We are not allowed to write the statement for you but we can help you learn how to write the statement.
A thesis statement is going to have many elements that will explain to the reader what he or she is about to read. It is usually a single sentence in the beginning of your paper. It will be a direct statement that shares how you feel about the subject.
Your thesis statement should also be a statement that some people may disagree or agree with. You will address a topic and ask a question regarding anorexia nervosa and your thesis statement will include the answer to that question.
Below is an excellent link that contains a great amount of information about how to write a thesis statement in detail.