Anorexia nervosa

Anorexia nervosa is an eating disorder. People living with it restrict what they eat: they take in less energy than their body needs, and that restriction drives their weight down to a significantly low level.

It is not just about eating too little. It comes with an intense fear of gaining weight and a distorted body image, meaning a perception of one's own body that does not match how it actually is. It is like standing in front of a mirror that reflects a body different from the one standing there. The brain changes too: there are deficits of dopamine and serotonin, two chemical messengers neurons use to communicate, and changes in the circuits tied to appetite, fear and habits.

Meanwhile, the rest of the body bears the burden of prolonged starvation, which means going a long time with less food than the body needs, and of purging behaviors, the ways of getting rid of what was eaten. Multiple complications are tied to them, such as bradycardia, a heart that beats more slowly than usual, or osteoporosis, bone that becomes more fragile.