Participants were recruited by using a convenience sampling method. Potential participants were reached through lecturers and professors who are teaching classes at different universities in Istanbul, Turkey.

Participants were asked to fill out a questionnaire package covering Demographic Information Form, Eating Disorders Examination Questionnaire (EDEQ), Eating Attitudes Test - 40 (EAT-40), Body Image Satisfaction Questionnaire (BISQ), and Sociocultural Attitudes towards Appearance Questionnaire-4-Revised (SATAQ-4R). Filling out the questionnaire package took approximately 25-minutes.

Participants were randomly assigned to one of these conditions:

Experimental condition: Healthy Eating Attitudes and Behaviours Group Program - 6 weekly sessions, each session was about 45-minutes to 60-minutes

Active control condition: Eating Disorders and Body Dissatisfaction: A Group Work - single session about 1.5 hours to 2 hours

Wait-list control condition: Participants in this condition were informed that they will be asked to fill out questionnaires that sent to them, and at the end of 6 months, they will be invited to participate in Healthy Eating Attitudes and Behaviours Group Program.

The program has been developed by Clinical Psychologist Başak İnce and Psychiatrist Prof. Dr Başak Yücel. The session topics and contents of this program were based on the Fairburn (2008)'s book titled Cognitive- Behavior Treatment and Eating Disorders and 10-week online version of StudentBodies program designed by Saekow and her colleagues (2015). Program protocol was written based on Fairburn (2008)'s book titled Cognitive- Behavior Treatment and Eating Disorders and Fursland and her colleagues (2007)'s book titled Overcoming Disordered Eating.

This program aimed to inform participants about the causes and consequences of eating disorders, teach cognitive and behavioural techniques to change their unhealthy eating attitudes and behaviours, and provide support during their attitudinal and behavioural changes. Each week, participants were asked to complete homework activities which were related to topics covered in each session.

This questionnaire was used for measuring restraint eating, shape concern, weight concern, eating concern and general eating disorders related psychopathology. There are four subscales named Restraint, Eating Concern, Shape Concern and Weight Concern, and a total score. The minimum score for this scale is 0, while the maximum score is 6. Higher scores indicate greater levels of disordered eating attitudes and behaviours. This questionnaire was used to assess the level of change from baseline to post-treatment and from baseline to 1 month follow up.

This questionnaire was used for measuring preoccupation with body weight and shape. Scores can range from 34 (minimum) to 204 (maximum). Higher scores indicate greater levels of body dissatisfaction. This questionnaire was used to assess the level of change from baseline to post-treatment and from baseline to 1 month follow up.

This questionnaire was used for measuring different aspects of emotion regulation difficulties. The minimum score for this scale is 0, while the maximum score is 64. Higher scores indicate greater levels of difficulty in emotion regulation. This questionnaire was used to assess the level of change from baseline to post-treatment and from baseline to 1 month follow up.

This questionnaire was used to measure disordered eating attitudes and behaviours. Score of 30 and greater indicates greater disordered eating attitudes.