I would suggest an eliptical machine over a treadmill...it's more of a full body workout, with little to no impact on the knees. Also, don't necessarily cut meat out, but make sure its LEAN meat (chicken breast, turkey, lean steak, salmon, etc...). For me, I'm always eating steak as much as I can, but its always very lean (sirloin is a good cut). Nutirition is above all the most important aspect of any workout program...your body simply cannot build muscle or burn fat without the right kind of fuel.