top of page

Is low carb low carb?

The story of the Tower of Babel is well known, famous and often referred to. A tower was being built that would reach into heaven. But this tower could not be completed because God had the workers speak different languages from one moment to another. Imagine a discussion about a topic where you think you are talking about vacation, using words that mean joy and pleasure to you. These same words however mean pain and misery to someone else. It will be very difficult to come to a consensus about vacation. To some degree this is what happens when people talk about low fat diets, high fat diets and their effects.

Source of confusion

The non-uniform use of terms has caused confusion and miscommunication in the popular press but also in the scientific community. The literature is full of terms that are not defined well enough and interpreted in different way by different people. There are many topics this applies to, but in particular to low carbohydrate, high fat diets. Terminology is confused. We talk about high fat diets, low carb diets, keto diets but we may be talking to someone who has different views on what "high fat" means, what "low carb" means and what a "keto diet" consists of. Very often I speak to athletes who are on a low carb diet supplemented with carbohydrate around training? Is this still low carb? In a recent paper we discussed this problem and called for scientists to sit together and come up with commonly accepted definitions that would help the confusion that is currently out there. For a link to the full paper click here.

Percentages versus absolute

Historically, even the scientific literature has provided confusing information. For example, carbohydrate needs were expressed as the ratio of energy contributed by carbohydrate in the athlete’s diet as the single metric of the adequacy of carbohydrate intake. A 50% carbohydrate intake for triathlete may be a whopping 1 kg per day and for a female gymnast as little as 200 grams. In the first case this would be a high carbohydrate intake, in the second one low carbohydrate intake, but they would both be classed as moderate intake. Clearly a percentage of energy intake is not a good way to express carbohydrate requirements. Therefore, carbohydrate requirements are usually expressed as grams per kilogram. In mainstream media we see these percentages still pop up.

Other ways to express carbohydrate needs

There are also many ways to express carbohydrate needs for athletes. For example, the term carbohydrate availability refers to the amount of carbohydrate available to do the work. If glycogen is depleted and no carbohydrate is ingested, carbohydrate availability is low and training in this state is referred to as “train low”. If we haven’t trained too much, we have eaten carbohydrate rich and we consume carbohydrate before and during training we are “training high”. Studies suggest that in order to get the effects of training low (for example changes in fat metabolism), carbohydrate availability needs to be low a certain level. However, in real life this is difficult to measure. So even for scientists it is not easy to define these terms and indicate exactly what is “low” and what is “high”.

Chris Froome's breakfast

Amplifying confusion

The press and social media amplify the confusion by mispresenting/misreporting sports nutrition research or practice and by generally oversimplifying the sophistication of contemporary sports nutrition knowledge.

Here is an example: In July 2016, Tour De France winner Chris Froome uploaded a photo of his breakfast on a rest day during the middle of this grueling stage race. This single picture of eggs, smoked salmon, and avocado caused an avalanche of claims and counterclaims about Froome’s advocacy of the low-carb high-fat diet, despite wider evidence presented by the athlete himself that he follows a plan in which carbohydrate availability is periodized according to his specific goals. Dr James Morton who works with this athlete and has written extensively on the general philosophy of “fueling for the work required”, as well as nutrition support for the Tour de France in particular, has worked with Team Sky for years and is also one of the authors of our recent paper. He believes that there is a role for lower carbohydrate intake on some days but very high intake on other days, especially those days when performance matters. Team Sky recently released data to illustrate the sophisticated periodization of body mass and energy/carbohydrate intakes according to the demands of each stage in a cycling tour, including estimates of Froome’s intake on the critical 19th day of his 2018 Giro D’Italia title: an astonishing 6,663 kcal (27.98 MJ) and 18.9 g/kg CHO (Check report here).

Keto adaptation

Another example: "keto-adaptation".... This term is used (or should I say abused) a lot! No one has ever defined it. I am not quite sure what it means or how it is measured... and so far no one has been able to explain it to me. Some people are quick to state things like "there wasn't enough time for "keto adaptation".... without knowing exactly what this means and without ways to measure it, it is impossible to make such claims! So, if we want to use such terms, lets define what they actually mean. let's determine how we measure them and then measure it! So that we can test the hypothesis! Without that this topic will remain in the domain of pseudoscience.


There will always be different views on a variety of sports nutrition themes, and some of this is healthy and important to move science forward. However, if these discussions are based on misunderstandings, different definitions or unclear terms, thus discussion is less than helpful and will not move science forward. Therefore, in the paper we ask both research scientists and practitioners to collaborate and share discussions, underpinned by a commonly accepted and consistent terminology. This will help to strengthen hypotheses and experimental/experiential data around various strategies. We also propose that athletes and coaches would be better served by less confusion and misinformation in all levels of literature.

With common definitions, evidence-based thinking, and a constructive attitude we might just have a fighting chance of complete the Tower of Babel one day.



Recent Posts

See All



If you want to find out  the best types of protein, optimal amounts, or timing. Click here 


Want to know more about nutrition for running. Click here.


If you want to know more about supplements, the benefits and the risks. Click here.

Sports nutrition

General sports nutrition topics can be found here.

bottom of page