The following is for you if you are much under the weight you are supposed to be because you have chosen to eat very little:
First of all it is necessary to know why you eat so little and have chosen to starve. Think about how you feel nowadays and how you would feel if you ate more. You will then notice that starvation gives you a feeling of security concerning yourself and you are afraid that eating more would take this away and you would become anxious and worried.
Compulsive eating and vomiting is used in the same way by some people. They create a false feeling of satisfaction and control - they enable the real internal feelings to be avoided.
In psychology this is called using starvation as a defence mechanism i.e. you defend yourself against your internal worries by starvation. Starvation fills a similar function for you as alcohol does for the alcoholic and drugs for the drug addict. These are substances which reduce anxiety and create a false feeling of contentment.
By using starvation to repress unpleasant feelings you hinder yourself from acting on your internal needs and constructively understanding and learning to manage your problems. Psychotherapy helps us to be open for our internal thoughts and sensitive to all feelings in our inner world. This means that psychotherapy has a greater chance of success if you stop suppressing your feelings by starvation. It is similar when using psychotherapy on drug addicts: it is impossible as long as the drug addict uses drugs to suppress feelings.
Starvation and underweight can also cause you to function badly in other areas e.g. at work or school. It can even cause illness and in some cases lead to a patient's death.