RED-S is a potentially serious issue in sport, especially endurance sport. The Mindset of Light = Fast, something I have fallen into myself, increases this risk. After recently purchasing some old copies of Like the Wind (running magazine) I started to look into it a bit more as many of the symptoms listed are little things that have been bothering me recently. I will start by saying that I don't think I am at a high risk of it, I have been careful to eat a lot and my weight loss has been slow and steady with many stalls. Nonetheless I am probably at a higher risk due to my highly competitive nature and background of obesity and not believing that I am now sim, despite everyone telling me that I am. So I suggest you check out the many great online resources around RED-S and look after yourself. In short it is a condition caused by overtraining and under eating, it is far too complex and ill defined for me to say much more than Goolge it and be aware of it.