Originally Posted by tandoorichicken
I disagree meeker, running is harder on the knees than simply carrying around extra weight on a daily basis. The fact is there is sound science behind recommending overweight individuals to not run, not just some blatant "fat people discrimination" on the part of the trainer. Like jerihurd said, running is extremely high impact - 25 pounds of extra weight puts 100 pounds extra load on your joints when you're just walking around, which shoots up to 250 when you run. That's a lot of wear and tear.
Biking, walking, swimming, and elliptical are all lower impact cardio activities.
But as always I say to get the most bang for your buck in the gym lift free and lift heavy (variations on squats, deadlifts, overhead pressing). It's way lower impact than any cardio activity regardless of how much weight is on the bar, and the degree to which it forces your body to adapt to stress burns waaay more fat over time than any cardio activity. Plus you build a lot of muscle, which again, helps you burn that much more fat. And in non-steroid-enhanced women (I'm assuming most if not all of you), it's dense, shapely, hawt muscle, not grotesque, veiny, boxy muscle.
Okay, weightlifting rant over.
While I agree that there are other really good, low impact workouts that are easier on the body than running and burn as many calories, I still say that if you want to run, then go for it. Start off slowly, wear good shoes, talk to your doctor and do some research on good form. I know that weightlifting works, and so I do it, but I never look forward to the weight room in the same way I look forward to a good run. I guess I would hate for someone to read this thread and use it as an excuse for not trying a workout they might really enjoy.
And as for wear and tear on the body, I think with every physical activity there is an inherent risk of injury. I totally blew out my knee on a bicycle and just last night I watched a guy throw his back out in the free weight room. Injuries happen in every sport. So do I think a person who wants to start running should avoid it because of a possible injury? No, I do not.