Probably, says Seattle osteoporosis researcher Barbara Drinkwater, Ph.D., "You build bone by always asking it to do a little bit more than it's used to," she says. "People who go backpacking are asking their bones to do this extra work."
Now for the bad news: "It's easier to lose bone mass than to build it," says Dr. Drinkwater. "By the time you're 18 or 19, you have most of the bone you're going to have." Chances are, you had plenty back in those days, but if you rest on your laurels, your bones will slowly wither away. Cheer up, though: Backpacking can slow this loss.
Guys, if you think a Y chromosome makes you immune from osteoporosis worries, think again. "Men do need to worry about osteoporosis because now that they're living longer, they're living to the ages where they can get osteoporitic fractures," says Dr. Drinkwater.