There has been some buzz among fashionistas about Michelle Obama's recent sleeveless stylings. I've seen pieces about this on the Today Show last week and Good Morning America this morning. Both features made an issue of her work-out regime contributing to her toned arms. There is even a blog post on the subject.
All this reminds me of an important exercise principle I learned some time ago: Fat doesn't belong to the muscles around it. You can't lose belly fat by doing sit-ups or lose arm fat by doing arm exercises. You have to lose fat overall to lose fat in any particular spot on your body. Fat comes off sort of in reverse order of how it went on. Arm exercises are good, but they won't cause arm fat to go away.