High-level Athletes' Motivation for Sport and Susceptibility to Doping: The Mediating 2 Role of Eating Behaviours 3 Introduction 4 The World Anti-Doping Agency Code (2015) defines doping as a violation of one or more 5 anti-doping rules as set forth in Article 2.1 through Article 2.8. Petróczi (2007) defined 6 doping as the use of prohibited means to enhance performance with the intention of gaining a 7 competitive advantage over the opponent. As doping behaviours are difficult to capture 8 directly, most studies have focused on attitudes towards doping (e.g., Petróczi & Aidman, 9 2009) and the motivation or intention to do so, taking into account variables such as 10 susceptibility to doping and social appraisal (e.g., Barkoukis, Lazuras, Tsorbatzoudis, & 11 Rodafinos, 2013). Self-determination theory (SDT) has been applied for the prediction of a 12 number of health-related behaviours (e.g., Hagger et al., 2014), including doping (see Chan et 13 al., 2018b, for a review) and eating behaviours (Hagger, Chatzisarantis, & Harris, 2006). 14 However, no research to date has examined these processes together to determine whether 15 and how motivation, eating behaviours, and susceptibility to doping are related. The purpose 16 of the present study was therefore to gain deeper insight into the relationship between 17 motivation for sport and the susceptibility to doping within the SDT framework through the 18 potential mediating role of eating behaviour in this relationship. A deeper understanding of 19 the psychological processes that underlie doping will better equip coaches and other frontline 20 personnel to identify maladaptive behaviours. 21 Sport motivation and susceptibility to doping 22 According to SDT, there are two broad types of motivation: autonomous motivation 23 and controlled motivation (Ryan & Deci, 2000, 2008). Autonomous motivation occurs when 24 an individual feels independently and freely engaged in a behaviour. It has been shown to 25 predict intended and actual effort (Deci & Ryan, 1991) and includes intrinsic motivation and