Cleveland Clinic Journal of Medicine
https://pubmed.ncbi.nlm.nih.gov/?myncbishare=dukemlib&dr=abstract&otool=dukemlib&term=29634467
Many young women (and also some men) end up exercising and training so much, that they
burn more calories than they take in. They end up with an energy deficit from all of this exercise. In women, this can often lead to suppression of the menstrual cycle. Also a bone demineralization can occur, and these three items make up the female athlete triad.