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Keto Diet

Ernst Peibst examines if the Keto Diet is good or bad for athletes.

Many gym-goers utilize ketogenic diets to try and lose weight. High fat and low carb diets are also common among athletes, with high-profile stars like LeBron James and Tim Tebow openly stating that they have incorporated the diet. Other celebrities such as the Kardashians and Halle Berry have also admitted to being advocates, with them often promoting different keto cookbooks. But, does going keto help or hinder performance?

There is no fixed answer for this, as each sport requires different levels of intensity and thus utilizes other energy sources. However, based on several studies, we have an insight into which sports are more suited to the keto diet.

Keto - Bad for Anaerobic Sports?

There is evidence to suggest that in some high-intensity sports, the keto diet may decrease athletic performance.

St Louis University tested whether the keto diet would be beneficial during anaerobic exercise. They had 16 men and women follow a high carb diet or a ketogenic diet, lasting for four days.

Researchers concluded that the participants following the keto diet had decreased athletic performance compared to the high-carb group. Results showed a dip in performance by 4-15% in comparison.

Thus athletes should be wary of adopting a high fat/low carb approach when regularly participating in high-intensity sports such as football (soccer), basketball, weight training, 100m sprint, rugby, swimming, boxing, and mixed martial arts.

Edward Weiss, a Ph.D. at St Louis University also found evidence in a 2017 review, that those incorporating the keto diet may be more susceptible to earlier fatigue during exercise. The surprising element in his findings was that he found this even in short-duration exercises.

Keto for Long-Distance Athletes

There is evidence to suggest endurance athletes who are exercising for hours at a time (at a low intensity) may benefit from following a keto diet. Dr Clifton Page says, "ketogenic diets appear to be beneficial for endurance athletes after a period of adaptation". Thus if athletes are going to adopt the keto diet, it may be worth doing so in the off-season so your body can slowly transition to using a different source of energy.

Zach Bitter, who is the definition of an endurance athlete, also vouches for the keto diet. He currently holds the record for the fastest time running 100 miles (in America)...and he did so without eating a single carb.

Zach has this to say about keto and athletic performance: "Fat is always the primary macronutrient in my diet. It can reach as high as 70% when I am recovering from a big race or workout."

By switching to keto, Zach says that he does not need to refuel as much during his races. He has stated that he has cut down his refuelling during races by a whopping 50% since going keto. Zach also claims that he does incorporate carbohydrates whilst at the peak of his training, but when he does, they will be low GI carb sources.

Examples of low GI food sources are:

  • Carrots
  • Chillies
  • Cabbage
  • Fruit
  • Lettuce
  • Milk
  • Oatmeal
  • Onions
  • Peppers
  • Pasta
  • Peas
  • Soya
  • Sweet potato
  • Wholewheat bread

Other Health Benefits of the Keto Diet

If you do participate in long-endurance activities and are thinking of switching to a keto diet, you can also look forward to the following health benefits.

Less Body Fat

This is not a guaranteed benefit, but more a common correlation. The reason why many men and women get leaner when going keto is that the diet suppresses your appetite; making you feel fuller for longer periods. This is due to a decrease in sugars in your diet.

As a result, you are less likely to snack throughout the day and crave eating junk foods as your blood sugar levels will remain stable.

Some experts believe sugar to be more addictive than cocaine. This is a controversial statement that has not been substantiated just yet, but we do know that sugar is addictive. So naturally, if you are eating less sugar in your diet, you are more likely to eat fewer total calories each day. Consuming fewer calories than your body burns each day will result in weight loss - which may be beneficial to an athlete depending on the sport.

Decreased Triglycerides

High triglycerides in the bloodstream increase the chances of heart attack and strokes. Although these are not common in athletes, unfortunately, they still happen. The good news is, ketogenic diets significantly reduce triglycerides levels.

Fat may be the most critical macronutrient here, as research also shows following a low-fat diet can increase triglycerides. High fat and low carbs seem to be the optimal combination.

Improved Cholesterol

Keto diets are also likely to lower your LDL cholesterol levels (the culprit for clogging up your arteries). Your HDL cholesterol levels (the right kind) are also expected to increase, lowering your blood pressure. Ideal ratios of cholesterol are beneficial for optimal heart health and blood flow, which may indirectly positively impact performance.

Page Reference

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  • PEIBST, E. (2019) Keto Diet [WWW] Available from: [Accessed

About the Author

Ernst Peibst is an ex-football player, playing for Salisbury City and Bath City. He is a big fan of weight training and has experimented with many different healthy diets.