However, with girls, I deal with this crap more often than I would not. We had to sort of do an intervention for one of the girls in the collegiate club. Something like trying to train on 500-700 calories a day. I get pre-teen and teen girls suffering from anemia or lack of energy way more rampant than I'd prefer (which to be honest is what 1 out of every 15-25 girls, maybe 1/50 or 1/100).
Right, although at that point we've crossed the line into the instances where the child actually IS starving themselves due to a physical/psychological problem. It's not the same as being picky or even engaging in a power struggle over food the way a toddler might commonly do. The only response in my opinion is monitoring and professional help. Honestly I think in some instances monitoring and early detection with ongoing treatment through adolescence and early adulthood is all you can do. There is some perfect storm of personality factors and experiences that just makes certain things likely, and monitoring and treatment is important. No one should ever think that their child is immune because of x factor (we go to a "nice" gym, etc). Environment plays a role but in my experience personality is a dominant factor.
Any gymnastics is already a body conscious environment and that's a strike there already no matter how careful you are. I'm just being honest, especially since there seems to be this insane current thought that the incidence of eating disorders is "low" in gymnastics. I never felt I was in a gymnastics environment where weight loss was stressed, or where there was weighing, etc, and I still know girls who were hospitalized with eating disorders. Now the incidence of severe eating disorders must be fairly low, but just disordered eating to an extent that COULD be dangerous. I don't know what the official party line is right now, but my own experience and that has to be upwards of 80% of high level gymnasts. And I feel it's mostly a personality and control thing.
That said these kinds of comments don't help create a positive body image and they can trigger these kinds of behaviors (if not a full blown eating disorder). Also, disordered eating is going to be a given in an environment where there's weighing and weight goals, which is unhealthy and disturbing - it could lead to a great deal of health problems. My point is, though, even without blatant comments there are many subtle indicators that can drive these behaviors with personalities that are so inclined. To use my earlier points, food as a form of control within a family dynamic is not an uncommon way for disordered eating to start. Ultimately they WILL control how much they eat, unless you plan to resort to abusive tactics. So, forcing and consequences has a fair amount of room to backfire.
Again, I think the most straightforward way to deal with this in younger kids (before there is a problem) is that the parent provides a wide variety of different foods at regular meals and snack times, and the child decides how much to eat. This is not only the approach recommended by many nutrionists and pediatric therapists now, but it just makes sense in order to allow the child a healthy relationship with food where they don't feel the need to battle for control. They will learn that familiar things they will eat will be regularly available (and btw the renowned nutritionist I linked to recommends offering "less nutritious" foods regularly to avoid the concept of "forbidden" foods - barring intolerances or allergies, obviously) and they can choose to eat to their hunger level.
Extreme picky eating in young children is sometimes diagnosed as Eating Disorder NOS (not otherwise specified) and that is another story, often related to sensory issues and not through the fault of the parent's feeding. In this case you need different approaches and even therapy to address a feeding disorder. Some dislike of textures or strong flavors is to be expected from children in my opinion (also not the fault of the parents) and doesn't make sense to me to be extremely concerned if they'll eat some things from each group.