The Effects of a Ketogenic Diet on Anthropometric Parameters, Metabolic Adaptation, and Physical Fitness Performance in Amateur Endurance Athletes: A Systematic Review

Implementing ketogenic diets (KDs) in endurance athletes is currently an interesting topic. This article aimed to systematically review the effects of KDs on anthropometric, metabolic, and performance parameters in endurance sport athletes, highlighting the recommendations about how they should be used. This systematic review was performed under Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, and it was performed using 2 databases (i.e., PubMed and Web of Sciences). From the 1,485 studies initially identified, 14 were fully reviewed, and their outcome measures were extracted and analyzed. Regarding anthropometrics, KDs (i.e., daily caloric intake of carbohydrates [CH] < 5%) can lead to a reduction of body weight and percentage fat mass, with a possible impact on maintenance of fat-free mass. Regarding the metabolic adaptations, KDs lead to glycogen storage and fat mobilization, specifically, when using daily caloric intake of CH less than 8%. However, no positive or negative physical fitness and conditioning effects have been found when using KDs. In conclusion, although KDs could be a suitable strategy to induce anthropometric and metabolic changes, this type of diet could not be suitable to improve amateur endurance athletes' performance.