I think it's great that so much discussion has come out of this blog. I am a product of a competitive high school program that didn't have an eating disorder problem... and a fairly mediocre DIII women's program where EDs ran rampant. These are some of my random thoughts on the subject.
Where I went to high school, weight was brought up from time to time - usually indirectly, but directly once. I once heard my HS coach say to his assistant that a teammate of mine would run well this year as long as she kept her weight down. When I was talking about an injury I was struggling with during my sophomore year of college, my HS coach commented, positively, that I didn't look like I had gained any weight. The best runner on my team was 5'4 and 135 lbs, and she publicly lost 10 lbs (after our coach told her dad that she'd be a better runner if she lost the weight; she had a large frame and carried a lot of muscle) the summer before her senior year in the hopes that she would break out and be rid of her plantar fasciitis. She lowered our school record from 18:55 to 18:35, earned all-state accolades, and successfully kept her PF at bay. To this day, she does not have an ED or lingering food issues.
I went from being the 8th best girl on the 8th best team in the state to being the 5th scorer on a team that only finished in the top half of our NCAA regional my freshman year. Academically, my school was very prestigious, and my teammates were all very high achievers in the classroom. We were definitely a group of perfectionists. Eating disorders were very prevalent my freshman and senior years. It went ignored by my coach (he just wanted the problem to go away). I watched healthy freshmen look up to an emaciated senior and begin to adopt her eating habits.
One of the things I think that drives EDs on women's team is the perception that thinner=faster. During preseason, it's not always certain who will be the fastest runners on the team. So the women look at the thinnest girl on the team and start to adopt her eating habits. When the thinnest girl on your team only eats raw fruits and vegetables and tea, it's pretty obvious when people begin to copy her.... But my emaciated teammate never ran well, and then we just had a rampant ED epidemic making everyone go a little crazy. It didn't matter how many times we had sessions with the athletic trainer or the school nutritionist, once things take hold, they're really hard to eliminate.
I think it is usually inappropriate for a coach to make a comment about an athlete's weight, ESPECIALLY when it is a male coach and a female athlete. I think it can be handled delicately and successfully, but it takes special care to do that. You have to remember that young women are generally very eager to please and will assume that if losing 10 lbs is good, 15 might be better. When a woman loses weight and PRs, it seems logical to lose more weight in order to set more PRs. And it works... until she starts getting stress fractures and anemia.