The ketogenic diet is definitely the current popular fad diet, made famous by many celebrities who tout its benefits. Several athletes have also jumped on board the ketogenic diet train with the intention of improving their athletic performance, but is it a good diet to support athletic performance?
In case you don’t know, the ketogenic diet is based on achieving a metabolic state called ketosis, by lowering carbohydrate intake to less than 50 grams per day. This causes the body to use ketones (produced from burning fat), for energy instead of glucose. There is a larger store of fat in the body than carbohydrates, meaning that energy from burning fat rather than glucose will last much longer and, in turn, allow for prolonged activity. Athletes are looking to the ketogenic diet to prevent “burnout”, or a drop in energy supply often experienced when blood glucose is used up.
With this potential benefit, researchers are also interested in how a ketogenic diet impacts athletic performance. Strong opinions exist on both sides, so let’s take a closer look at some of the pros and cons that have been found.
On one hand, some research has found that ketogenic diets are beneficial for endurance athletes. A 2016 study found that ultra-endurance athletes on a long-term (average of 20 months) ketogenic diet burned up to 2.3 times more fat than the group on a high carbohydrate diet during a three hour run, in theory allowing them to have more energy for a longer period of time. Other studies have found that fats appear to provide more energy than carbohydrates during both low and high intensity exercise.
Low-carb, high fat diets during low to moderately intense aerobic exercise increase fat metabolism, support weight and fat loss, and help reduce exercise-induced muscle damage. High performance endurance athletes on a ketogenic diet burn over twice as much fat as high carbohydrate athletes during exercise. As a result, some athletes report being able to exercise longer, an effect that has also be demonstrated in studies using mice. In addition, ketogenic diets may be effective in preventing oxidative stress brought on by caloric restriction and exercise in weight category related athletics, such as wrestling.
On the other hand, some researchers conclude that athletes should avoid a ketogenic diet altogether as it may be more harmful than helpful, especially for muscle recovery. Performance and recovery from exercise may be impaired on a ketogenic diet, due to reduced muscle glycogen and low blood sugar from lack of carbohydrates. As for athletes who participate in shorter anaerobic activities, like weight lifting, ketogenic diets appear to cause poor performance because there is less muscle glycogen stores available for quick use. It may take several months of adaptation to a ketogenic diet for glycogen stores to return to normal. A recent, small study found that a low carbohydrate, high fat diet reduced anaerobic exercise tolerance in subjects who were used to exercising, suggesting that a ketogenic diet should be avoided by athletes, especially those performing shorter, high intensity events.
At this time the results are still mixed, there is not enough information to come to a definitive conclusion for athletes. The ketogenic diet will continue to be a hot topic as more athletes experiment with ways to enhance performance through nutrition, and research uncovers more details about the long term impacts. At this time, a ketogenic diet may be more appropriate for casual exercisers because they tend to focus more on weight loss and not as much for elite athletes, who have more intense nutrition needs. As of now, it is best to proceed with caution and evaluate any diet change based on the type of athletic activity and overall goals.
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