This question is about Nutrition and Running
The keto diet is not advisable for runners, as it may hinder overall performance [1]
The keto diet is a high fat, low carbohydrate diet that consists of less than 50 grams of carbs per day. Carbohydrate is the primary fuel source for working muscles, and severe restriction appears to have a negative impact on endurance performance [2]
The keto diet has two big downsides for runners: limited glucose availability and increased oxygen demands. Although fat burning increases following a keto diet, endurance capacity in keto-adapted athletes still appears to be limited by glucose availability [ 3 2
Despite increased fat burning, endurance capacity in keto-adapted athletes still appears to be limited by glucose availability [ 3 2 3
Kerksick, C.M., Wilborn, C.D., Roberts, M.D. et al. ISSN exercise & sports nutrition review update: research & recommendations. J Int Soc Sports Nutr 15, 38 (2018). https://doi.org/10.1186/s12970-018-0242-y
Burke, L. M., Sharma, A. P., Heikura, I. A., Forbes, S. F., Holloway, M., McKay, A., Bone, J. L., Leckey, J. J., Welvaert, M., & Ross, M. L. (2020). Crisis of confidence averted: Impairment of exercise economy and performance in elite race walkers by ketogenic low carbohydrate, high fat (LCHF) diet is reproducible. PloS one, 15(6), e0234027. https://doi.org/10.1371/journal.pone.0234027
McSwiney, F. T., Doyle, L., Plews, D. J., & Zinn, C. (2019). Impact Of Ketogenic Diet On Athletes: Current Insights. Open access journal of sports medicine, 10, 171–183. https://doi.org/10.2147/OAJSM.S180409