How Keto Can Affect Running Performance

Athletes have begun to experiment with the new “Fat for Fuel” eating habits called the ketogenic diet. It’s not a new diet. Doctors have been using it for decades to treat epilepsy in children, reducing the amount of seizures they have; and also for another range of neurological diseases. Everyone’s been asking though if it works for runners, what exactly it does, and if it really is worth the hype? Let’s break this all down. 

WHAT IS THE KETO DIET

The keto diet is an extremely high-fat, low-carb diet with a balanced amount of protein. The goal of the diet is to put your body in a state of ketosis. This metabolic process kickstarts when your body does not have enough glucose (sugar) for energy. Your brain will then signal to the liver to break down fat to release ketone bodies for fuel. This is a normal physiological process that your brain indicates naturally. What we don’t know are the long term effects of this diet and whether or not it’s safe to toy with your metabolism in this way. Getting your liver to go through this process is the tricky part of switching to “ketosis” mode.

This state is usually achieved when your body is in the case of starvation or in the minimal presence of carbohydrates, conditions which are unpleasant and difficult to sustain. A significant carbohydrate restriction is required,  with no more than 50 grams of carbs per day (let’s take note that a medium-sized banana already puts you at 27g for the day). Ketosis does not occur in a few days, depending on the person it can take up to a week for your body to turn the switch. 

WHAT FOODS ARE NORMALLY ALLOWED

While on keto, foods high in fat are more than 50% of your diet. Keto dieters eat lots of salmon, avocado, nuts, and beef. Fruits are typically very restricted because they are so high in sugars, but berries are usually allowed in very small doses. Vegetables you have to be careful with, the secret sugars can fool you. For example, one cup of chopped broccoli already puts you at 6 carbs, 12% of your daily carb consumption. It’s better to stick to dark leafy greens such as spinach, asparagus, zucchini, and celery. 

KETO FOR RUNNERS: HIT OR MISS?

So why are athletes hinged onto this if there are so many restrictions? Here’s a fact to take into consideration. Our body’s energy reserve can only hold about 1600-2000 calories worth of carbohydrates in the muscles, blood, and liver. The switch to fat, therefore, entails no limit since our body has an unlimited amount of fat storage space. This means the inevitable wall that gets hit around mile 16, due to low blood glucose, theoretically no longer will exist. So although these ketones may have a promising source of fuel for endurance runners, metabolic ketosis has limitations that makes it difficult to recommend to athletes. 

A study performed on athletes who were strictly following a high-fat low-carb diet showed to have impaired performance. What happens with fat oxidation, there is an increased demand of oxygen to keep up with the demands of running. This does not necessarily cause a problem since you have more energy stored to keep up with the high demand, but it does not promise an increase in performance either. 

More studies have been conducted and failed to detect clear benefits during endurance training. There may be a few scenarios where a keto diet would show improvements in training sessions, but it is not a scientifically proven claim. Within the last five years, more research has suggested performance impairment because of the body’s low glucose levels. Carbohydrates are a key fuel source for skeletal muscles during intense training sessions, depriving them of this causes your body to therefore work harder. Overall, there is currently just not enough information on the actual effects of ketone bodies on exercise metabolism and performance in runners. 

So, at least for now, the sports medicine community has not yet come to a conclusion whether keto can actually help runners or not. If you are geared more towards a weight-loss goal, keto will definitely help with that. If you are looking more for a performance enhancing way of eating, consult with your nutritionist to test out what can work best for you. 

https://trainright.com/should-endurance-athletes-go-keto-ketosis-ketogenic-diets-for-endurance-athletes/ 

https://www.ncbi.nlm.nih.gov/pubmed/28012184 

https://www.ncbi.nlm.nih.gov/pubmed/26553488 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5309297/ 

https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.976.601&rep=rep1&type=pdf 

http://runspi.com/wp-content/uploads/2015/01/Marathon_Nutrition_Guide.pdf