Sheesh! I have
seen this phrase misused a few times now (even in
Roger Mellie's Profanisaurus!). Let me clear things up:
Saddlebags is a word to describe the bulging areas of fat on the upper outer thighs of ladies, in a way that resembles saddle
bags being carries on a horse.
The expression was used in Ace Ventura: Pet Detective. I can't remember exactly how though. It was
something along the lines of:
Melissa
Robinson claims she isn't fat. Ace says
something along the lines of "yeh, whatever you say, saddlebags!"