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The Ketogenic Diet
Sarah Wright, BEST Triathlon Coach

For years, dietitians have been prescribing the ketogenic diet to patients as a form of disease management. Recently, athletes have started to catch on to the benefits of adopting a low carb, high fat diet that causes the body to enter a state of ketosis. This means the body is efficiently burning stored fat as fuel rather than sugars (carbohydrates) for energy.

What is the Ketogenic Diet?

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Ketogenic diet for triathletes

The ketogenic diet includes foods that are very low in carbohydrates and high in fat. Because of the lack of carbohydrates in the body, ketone molecules begin to build up and blood sugar levels decrease resulting in the body resorting to stored fats as fuel. Foods to avoid include grains/starches, legumes, fruits (small portions of berries are allowed), root vegetables (including potatoes, carrots, and sweet potatoes), diet foods, and alcohol. So what is left? A typical meal can include meat, fish, most vegetables, avocados, nuts and seeds and dairy. You must compensate for the reduced carbs by increasing fat content of meals since this is the body’s new fuel source.

Benefits of the Keto Diet

Why would you adhere to such a strict diet if not for medical reasons? The keto diet has been shown to reduce body mass, decrease blood glucose and insulin, improve insulin sensitivity, and increase “good” cholesterol(1). Additionally, it can result in weight loss without having to count calories due to meals being more filling(2). It is easier for people to eliminate food groups rather than having to keep track of calories and macronutrient intake.

Risks of a Low Carb Diet

The body stores carbohydrates in the form of glycogen. Glycogen can easily become depleted while on a low carb diet during training. Because glycogen holds up to four times its weight it water, the low carb diet can result in significant weight loss fairly quickly however it leaves the body with depleted glycogen stores and less water. During workouts, the body is now dependent on using fat as fuel, a process that is much slower than using carbs. Being in this state significantly impairs higher intensity workouts including weight training, track workouts, threshold, and interval workouts.
The Keto Diet and Athletic Performance

In a study found in Nutrition and Metabolism that tested elite cyclists on the ketogenic diet, it was discovered that there is a period of “keto-adaptation”. The body is adjusting to using fat rather than carbohydrates as fuel and as a result there is a decrease in physical performance for the first two weeks of the diet. After this time period, peak aerobic power and submaximal endurance performance were both restored to their original levels. It is also important to note that the VO2max of each athlete stayed the same throughout the 6 week study despite significantly limiting carbohydrate consumption (3).

Should I Try It?

As with most nutrition, it is very dependent on the athlete. What works for one person could be terrible for another. If you want to give the keto diet a chance, try it for 4 weeks and see how your body tolerates it. Ideally any nutrition experimentation would be done during the preparation or base phase of training to minimize risk of losing crucial fitness. Talk to your BEST coach about how to incorporate a low carb diet into your training!