Q&A: How Would the "Keto" Diet Affect My Training?

The ketogenic diet, keto for short, consists of a very low carbohydrate, very high fat, and moderate protein intake. It was first introduced in the 1920s as a treatment for children with epilepsy. The original diet restricted patients’ intake of carbohydrates to 15-20 grams daily. For perspective, there are more carbs in one medium-sized apple (25g).

Today, there are many iterations of the diet, but carbohydrate recommendations rarely go above 50g per day. In general, the keto diet recommends the following:

• Carbohydrates: 5-10% of total intake

   

• Fat: 70-80% of total intake

   

• Protein: 15-25% of total intake

   

The Academy of Nutrition and Dietetics (AND) recommends our diet consist of 45-65% carbohydrates. As I write this, I want to remind everyone, we’re not simply talking bread, pasta, and rice. Remember: Fruits and vegetables are carbohydrates as well, and they are loaded with micronutrients, antioxidants, and fiber. The point is that the keto diet is very carbohydrate restrictive—more than most, if not all.

Now that we know the basics of the diet, let’s talk sports performance. Should we, as runners, consider eating this way? I’m going to geek out in the science here for a bit, so hang on.

Going on a ketogenic diet means severely limiting carbohydrate intake. When the body doesn’t have enough carbohydrates available, it goes into ketosis—it begins converting fat into ketones. These ketones can then be used as fuel. Trouble is, our bodies prefer carbohydrates as fuel, especially during times of increased work, like, say, while running. 

The challenge then, of being a runner and going keto, is that you’re denying yourself the fuel your body favors during training. This can make a run, whether it’s two miles or 26.2, pretty uncomfortable.

At the end of the day, here are some things to think about before going keto:

Will you be able to run while on a keto diet? Yes.

Will it be fun? Probably not much.

Would I recommend it for runners? No.

Tiffany Chag is an exercise physiologist and registered dietitian. A fitness professional with more than 10 years of experience, she works with a diverse population of athletes focusing on improving sports performance through both strength and conditioning as well as nutrition. Chag received her Master of Science degree in exercise physiology and nutrition from Teachers College, Columbia University.