Sign and Symptoms

Presentation
The defining clinical features are:

Deliberate weight loss with restriction of food intake.
Weight below 85% of predicted (body mass index below 17.5 kg/m2).
Have a dread of gaining weight and overevaluate their shape and weight.
Amenorrhoea for three months or longer (unless they are taking an oral contraceptive).

Eating and food behavior signs and symptoms
Dieting despite being thin – Follows a severely restricted diet. Eats only certain low-calorie foods. Bans “bad” foods such as carbohydrates and fats.
Obsession with calories, fat grams, and nutrition
Pretending to eat or lying about eating
Preoccupation with food
Strange or secretive food rituals

Appearance and body image signs and symptoms
Dramatic weight loss – Rapid, drastic weight loss with no medical cause.
Feeling fat, despite being underweight
Fixation on body image
Harshly critical of appearance
Denies being too thin

Purging signs and symptoms
Using diet pills, laxatives, or diuretics
Throwing up after eating
Compulsive exercising

Reference
http://www.patient.co.uk/showdoc/40000626/
http://helpguide.org/mental/anorexia_signs_symptoms_causes_treatment.htm