Food and Behaviour Research

Donate Log In

13 August 2019 - Nutraingredients - Keto diet claims vs reality: What the science says

Nikki Cutler

keto diet

The keto diet is often not the performance boosting mechanism it is claimed to be, according to one expert.


The following research is referenced in this article:
See here for more keto articles

The keto diet is often not the performance boosting mechanism it is claimed to be, according to an expert who plans to set the record straight at NutraIngredients’ Sports Nutrition Summit next month.

The three-day event is set to investigate some of the biggest trends in the industry and answer burning questions on how different diets influence sports performance and how industry players can best meet the needs of these athletes.

Dr Mark Evans, postdoctoral researcher at University College Dublin, will explain how the keto diet has been touted as a way to take of advantage of the body’s large fat stores to fuel exercise for longer and improve exercise performance, however, it’s important to consider how intense that exercise is going to be.

What’s the keto diet?

In a sneak preview of his take at the summit in Amsterdam, Dr Evans explains that for a person to follow a ketogenic diet they must get 80-85% of their calories from fat, consume less than 50 grams of carbohydrates per day and the remaining 15% of their calories from protein.

“So it’s a very restrictive diet compared to the typical Western diet which is around 45-60% carbs and 20% fat.”

Dr Evans explains that the ketogenic diet is often falsely confused with a high fat diet which involves getting about 70% of your calories per day from fat but that diet is still not extreme enough to raise the levels of ketones in the body.

Why go keto?

Dr Evans explains that some people choose to follow the ketogenic diet as it has been claimed that the body can only store a certain amount of carbs which means we have a limited amount of energy stores.

Whereas if a person can reach a ‘ketogenic state’ then they will be able to take advantage of their fat stores and the argument is that they will have access to more energy.

“For example, an athlete may have 10 kilos of fat stored as adipose tissue and you’re talking 9 calories per gram of fat so that’s 90,000 calories worth of total fat in the body,” he explains. “But one issue with the arguments around keto diets is there is no consensus as to how to tell when a person has become fully adapted to a ketogenic diet.

“There’s no biomarkers universally accepted but there are some markers that people think indicate some level of keto adaptation, such as by testing the levels of ketones in your blood through a simple finger prick test.”

The science says...

Dr Evans argues that, based on the evidence so far, reaching a ketogenic status means you might not impair your performance at lower intensities of exercise but is likely to be detrimental to high intensity performance.

“When you do a high intensity workout, this is carbohydrate dependent and so if you are reducing your carb stores then you are inhibiting the pathways in the body to allow you to burn carbs. So, for for sports that include intermittent or repeated high intensity efforts like team sports and endurance sports, the keto diet is not currently recommended for exercise performance.”

Why the confusion?

Dr Evans believes a lot of the studies testing the use of ketone supplements on athletic performance have been confused with studies on people following a keto diet

“Our studies concentrated on raising ketone levels in the blood by supplementing the person with ketones which is very different to the person following a keto diet.

“They are still taking in a sufficient amount of carbs for high intensity performance but they are taking on supplements to elevate their level of ketones and this is a new way people are trying to improve performance.”

One such study by Dr Evans, found that a Ketone ester may have cognitive boosting properties that enable athletes to make crucial decisions during the final stages of a match.