Well I will chime in here and agree with the walking. I started at 298 and it WAS hard, yes it was!!
I had to stop and rest, lean on poles, sit on rocks, etc., every few minutes. But you CAN do it! Just do what you can and don't feel as if you should be doing mega workouts. You will be amazed at how quickly you can start doing more bit by bit. Go for it!!!!