The concept of fitness in the US slants more in that direction. Living in Taiwan, I knew a lot of people interested in controlling their diet but not many who were interesting in building muscle mass. Health magazines weren't full of models showing off muscles, either.

For whatever reason, there is a very American tendency to focus on muscles. Men and recently more and more women on TV are muscular. The trend has been going on for the past 50 years and the effects even show up in toys!

http://www.lhup.edu/tmitchel/wmst/pope.pdf

Edit since I can't reply: Yeah, it's a lot easier to tweet about how manly you are living off of bacon and protein powder than it is to actually hit the gym regularly.