A faster running speed is associated with a greater body weight loss in 100-km ultra-marathoners. Generally, it is known that slow marathon runners drink more and tend to tend to hyponatemia. Furthermore, there is the opinion that it has to prevent dehydration with a perseverance burden due to a lot of drinking.Ultralauf seem to tackle something different. At 219 100 km runners showed that the fast runners drank more than the slow runners, a lower liquid supply to a decrease in body weight and the runners obviously ran faster when the body weight is accepted.
This contradicts the previous opinion, you have to drink as much as possible in endurance loads and that only the slow runners drink a lot. The practical meaning is that even with very long stresses, it is possible to drink until little to little and that the weight loss can even improve the mileage. Details below https://pubmed.ncbi.nlm.nih.gov/22668199/