*sigh* Oh dear.
Anorexia is um, mostly I think, psychological. It's the utter inability to see the reality of what size you are, in relation to 'healthy'. Like, from talking to friends, there is no too thin. There just isn't. Some of it's competition, some of it's taking control back, some of it's punishment, some of it is obsession. Different for different people.
Obesity. Most psychological, but there are other reasons. Go do some research on thyroid problems, insulin resistance and polycystic ovary syndrome. Between 1 in 5 to 1 in 10 women in thought to have polycycstic ovary syndrome.
Fat does not always mean eating too much. Sometimes it means lack of education, lack of understanding of calories, ignorance of in=out, restrictions on mobility preventing exercise, fear of being laughed at stopping people exercising and sometimes, just sometimes, it's a result of an almighty mess up in the way a body functions. Thankfully, the NHS is a bit more clued up than some of you these days so it's getting sorted 😆 Most of my mates with PCOS seem to have taken a sudden interest in biking. Can't think why.