Despite the recent popularity of low carb and ketogenic diets and the growing number of nutritionists and dieticians who support them, many still doubt their effectiveness. This is especially the case when it comes to athletes. Where many health professionals still hold on to the old idea that “athletes need to eat carbs,” recent studies show that may not be the case. In fact, research shows that a low-carb or ketogenic diet may not only allow athletes to train and perform at their best, but may also provide some medical benefits for athletes and non-athletes alike. 

Numerous scientific studies have been carried out by different researches between 2012 and 2018 to determine the effects of ketogenic diets on the performance and overall health of various athletes. Each of the studies took place over 2 to 12 weeks while researchers documented various aspects of performance such as speed and strength as well as the athlete’s body composition in groups that did and did not follow ketogenic diets. What did they find out? The results may surprise you.

Endurance athletes

Athletes who ate a low-carb ketogenic diet for 3 months showed improvements in peak power and body composition compared to the control group.

CrossFit Athletes

At the end of a 12-week study, athletes who followed a ketogenic diet had a decrease in fat mass and either improved or maintained their performance in running, weightlifting, and aerobic performance. 

HIIT Athletes

HIIT athletes on ketogenic diets not only maintained their overall performance, but experienced an increased ability to utilize fat over time.


Triathlon athletes who consumed a ketogenic diet for 5 weeks showed a V02 improvement of 45% PPO as well as a decreased body fat percentage with no change to their lean body mass.


Olympic Weightlifters

Weightlifters who aimed to reduce their weight were able to do so while following a ketogenic diet for 3 months. While their weight decreased, their performance remained stable, essentially increasing their power-to-weight ratio. 


Gymnasts on a 3-month ketogenic diet showed no change in performance from before the 3-moth period. Athletes did, however, lose about 5 lbs of fat while maintaining their muscle mass. 

A ketogenic diet may offer long-term health benefits as well. A 2016 study monitored the glucose levels of sub-elite athletes who consumed a diet high in carbohydrates, including a lot of added sugar. The study found that, while the body composition of the athletes showed they had a low body fat percentage, 30% of the subjects had blood sugar levels that were pre-diabetic. So while carbohydrates and sugars may not have an obvious negative effect on athletic performance or health in the short-term, it may be contributing to factors that could lead to significant health problems down the line.

While some dieticians and scientists may continue to support the narrative that athletes need sugars and carbs for optimum performance, and may even claim that sugar doesn’t have a significantly harmful effect on an athlete’s heath, the evidence strongly suggests otherwise. For athletes, a low-carb or ketogenic diet may not only have short term benefits for their performance or body composition, but could have a long-term impact on their overall health and ability to keep competing.