Very few people look good thin as a rail and it's certainly not healthy for most, though there are a few who are naturally thin due to genetics, culture, metabolism, or whatever, and it's really their business. I'd prefer someone a little overweight to someone thin as an haute couture model any day.
Then you make up the majority cause this has been studied. Most men prefer a woman with some meat on her rather than a skinny woman. It seems men might like to fool around with skinny women but they rarely seem to want to be with one or marry a skinny woman.