Some people simply have a higher metabolic speed than others. They burn more calories at rest, as well as during activities. I know a few people who can eat like a horse and don't get fat, and their activity level doesn't seem higher than average. I'm not sure if exercise increases metabolism, it's most likely a chemical thing.

__________________
1985 380SE Blue/Blue - 230,000 miles
2012 Subaru Forester 5-speed
2005 Toyota Sienna
2004 Chrysler Sebring convertible
1999 Toyota Tacoma