OBJECTIVE This study tested the reciprocal relationships between automatic thoughts about eating and the actual-ideal weight discrepancies, and their role in the formation and maintenance of eating disorders (ED) symptoms in a non-clinical sample of adolescents. In particular, we investigated whether thoughts about eating mediated the effects of weight discrepancies on ED formation and whether weight discrepancies mediated the effects of thoughts about eating on ED formation were investigated. METHOD Data were collected three times, with a 2-month interval between Time 1 (T1) and Time 2 (T2), and a 9-month interval between T2 and Time 3 (T3). Adolescents (N = 55) aged 15-18 filled out the SCOFF Questionnaire, assessing eating disorders symptoms, and the Eating Disorder Thoughts Questionnaire, evaluating automatic thoughts. To assess weight discrepancies questions about actual (subjectively reported) and ideal body weight were asked followed by objective measurement of height and weight. RESULTS Negative thoughts about eating (T2) mediated the relation between weight discrepancies (T1) and symptoms of anorexia and bulimia (T3). In addition, the association between negative thoughts (T1) and eating disorders symptoms (T3) was mediated by weight discrepancies (T2). CONCLUSION The negative thoughts and the actual (both subjectively reported and objectively measured)-ideal weight discrepancies constitute a vicious cycle, related to higher ED symptoms. Prevention of eating disorders should be directed to adolescents who manifest large weight discrepancies or high levels of negative thoughts about eating, as they are at risk for developing eating disorder symptoms.