http://www.cnn.com/2011/HEALTH/03/01/overweight.doctors.health/index.html?hpt=C2
If you're female, doctors don't hesitate to tell you you're overweight even when you aren't. If you're female and weigh more than 90 pounds, regardless of your height, you will be told you are fat by at least one doctor in your life.
If you're male, you may never have the word "fat" applied to you, even when you have floppy man-boobs and should be wearing a size 48D bra to control them, and a belly that overhangs your belt enough to be considered an "apron". You might hear "overweight", but not "fat".