He says most people are able to change their bodies. Building muscle increases metabolism and you are never too old to do it, Karas says. Someone who adds five pounds of muscle can burn an additional 250 calories a day. If they keep that muscle on for one year, they will burn a total of 91,250 extra calories. This is nonsense, says Karas.
Few people have radically slow metabolisms, a rare medical condition.
While everyone's metabolism varies, the difference is largely a factor of how much lean-muscle mass we carry. And the only way you'll start to build that muscle is by embracing strength and resistance training says Karas. Fitness Expert Jim Karas. Fitness Expert Jim Karas. ABC News Internet Ventures.