I think that in the past century, ballet, along with every other art form, has undergone a great deal of changes; it has evolved from its initial image.
Ballet first became widely popular in the Romantic time period, when beauty was defined in a completely different way than today. Women were considered beautiful when they looked healthy. Extreme thinness was seen as a mark of a poor lifestyle - not beauty. This mentality lasted for quite some time. Some of the most prominent ballerinas in history were quite normal in their size and shape. Look at the photographs of Anna Pavlova.... she was not skeletally thin, and yet she is considered one of the best ballerinas that has ever been. But along came George Balanchine, and introduced a whole new concept of beauty.
Balanchine wanted a change from that romantic, ultra-feminine ballerina, and that's what he achieved. His ideal dancer was six feet tall, very thin, and angular. I acknowledge that there are many body types in world, but I think I will be correct in saying that the body type favored by Balanchine was not very common naturally. Balanchine started this new mania of extreme thinness. Dancers who wanted to be successful, but did not naturally fit his mold of an ideal dancer, resorted to artificial methods of forcing their bodies to be thin.
This is the mentality that prevails today. Thousands of dancers all over the world fret and worry endlessly about their body. I think it is ridiculous to constrain ballet to people who look like walking stick insects. The ballet world needs to realize that there are others out there with a passion for ballet who do not fit the mold. This is important not only to include everybody, but also to prevent the art of ballet from becoming extinct. Any art requires a circulation of ideas, of new images. Ballet is no different. I do not think that ballet will be popular much longer if the dancers keep on getting skinnier and skinnier. It will be no longer pleasant to watch ballet; it will be disgusting.