The ketogenic or “keto” diet is the hot diet right now. Made popular by celebrities and athletes alike, this very low-carbohydrate, high-fat diet goes against almost every traditional nutrition recommendation for athletes, in that it severely limits carbs. Generally, athletes are encouraged to eat a certain amount of carbs before and even during an event for sustained energy. Carbohydrates, after all, are the number one fuel source for our cells. So, as an athlete, is keto right for you? Can such a low-carb diet support athletic performance?
The ketogenic diet was first used as a treatment for epilepsy in 1911. It fell out of favor mid-century with the discovery of drugs to control seizures. It had a revival in the mid-1990s due to a TV movie about a boy with epilepsy who was successfully treated with the diet. Like almost every fad diet, keto is not “new.”
The ketogenic diet severely restricts carbohydrates to 20-50 grams per day in order to produce a metabolic state called “ketosis.” While in ketosis, the body switches to using ketone bodies as fuel instead of glucose. Ketone bodies are made from fat, which is why the keto diet is a popular weight-loss method. Once you are in ketosis, you can tap into the fat stores in your body for energy instead of relying on your limited carb stores. People report feeling less hungry while on keto, likely due to the hormonal and metabolic shift that occurs and to the increased intake of protein.
There is some interest in using keto for athletes to prevent “burnout,” when the body runs out of glucose during an athletic event. If the body is in ketosis and burning fat at the start, in theory one should never run out of energy. There are more than 80,000 calories of energy stored as fat in the body; you could run a lot of marathons on those calories! But there is some concern that for athletes, a ketogenic diet may be harmful in terms of performance and recovery. Research on athletes eating a keto diet is currently mixed.
A 2016 study of ultra-endurance athletes evaluated the difference in metabolism between those on the ketogenic diet and those following a high-carbohydrate diet. The athletes on keto burned 2.3 times as much fat as those on a high-carb diet, which would allow them to have more energy to sustain a workout over time. This study suggests that for endurance athletes, being able to easily utilize fat for energy may help them exercise longer and support fat loss. There is also some evidence that the ketogenic diet can help prevent oxidative stress in athletes, speeding recovery.
On the flip side there is also evidence that keto may not be right for certain types of athletes. Performance, especially at a high intensity, may be impaired on a ketogenic diet due to low blood sugar and lack of muscle glycogen. This is particularly true for athletes who participate in “sprint-like” activities, such as heavy weightlifting, who need access to quick energy for their event.
At this time, the evidence as to whether the ketogenic diet is right for athletes is mixed. Being able to switch into ketosis and use fat for energy may help you exercise longer, but the lack of carbohydrates could impact your intensity. The appropriateness of the ketogenic diet may also depend on what type of activity you perform and if you need a quick burst of energy that only carbohydrates can provide. As of now, it’s best to proceed with caution and evaluate the diet based on your individual goals.
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