Alex Hutchinson reports on a new study that challenges common wisdom about losing weight in an endurance event. It is widely believed that it's a sign of dehydration when you lose weight during a run. However, when you burn fuel during exercise, e.g. carbs stored in your muscles, the chemical reaction releases stored water for use in your body. Thus, according to this study, you *should* lose a little weight when you run because you're using up fuel. However, your level of hydration may not decrease unless you lose a larger amount of weight.
https://www.runnersworld.com/sweat-science/just-be...