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Article History

Received: 4 May 2018

Accepted: 14 August 2019

First Online: 29 August 2019

Ethics approval and consent to participate

: Ethics approval was obtained from the College of Medicine, Biological Sciences and Psychology ethics representative at the University of Leicester. School principals provided written consent for their school to participate. Parents/guardians were provided with an opt out consent form and only pupils who did not return the opt out consent form participated. Participants provided assent prior to each data collection session and could withdraw at any time.

: Not applicable.

: All authors have completed the Unified Competing Interest form (available on request from the corresponding author) and declare: no support from any organisation for the submitted work, no financial relationships with any organisations that might have an interest in the submitted work in the previous three years and no competing interest related to this work. MJD and KK reports personal fees from Novo Nordisk, Sanofi-Aventis, Lilly, Merck Sharp & Dohme, Boehringer Ingelheim, AstraZeneca, Janssen, Servier, Mitsubishi Tanabe Pharma Corporation, Takeda Pharmaceuticals International Inc. and grants from Novo Nordisk, Sanofi-Aventis, Lilly, Boehringer Ingelheim, and Janssen. Outside of the submitted work, JC reports grants from Public Health Wales. CLE reports grants from National Institute for Health Research Public Health Research during the conduct of the study and is an Associate Editor for BMC Public Health. RTE, DB, TG, DMH, LS and TY all have nothing to declare.