There is a growing interest in high fat diets within the athlete community. Why the interest? Eating a high fat, low carbohydrate diet teaches the body to rely on fats as a fuel during exercise, rather than the carbohydrates that are stored in our muscles and liver. Teaching our body to use fat rather than carbohydrates is of interest because fat stores are pretty much unlimited in the body, even for the skinniest athletes. On the other hand, carbohydrate stores are very limited. Any athlete that has “hit the wall” can attest to this.

 Teaching the body to use fat as a fuel source means that athletes wouldn’t need to rely on gels, Gatorade and other carbohydrate sources during exercise. We all know that gels can be a big pain in the butt. Not needing them sounds too good to be true. However, this increased reliance on fat rather than carbohydrates does come at a cost: performance. High intensity exercise requires carbohydrates. We simply cannot exercise as hard when using fat as a fuel source compared to carbohydrates.

 Bottom line, if your goal is to perform at your best, such as hitting a personal best time in a marathon, then a high carbohydrate diet is the way to go. Let’s take a look at Kenyan athletes. We all know that they dominate in endurance events. Studies have shown that they eat an incredible amount of carbohydrates. Trust me when I say, it’s A LOT.  If they were to switch to a high fat, low carbohydrate diet, they’re performance would almost certainly be compromised as their ability to compete at a high intensity would drop. Carbohydrates are the high-octane fuel source.

 I do think that high fat, low carbohydrate diet could be used successfully for some athletes. These would be athletes less concerned about performance time and more focused on getting across that finish line. Another group that may benefit is ultra-endurance athletes. For instance, some ultrarunners who compete for days have found success using the high fat approach. This is because they are running at a slow steady state and as a result, use a larger proportion of fat as a fuel source rather than carbohydrates.

 If you do decide that the high fat route is the best approach for you, proceed with caution. Following a high fat diet would mean cutting out high quality carbohydrate food sources such as fruit, some vegetables, whole grains, milk and yogurt. These are also valuable sources of some important nutrients and cutting them out does put you at risk of deficiencies. I would suggest working with a Registered Dietitian with experience in sports nutrition to ensure that your diet is still adequate and health won’t be compromised.

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Categories: Megan Kuikman

Megan Kuikman

Hello! I’m Megan Kuikman. I’m a Registered Dietitian with specialized training in sports nutrition. My goal is to help athletes and active individuals achieve a healthy attitude towards health, training, and food. I empower athletes to fuel properly for training in order to restore their health and enhance performance. You can get in touch with me at:


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