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Ketogenic Diet for Combat Athletes

There are so many diets going around, all of them with their own army of adherers. They will defend their diet religiously against any argument with a counterargument. One of those diets is the Ketogenic Diet. 

The ketogenic diet is gaining notoriety fast. I've followed it myself for a couple of months, with remarkable results. There are many proven benefits to the diet. But is this way of eating also suitable for a competitive fighter?  Combat sports like MMA, Muay Thai, Wrestling, BJJ,... have their own specific requirements and characteristics.

The Ketogenic Diet

The ketogenic diet limits the consumption of carbohydrates to a minimum (< 10% of daily calories), while increasing fat intake (>65% of daily calories). No more pasta, bread, potatoes or rice. Because of the lack of carbohydrates in the system, the body will use fat as its primary fuel source. When this happens, your body goes into 'ketosis'. 


There are many benefits of the ketogenic diet that have scientific backing. Some of these could be especially interesting for fighters:

Weight and fat loss. 

For athletes operating in weight class-based sports, like most martial arts, it’s important to keep their weight in check. The ketogenic diet has been shown numerous times to induce weight loss. [1,2,3

First of all, when starting the diet, you’ll notice you’ll lose weight very quickly. These first kgs you lose are a result of a loss of water in the body. If we restrict carbs, the amount of glycogen in the body reduces as well. Glycogen holds on to water. During the first phase of Keto, water is released together with glycogen. This can result in up to a loss of 4 kg. These kilos, however, will be put on again, as soon as the person starts eating carbs again. This attribute makes the diet perfect to put on weight again after weigh-ins. 

Next to weight loss in the form of water loss, the diet also results in fat loss. However, there is no consensus as to how the diet actually achieves this fat loss. Some say, that because of the restriction of food options, the dieter will eat fewer calories in total. If this is the sole reason behind the weight loss effects of the diet, the ketogenic diet would work in exactly the same way as other diets, by restricting calories. [4,5]

Others say that the ketogenic diet is, in fact, superior to other diets for fat loss, because of two reasons: 

  1. The diet is supposed to reduce hunger by reducing ghrelin in the body, the ‘hunger hormone’. More ghrelin is correlated with more food intake. In other words, when on a ketogenic diet you are more likely to restrict your calories because you are not as hungry. [6,7]

  2. The diet has been shown to reduce insulin in the body. This finding is not surprising as Insulin is released as a response to carbohydrates intake. Insulin is a hormone that aids in fat storage. Many people link these two scientific findings together and conclude that people on a ketogenic diet will store less fat than people on another diet, even when calorie intake is equal. However, we have found no research that supports this last claim.

Reducing Inflammation

Claims have been made that the ketogenic diet reduces inflammation in the body. Inflammation is a natural response to an injury or to excessive stress to the body. The inflammation defends the body against infection and promotes healing. But when this response is triggered constantly, because of heavy training for example, you could get chronic inflammation. When it is chronic, it becomes damaging instead of protective. Chronic inflammation can be a cause of a wide arrange of problems, e.g.: fatigue, joint pain, gut problems, etc.

Considering the hard and strenuous training of combat athletes, it would be wise for them to have some strategies to keep inflammation in check. 

There has been done limited research on the anti-inflammatory effects of a ketogenic diet. The little research that has been done, was done on rats and only consisted of two studies. They did find a positive effect of the diet on reducing inflammation in the body. However, I wouldn’t go as far as to use these studies to argue that athletes should go on a ketogenic diet. [8,9


The ketogenic diet has grown tremendously in popularity. In the last five years, many people have followed it and sprayed the internet with their personal testimonials. The testimonials online, which describe how the diet has caused miraculous changes in their lives, are endless.


But testimonials of professional athletes who claim that the diet has increased their athletic performance, are very rare. Reason being that the ketogenic diet simply is suboptimal for athletic performance. This has been confirmed by a number of studies. [10,11,]

  • Anaerobic exercise

And when we do find such a rarity it comes from ultra-endurance athletes. 

Zach Bitters, a top-level ultra-runner, states in the interview below that the bulk of his diet consists out of fat:

 “Fat is definitely the foundation of my nutrition. ” 

Zach is one of the most successful ultra-runners of the last decade. He holds the record for the fastest 100 mile run and for the longest distance run in 12 hours. But even he states that he will always consume carbohydrates when he’s in a big race. Reason being that carbs are simply a more efficient fuel source.  It requires significantly more oxygen to generate energy from fat in comparison to carbohydrates. [12]

But when he’s not competing, most of the days he follows a low carb high-fat diet, even when training. Running on this diet, trains his body to use fat efficiently as a fuel source.  The result is that in a race, he won’t bonk when his body runs out of glucose. That being said, depending on the combat sport, the fight will take place anywhere between 8 and 30 minutes. Since the body can store enough glycogen for at least two hours of hard exercise, bonking because of a lack of glucose isn’t even an issue for fighters. 

  • Aerobic exercise

Furthermore, fighters, from all combat sports, have very different requirements as ultra-runners. Whereas long distance running is almost exclusively anaerobic, combat sports are both anaerobic and aerobic. Fighting involves a lot of ‘explosions'. Punching, kicking, going for a takedown, defending a submission,... they all have to be performed as fast and as powerful as possible. Speed and power are absolutely crucial in combat sports to become successful. Here, we really come across an unforgivable characteristic of the ketogenic diet.  When you are on the ketogenic diet, you have little to no glycogen available for conversion into ATP. ATP is what gives the muscle the energy to contract. The conversion of glycogen into ATP is a lot faster than the conversion of ketones into ATP. So, we could say that without stored glycogen in the muscles, your ‘explosions’ won’t be as fast and as powerful.

It’s essential to have this explosive power in training as well. You have to be familiar with what you are capable of and how you will perform when in competition.


The limitations that the diet poses on aerobic exercises, make the diet not suitable for combat athletes. Not in competition and not during training. The only time that following the makes sense, is during a weight cut. The fast water loss makes the athlete reach the desired weight easier and faster. After the weigh-in, the fighter will put back on weight when eating carbs.

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