Also the best way to let her know is when you're out with her make it a point to leave your eyes on all the thinner, more attractive girls in your vicinity. If this doesn't inspire her to get with the program then she's not worth it anyway.
And everything said there is assuming you're doing your part to stay in shape, too.
--
http://img.photobucket.com/albums/v712/ExTha/10and14.jpg
'I am the master of your whole keep. I am the pastor, flock ya like sheep.'