Ok, so no one is saying that being thin and healthy is a bad thing. But how often do people negatively comment on an overweight person's figure? How often do you think about your own body's extra flab? Fat politics is a recent field of interest, and is even taught at several U.S. universities. Fat activists are trying to convice people that any prejudice against overweight individuals need to be stopped. This means focussing on the media and beauty industry to combat the perpetuation of the idea of an ideal body. Let people be thin, let them or yourself be full figured, as long as your health isn't compromised, say by getting anorexia.
In an earlier post: Is the fat body ever invisible? I talked about Margitte Kristjansson's blog: RIOTS NOT DIETS. (Also on my 'Blogs I love' list.) She doesn't advocate that everyone should be 'fat' or overweight, but that people need to riot against the ill treatment of yourself and other people who are considered to have a less-than-ideal body. She made a little documentary on this issue:
the fat body (in)visible from Margitte Kristjansson on Vimeo.
Also check out: http://www.fatshionista.com/cms/