Common among dancers: Anorexia and general eating disorders

I would definitely keep watch over the situation. At 11 years old, we don't have the maturity to understand what these choices mean for us. Her body will change and evolve with puberty and you don't want her to try harder and harder to avoid it. 

There are a few things to think about in this type of situation. First, she is exercising multiple hours a day with not very many calories. Her body could potentially be starving which can cause problems with muscles and internal organs. We need nutrition to grow healthy and she may not be getting what her body needs to function and grow properly.

Second, anorexia and general eating disorders is common among dancers. You can't tell yet how she will process or internalize the messages she is getting about being slim. You definitely don't want her to acquire an eating disorder and we usually can't tell it's happening until it's already happened. 

Another thing to think about is her identity. If she identifies with being slim, she could have problems in the future when her body does change or when she is no longer a dancer. Will she be able to go back to normal eating at some point in time or is she creating habits that will be difficult to break later? Will she be accepting if her body gains weight as she develops? It's hard to answer these questions with such a young girl since there isn't much life experience to use as information.

I would also take a look at how rigid she is being. Extremes aren't useful in too many areas in life, whereas the grey area and being flexible take us a long way. Is she able to be flexible, in general, or is she more rigid? People with eating disorders tend to be very rigid (black and white thinking).

I would also applaud her determination and her strength. Those are great qualities that will help her through life. I would praise her for her strengths and watch out for her attitudes on eating and her body. 

The bottom line is trust your intuition. You know her better than anybody. Good luck to you and your daughter.