There is zero evidence that keto or low carb/high fat diets improve running performance. There's actually consistently reproduced evidence that it impairs performance at high intensities. Studies: https://physoc.onlinelibrary.wiley.com/doi/10.1113/JP278928, https://pubmed.ncbi.nlm.nih.gov/16357078/, https://pubmed.ncbi.nlm.nih.gov/26553488/, https://pubmed.ncbi.nlm.nih.gov/32497061/
Summary if you don't want to read all the studies: https://trainright.com/should-endurance-athletes-go-keto-ket...