Applied Sports Nutrition Support, Dietary Intake and Body Composition Changes of a Female Athlete Completing 26 Marathons in 26 Days: A Case Study A British group has investigated the nutritional behavior on a runner who runs a marathon during 26 days every day. During the marathons she took 1039.7 ± 207.9 kcal (607.1 - 1453.2) and 2.39 ± 0.35 l (1.98 - 3.19).
After 11 days, body weight decreased by 4.6 kg. All details can be found under https://pubmed.ncbi.nlm.nih.gov/28344459/