The short answer: he doesn't.
There's this guy at work that has had a spare tire ever since I've known him. Well, it's actually more like a Tractor Tire (one of those big tractors that moves large hills). The guy had the worse eating habits I've seen in a long time (habits that I didn't even come close to in H.S. or college), everything he ate was either deep fried or can sit on a shelf for about 40 years and still be preserved inside a ship wreck. But in the last few months he's been snacking on nothing but fruit, nuts (sticks, rocks, leaves...) and salads. I have to admit, that takes some discipline and it's working.
So this morning some women at work were all standing out in the hall talking about how impressive it is that he's done this, they then followed it up with compliments to him and then they asked me if I've noticed. My short answer was "yeah" but keeping within the "guy code of honor", I was following the centuries old tradition by not saying anything about it. Seriously, there's nothing more strange than two guys sitting around talking about how big their butts and thighs look. It just doesn't happen. When guys compliment each other it's more like "Hey Dude, I bet you can outrun a bull if it were chasing you after you took its Pork Grinds" or something like that. In guy language that means "Hey, you've lost weight, so now the Hooters waitresses will probably refill your drink without asking".