Regarding 'grossly overweight' - every fat person knows s/he is fat. You're not telling them anything they don't know. And you're not going to give them an incentive to lose weight by doing so.
Seriously, the idea that I could have just not realised I'm fat baffles me.
Clip from white chicks about that (opposite of a fat person thinking they are not, but similar principal I guess): http://www.youtube.com/watch?v=6Gy4xMgArmk (dressing room scene -- possibly NSFW)