Lack Of Self-Acceptance
The main cause of anorexia is lack of self-acceptance. Anorexia is a deliberate long starvation exercise mainly in order to reduce weight and look thin. Incidentally, an anorexic even when already thin has this devastating passion to go for more thinning spree.
The lack of self-acceptance gives rise to false self-image. In this, you look at the mirror and see something entirely different from what you really are. Each look at the mirror gives the same false image, sometimes even a worse picture.
Fat = Ugly, Thin = Beautiful
There's also this belief that fat is UGLY and Thin is Beautiful. Therefore, everything to push the thinning process is fully put in place. Overeating processes and the result of fatness could make you hate foods and eating. What is eaten, if at all, is weighed in terms of what calories it adds and not what nourishment it gives. Therefore, it is bad and not to be eaten if it crosses a certain calorie content level. As a result, an anorexic eats little or nothing daily. And feels very comfortable about it.
Extreme Exercise Regimen
As if this is not bad enough, you add a rigorous exercise regimen to burn whatever calories you suspect you gained. The exercise is extreme and often anaerobic. In an anaerobic exercise, oxygen is used up easily. A breakdown results. You may not feel deterred because you have a set goal to thin out. This cycle becomes a daily pattern. Eat little or nothing daily.
Pretend before family and friends that you eat well and that you are okay. Consequently, you avoid eating with them. And even avoid hanging out with them. When you move from hunger pangs to non at all, no matter the starvation level, there's danger. Anorexia is already at work. The restlessness, the headaches, the thinning out of hair, the dizziness, the irritability, the nausea and more are all warning signs that anorexia has set in and that the deadly anorexia crisis is at the corner.
It is clear that the cause of anorexia eating disorder is hinged on your inability to accept yourself and who you are, your inability to take responsibility to care for you and your body.
You could do something positive about it.