Once praised for its rapid weight loss effects, the keto diet has garnered attention from athletes seeking a performance edge. However, carbohydrates have long been considered the best fuel for fitness, raising the question: is keto good for athletes? While there is some evidence suggesting that the keto diet may offer health benefits for certain populations, it remains unclear whether this dietary trend can improve athletic performance.

Let’s explore the research to determine the potential benefits of the keto diet for athletes and the possible drawbacks of following this type of nutrition plan.

What is the Keto Diet?

Although there are some variations, the standard keto diet is very low in carbohydrates, high in fats, and moderate in protein. The diet typically provides about 80% of calories from fat, 15% from protein, and only around 5% from carbohydrates. During the keto diet, you drastically reduce carbohydrate intake and replace it with fats.

Many athletes on the keto diet will include large amounts of fat and moderate amounts of protein, such as:

• Butter
• Oils
• Avocado
• Coconut
• Meat
• Fish
• Cheese
• Eggs
• Nuts

The diet also allows for vegetables that are low in carbohydrates, such as:

• Lettuce
• Spinach
• Kale
• Cucumbers
• Carrots
• Cauliflower
• Zucchini

Most fruits, legumes (beans), grains like oats, bread, pasta, rice, and cereals are eliminated.

It’s important to note that athletes on the keto diet must still ensure they are consuming enough calories for training, whether those calories come from fats or proteins.

How Does the Keto Diet Work for Athletes?

Carbohydrates are the primary source of energy for your muscles and brain. When you consume carbohydrates, your body can use this fuel immediately or store it 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, known as ketones, is used for energy instead of the sugar derived from carbohydrates.

To reach a state of ketosis, you need to consume less than 50 grams of carbohydrates per day. Just to put this in perspective, one medium-sized banana contains about 27 grams of carbohydrates. As you can see, restricting carbohydrate intake to achieve ketosis is extremely restrictive and eliminates several nutrient-dense, whole foods.

To stay in ketosis, it’s also necessary to limit protein intake. Studies have shown that consuming too much protein can affect ketosis since protein can be converted into glucose (sugar).

Potential Benefits of the Keto Diet for Athletes

Given all the buzz surrounding the keto diet, you may wonder if it’s beneficial for athletes. The keto diet has become popular as a weight-loss tool. In fact, research has shown a strong link between the keto diet and weight loss.

As such, the diet may appeal to athletes as a weight-loss tool, particularly endurance athletes who want to improve their body composition. A small 2017 study involving five endurance athletes showed that a 10-week keto diet improved the body composition of the athletes.

However, it’s difficult to make general conclusions based on these results, given that the study involved only five participants and lasted for a very short period (less than 3 months). It’s also worth noting that the participants did not experience improvements in athletic performance during the keto diet.

Another study from 2016 analyzed the difference in metabolic rate between ultra-endurance athletes on a keto diet and those on a high-carbohydrate diet. Researchers found that the athletes on the keto diet burned twice as much fat as those on the high-carb diet. This could provide them with more energy for maintaining longer, lower-intensity workouts.

This research suggests that the ability to use fat for energy could help endurance athletes train for longer periods.

Drawbacks of the Keto Diet for Athletes

While there appear to be some potential benefits of the keto diet for athletes, it’s important to understand the potential drawbacks of eliminating an entire group of foods, such as carbohydrates.

A recent systematic review attempted to examine the effect of the keto diet on athletic performance compared to regular diets without the keto approach. Researchers concluded that in most studies, the keto diet was not beneficial for endurance athletes. In two studies, the keto diet even had a negative impact on physical performance.

The keto diet allows only moderate protein intake because excessive protein consumption can interfere with ketosis. While this eating plan might work for inactive individuals, it may deter athletes who want to increase muscle mass.

Additionally, for athletes engaged in more intense exercises like sprinting, high-intensity interval training (HIIT), or weightlifting, all of which rely on carbohydrates as the primary fuel source, following a keto diet may hinder performance.

In fact, recent research suggests that high-intensity, short-duration exercises may be negatively affected by the keto diet and may delay the recovery process.

During the initial days and weeks of starting the keto diet, people often experience what’s known as the “keto flu.” The keto flu is characterized by various unpleasant symptoms as the body adapts to ketosis. Common symptoms of keto flu include headaches, nausea, fatigue, confusion, and irritability.

Studies have noted that during this transitional period, athletic performance is limited, running speed is slower, and subjective effort at all intensity levels is increased.

Conclusion

Current evidence on whether the keto diet is helpful or detrimental for athletes is mixed. On one hand, the keto diet may improve body composition and the ability to burn fat for fuel, which may help with longer training during endurance events.

On the other hand, the keto diet doesn’t seem to offer any performance benefits, especially during high-intensity, short-duration exercises. Furthermore, the keto diet is often accompanied by keto flu, which may interfere with both training and performance.

As a sports nutritionist, my concerns regarding the keto diet include the increased risk of insufficient food intake and nutrient deficiencies that can occur when so many foods are restricted.