Anorexia athletica, the compulsive and excessive use of exercise to maintain an abnormally low body weight, is not a formally recognised mental health disorder. It is not something doctors diagnose in its own right, and when I speak to one psychologist about the condition, she declines to use the term but is happy to speak about its ramifications.

Yet look online and it’s a different story. Blogs, forums and other social platforms discuss the affliction, also known as hypergymnasia or sports anorexia. On Instagram, more than 2,000 anorexia athletica hashtags are attached to posts of people clothed in Lycra, running and holding energy shakes. On forums, others discuss anguish at missing workouts. On myproana.com, a site for recovering anorexics and their families, one daughter laments a mother who exercises six hours a day. “She says that exercise is like breathing to her… she’d suffocate without it.”

Exercise is a healthy pursuit, but problems arise when it becomes something else. When taken to extremes, it can lead to anaemia, arthritis, heart problems, memory issues, poor body development and infertility. It can even prove fatal through heart or kidney failure.

Natalie Lawrence, a mother-of-two from Bedfordshire, knows only too well the physical repercussions of anorexia athletica. Eight years ago, she was diagnosed with osteopenia, a precursor to osteoporosis, caused by an addiction to exercise.