The fat buffers it. When I was a mini moon (5'7" 195 lbs) I never had problems with chafing, even if I ran for 6 hours straight (which I did, I run marathons, which is at least in part why I'm no longer as fat). Now that I'm a reasonable size (150 lbs) I feel everything more. I basically have permanent chafe marks from my sports bra. Soooo attractive :(