We just talked about low-carbing or fasting before workouts. How about going low carb for a few months? For life?. Enter the ketogenic diet.

By significantly reducing the amount of daily carbohydrate intake (<50g), we go into a state of ketosis, where our body utilizes fats and ketones as your primary fuel source. Sounds similar to the fasted cardio method, but this takes an athlete several weeks to become fat-adapted, therefore affecting exercise and body composition on the longer-term. Is it useful? Is it effective?

We can look at it from different angles:

Keto for someone looking to lose weight:

In this situation, we have to take into consideration their ability to sustain a diet with low-carbs. Many of the foods today world contain carbohydrates and it is often hard to skip meals with your friends and family. Consuming a bit too many carbs can bring you out of ketosis and make you feel worse. You don't want to be in no-man's land - where you're not consuming enough carbs to fuel your daily life and exercise, and where you're consuming too many carbs to be in a ketogenic-state.



Diet sustainability is a big factor, paired with the fact that trainees still have to be eating in a calorie deficit. Knowing what fat and protein sources to eat is also something that must be learned if a keto diet is to be sustained in a healthy manner. Many people can't effectively lose weight and keep that weight off with a ketogenic diet. The ones that can, great for them. Find what works for you in terms of weight loss. I recommend reading or buying "The Ketogenic Diet" by Lyle McDonald, he has written extensively on this topic and how to properly go on a ketogenic diet for fat loss, performance and body composition goals.



Keto for a competitive athlete:

Jeukendrup's review paper and numerous other studies state that a keto athlete has dramatically increased fat utiliziation ability and upregulated enzymes involved in fat oxidation. However, some of the same studies that showed there was no improved performance effects regardless of the fact fat oxidation potential was increased.

There are a lot of successful keto athletes though, it just depends on the type of sport.

Like I alluded to earlier, exercises or sports that utilize lower heart rates and intensities will pair best with a low-carb method or approach. While fat isn't a quick source of energy like glucose and phosphocreatine is, it can provide a lot of energy, 9kcal/g. This is viable for sports that are low intensities in nature but require a lot of energy, such as ultra-marathons and other long endurance events.

This is not to say a calorie-matched high carb diet won't be more beneficial. Ketogenic athletes have shown to have a reduced ability to utilize carbohydrates as the enzymes related to carb metabolism are compromised when going on prolonged periods of carb restriction. Not so great for many team sports or endurance events that require repeated short bursts of high-intensity.

edit: A 2017 study looking at race walkers on a ketogenic diet showed reduced economy, impairing performance. <Study here>

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