In art sports or with great weight involvement (horse riding, motorcycling) training style chosen by the trainer will influence the self-concept that the athlete has.
There is a meta-analysis from Smolak et al. (2010) in the International Journal Of Eating Disorders (27:4, pages 371-380) titled "Female athletes and eating problems: A meta-analysis". It might be helpful...
In a very well controlled prospective study, critical comments from a teacher or coach was one of the most potent risk factors for developing ED in a sample with high weight and shape concerns. Jacobi C, Fittig E, Bryson SW, Wilfley D, Kraemer HC, Taylor CB. (2011) Who is really at risk? Identifying risk factors for subthreshold and full syndrome eating disorders in a high-risk sample. Psychological Medicine. 2011 Sep;41(9):1939-49.
I think there is a lot of research to be done in this field. Coaching practices (style of coaching, similar to parenting style), and also the relationships between coaches and their athletes are crucial in determining the young athletes behaviors. Here's an interesting study about the athletes' perceptions about their coaches influences:
Kerr, Bermon, & De Souza
JOURNAL OF APPLIED SPORT PSYCHOLOGY, 18: 28–43, 2006
I think it is certain that the coach has a profound influence on the athlete, Whether it is positive or negative depends on the coach and His/her approach to life.