What can be done against excessively thin body image in the media?

Don't buy their good. One of the major reasons for media's existence, besides transmission of news & information, is as a sales medium. In order to sell something, you use "attractive" images, not necessarily realistic or healthy ones. If you don't like the use of thin body images, use the power of your pocket book and hit them where it hurts. Don't buy their goods & services. And write letters to the editor.