Self reported height and weight information was converted to body mass index (BMI) values, which were age= and gender-adjusted into BMI z scores (Child Growth Foundation,1996). At T1, the BMI z score mean for boys was 0.38 (SD = 1.51) and for girls it was 0.10 (SD = 1.25). At T2,boys' mean BMI z score mean was 0.27 (SD = 1.37) and was 0.04 (SD = 1.06) for girls. Following institutional ethical approval, five schools across the United kingdom were sent questionnaire packs (including consent forms and parent letters). Which were given to all pupils aged within the required age range of the study (12-14 years old at T1). Questionnaires were completed during a regular timetable class period. All returned questionnaires were assigned a specific identification code in order for them to be matched to the longitudinal follow-up. A follow-up assessment was conducted approximately 12-months later (T2). using the same procedure as at T1.