Keto, or, the ketogenic diet and being in a state of ketosis has been a dietary buzz that has caught major tailwind in recent years. The diet has helped people lose significant amounts of weight in a relatively short timeframe, and its popularity has raised the interesting question that we thought we would uncover: how does a runner or endurance athlete fare in terms of performance when following the ketogenic diet?
  Fueling your body by burning fat - sounds wonderful, right? It is, depending on what your goals are.   [caption id="attachment_101193" align="aligncenter" width="684"]Keto Diet The ketogenic diet constitues a specific ratio between carbs, fats, and protein[/caption]  
What is the ketogenic diet?
The ketogenic diet is a high-fat, low-carb, sufficient protein diet, which studies and stories have found to be highly effective for weight loss. Here, the body burns stored fat instead of blood sugar and uses it for energy and fuel. The diet forces the body to burn fat instead of carbohydrates, which in turn results in rapid weight loss. This means that you will have to give up bread, pasta, and potatoes. In turn, you will find yourself slimming down quickly.   [caption id="attachment_101196" align="aligncenter" width="686"]Low carb veggies and fruits is a go-to on the keto diet Low carb veggies and fruits is a go-to on the keto diet[/caption]
How does this affect my performance?
The issue is, that the human body burns and uses carbs differently than it does fats, depending on the intensity of the training. A 2019 study from ‘’Medicine & Science in Sports & Exercise’’ analyzed the difference in a group of runners’ performance levels on a regular carbohydrate diet and a keto diet. When performing at below 60% VO2-max - the maximum threshold of your body’s ability to transport and use oxygen during physical activity - there were no signs of difference in performance levels among the diet groups. As we discussed a couple of posts back, aerobic conditioning is what you train when you run, row, hike, etc. At a higher intensity of aerobic capacity level (higher intensity training), the body switches to burning carbs for fuel. The body can break down and convert carbs to fuel much faster than it can fats. In other words: At a higher intensity of aerobic capacity, the body will have a difficult time keeping up on a keto diet compared to a sustainable intake of carbs. Indeed, the study found that the runners performing on the ketogenic diet had a decrease in performance levels of 5%. This further indicates, that higher intensity training - above 60% VO2-max - requires carbs for fuel.   [caption id="attachment_101205" align="aligncenter" width="685"]Depending on your goals, running on the keto diet could impact your performance negatively Depending on your goals, running on the keto diet could impact your performance negatively[/caption]  
Who should run on the ketogenic diet?
If the goal is to beat your PBs and reach new milestones, the ketogenic diet will negatively impact your results. The diet does not allow for a sustainable amount of carbs to fuel the body. The body cannot sustain the fat and convert it to energy at the same effective rate as carbs when performing at maximum capacity. This means, that you will have a harder time pushing yourself to reach those performance levels. However, the negative impact only applies if you truly are an athlete or endurance- and ultrarunner. You need to push your body intensely for the keto diet to affect your performance levels, and you have to run very far for the diet to affect you negatively. If you are more of a casual runner looking to stay fit and healthy, and possibly even lose some weight, then following the keto diet might be the choice for you. You have to decide for yourself what your goals are and what you wish to achieve. If you wish to run below maximum capacity and burn fat at a higher level, then the keto diet is a perfect solution.  
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