"Offroad cycling can increase it a lot, with out the unwanted effects of jogging (Impact injuries to your joints) cycleing 5-10 miles every day will help a lot, just make sure its closer to 10 miles then 5 miles. 5 Miles is not much, and make sure the intensity is high, ie pedal hard!"
How does offroad cyclying increase bone density? The whole reason running increases bone density is because it is high impact. Is off-road cycling really high impact. I'm seriously asking as I on't know anything about it.
Francisco, you're missing what I'm saying. I agree with you that cycling burns a lot of calories. But what I'm saying is that once you stop cycling you stop burning (excess) calories in a short period of time. The reason probably (they are not sure exactly why but have theories) being that you don't cross your anareobic threshhold. One theory is that the amount of damage you do to your muscles when you lift requires an increased expenditure of energy to repair the damage.
This is why doing sprints or intense rides may boost your metabolism longer. Interval training in any aerobic activity will do this precisely because it does become anaerobic repeatedly. However, you still do not acheive the muscular breakdown on the same level as weightlifting, nor do you produce any (significant?) HGH.
BTW, last year training for the Malibu and Superfrog triathalons I was biking 100+ miles per week. So it's not like I'm against biking.