The Interconnectedness of Diet Choice and Distance Running: Results of the Research Understanding the NutritioN of Endurance Runners (RUNNER) Study. A recent study examined 422 runners about half marathon, marathon and ultramarathone with respect to their diet in the 12 months before a competition.Ultralaufen preferred a vegan / vegetarian diet as a half marathon or marathon runner.
The Ultralaufen mentioned that primarily the external circumstances resulted in this diet, while the half marathon and marathon runners rather performed body weight as a reason. The interesting work can be found under https://pubmed.ncbi.nlm.nih.gov/26480477/