Let the person know you are concerned about him or her. Reassure the person often that you love him or her for who he or she is.
Tell the person why you are concerned. Describe specifically what you have seen or heard is his or her behavior that concerns you. He or she can deny generalities, but will be less likely to deny specific dates, times, and behaviors you have observed.
Tell the person that food and weight are only part of the problem.
Become informed. Get information for yourself about signs, symptoms, and local resources and share it with him or her.
If the person is a classmate who won't get help; recruit others to talk to him or her. Enlist the aid of his or her parents, other family members, boyfriend/girlfriend, school counselor, etc. The person will probably get mad at you temporarily, but may later thank you for getting him or her help when he or she couldn't get it for him or herself.
If the person is your child and is younger than 18, get medical and psychological help immediately. People can die from eating disorders.
If the person is your child and older than 18, encourage him or her to talk to a therapist, counselor, or physician. Because he or she is a legal adult at age 18, the decision to accept or reject help will be his or hers.
When the person does decide to get help, provide moral support. If he/she wants you to, sit with him/her when he/she makes the first appointment, or go to the appointment with him/her.
Let the person know you have faith in him/her.
Don't nag, argue, plead, or bribe to get the person to discontinue the behavior.
Don't ignore the problem
Don't collude with the person by helping him/her cover up the behavior.
Don't hide food or stop buying food that others enjoy to prevent the person from bingeing.
Don't let tears, temper tantrums, or promises keep you from helping the person to get the help he/she needs.
Don't suggest weight loss or exercise programs.
Avoid describing food or eating habits in terms of good or bad.
Don't encourage perfectionism.
Don't put the needs of the individual with an eating disorder above your own.
I got this off RYL