Athletic Performance and the Ketogenic Diet

A ketogenic diet (KD) refers to any dietary pattern that results in the body being in a ketogenic state of metabolism. Most classically, ketogenic diets are high in fat, moderate in protein, and low in carbohydrate. The idea is that by following this dietary pattern, the body will adapt to use fat as energy more readily instead of glucose – our primary fuel source. (1)

Due to this concept, it is easy to see why the KD has received recent popularity amongst people trying to alter their body composition and even amongst athletes looking to enhance their performance. The KD, however has not been extensively studied specifically in athletic populations. To date, the only extensively researched benefits of the KD (and its variants) are within the treatment of epilepsy and other seizure disorders. (1)

For athletes specifically, the research does not support the efficacy of the KD in those engaging in high intensity sports. The transitionary period into a KD can be cumbersome for athletes as well – taking multiple weeks to adapt, with still minimal reported benefits.(2) The best approach for fueling high performance individuals continues to be a well balanced, consistent, and carbohydrate based diet. In fact, using fat as energy requires more oxygen use and in the long-term can decrease sustained performance. Some athletes, however, may find benefits from “training low [carb]” a few times per week so long as they are generally fueling adequately for other workouts and daily activity. (3)

Risks of adopting a strict KD include: hypoglycemia (low blood sugar), decreased energy and mental function, decreased athletic performance, gastrointestinal discomfort, and risk of nutrient deficiencies if not carefully managed.. For those with a history of metabolic disorders that limit fat metabolism, the KD should absolutely not be followed.(1) If you are considering a true ketogenic diet or seeking dietary modifications to improve your health and/or performance, please consult with your medical care team, including a Registered Dietitian (RD).


Roehl, Kelly, and Sarika L. Sewak. “Practice Paper of the Academy of Nutrition and Dietetics: Classic and Modified Ketogenic Diets for Treatment of Epilepsy.” Journal of the Academy of Nutrition and Dietetics 117.8 (2017): 1279-1292.

Thomas, T at el. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine: Nutrition and Athletic Performance. J Academy of Nutrition and Dietetics. 2016; 116 (3):501-28

Burke L et al. Low Carbohydrate, High Fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. J Physiology, Dec 2016 (open access; read at

Author: Christina Figueroa MS, RD, CSSD, LDN – Sport Dietitian
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