Recall the story of Milo of Croton, who carried a calf into town everyday. When by the time the calf grew into a bull, Milo's strength had increased to match the bull's weight. In other words, load bearing exercises have been taught for a long time.
But what are the real benefits apart from being able to lift heavier objects?
One study from the Journal of Bone and Mineral Research, found here, shows that load bearing exercise before the years of puberty can help to increase bone density, and that such increase is retained in later years so as to reduce the possibility of bone fractures in the elder years.
A second, non-government funded research study, found here, shows the possibility of increasing bone density into adulthood from continued load bearing exercise.
This is not to imply that a calcium and vitamin D rich diet does not help build healthy bones, but rather that in today's busy world of fast food, and sometimes poor eating habits, one can still find the time to do a little exercise today; especially if that exercise can prevent bone fractures in the future.
Since the above studies suggest that lifting weights can increase bone density in the areas specific to that exercise, it seems possible to single out the specific exercise you enjoy personally. For instance, there probably is little need for bench press. Since most bone fractures in the elderly appear around the hips, back, and legs, you might focus on squats or lunges with only minimal weight.
The goal in any routine exercise-for the average person and not the competing athlete-should be to find something healthy, time effective, and most of all, fun. Of course it is imperative to consult your physician before attempting any new exercises.