athletes and the potential downsides of following this type of diet.
What is the keto diet?
While there are some variations of the diet, a typical ketogenic diet is very low in carbohydrates, high in fat, and moderate in protein. The diet typically provides about 80% of calories from fat, 15% from protein, and only about 5% from carbohydrates. While following the keto diet, you are essentially drastically reducing your carbohydrate intake and replacing it with fat.
Many keto athletes will include a high amount of fat and moderate amounts of protein in their diet such as:
Butter
Oil paintings
Avocado
Coconut
Meat
Fish
Cheese
Eggs
nuts
The diet also allows low-carb vegetables such as:
Lettuce
Spinach
Cabbage
cucumbers
Asparagus
Broccoli
Cauliflower
Pumpkin
Almost all fruits, legumes (beans), grains such as oats, bread, pasta, rice and cereals are eliminated.
It is important to note that keto athletes must still fuel their training with adequate calories whether those calories come from fat or protein.
How does keto work for athletes?
Carbohydrates provide the main source of fuel for your muscles and brain. When you consume carbohydrates, you can use this fuel source immediately, or it can be stored as glycogen in your muscles and liver for later use.
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 instead of sugar from carbohydrates.
To achieve a state of ketosis, you will need to eat less than 50 grams of carbohydrates per day. Just to put it in perspective, there are about 27 grams of carbs in a medium size banana. As you can see, drastically limiting your carbohydrate intake to achieve a state of ketosis is extremely restrictive, eliminating many nutritious, whole foods.
To stay in ketosis, it is also necessary to moderate your protein intake. Studies have shown that eating too much protein can affect ketosis as protein has the potential to be converted to glucose (sugar).
Potential benefits of keto for athletes
With all the buzz around keto, you might 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 relationship between the keto diet and weight loss.
Therefore, the diet may appeal to athletes as a weight loss tool, particularly endurance athletes who may want to improve their body composition. A very small one 2017 study five endurance athletes found that a 10-week keto diet improved the athletes’ body composition.
But it is difficult to make generalizations about these results, with only five study participants, and a very short duration (less than 3 months). It is also important to note that study participants did not show any improvement in athletic performance while following a keto diet.
Other 2016 study analyzed the difference in metabolic rate between ultra-endurance athletes on a keto diet compared to those on a high-carb diet. Researchers found that athletes on a keto diet burned twice as much fat as those on a high-carb diet. This can give them more energy to sustain a longer workout at lower intensities.
This research shows that the ability to use fat for energy can help endurance athletes exercise for longer periods of time.
The cons of keto for athletes
While there appear to be some potential benefits of keto for athletes, it is important to understand the potential downsides of eliminating an entire food group such as carbohydrates.
A recent systematic review sought to examine the effect of the keto diet on athletic performance compared to a normal 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 only allows for moderate protein intake, as eating too much can interfere with ketosis. While this diet plan can work for a sedentary lifestyle, it can deter athletes looking to increase their lean muscle mass.
Additionally, for athletes who engage in more intense exercise such as sprinting, high-intensity interval training, or weightlifting, which rely on carbohydrates as their primary fuel source, the keto diet can hinder performance.
Yes, recently research suggests that high-intensity, short-duration exercise may be adversely affected by a keto diet and may delay the recovery process.
During the first few days and weeks of starting the keto diet, people often experience the “keto flu.” Keto flu is characterized by a variety of unpleasant symptoms as your body goes into ketosis. Common symptoms of ketoflu 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 effort at all intensity levels increases.
The bottom line
Current evidence on whether the keto diet is beneficial or hindering for athletes is mixed. On the one hand, the keto diet can improve body composition, and burning fat for fuel can allow you to exercise longer during endurance events.
On the other hand, the keto diet does not appear to offer any benefit in terms of athletic performance, particularly during high-intensity, short-duration exercise. Additionally, the keto diet often comes with keto flu which can impair both training and performance. As a sports nutritionist, my concerns about the keto diet are the increased risks of malnutrition and nutrient deficiencies that occur when so many foods are restricted.
Many athletes, especially professional keto athletes, will seek guidance from a registered dietitian to ensure their bodies are fueled properly for maximum performance and recovery.
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