I came across this article on the BBC website. I wonder how many triathletes suffer from this without realising it.

"(Red-S) occurs when sports people restrict their diet in the belief that constant weight loss will keep improving performance, to such an extent that some of the body's functions begin to shut down.

The condition can cause a range of health problems in men and women including a drop in hormone levels, a deterioration in bone density, a drop in metabolic rate and mental health problems."


https://www.bbc.com/news/health-46469538