I haven't done the 12wbt but have had my gallbladder out recently. I usually do an aerobic/strength class 2-4 times per week and I stopped completely for 3 weeks and then worked "light" and no weights for 3 more. My surgery went smoothly with no complications. So you would be limited for at least half I would think. That said, changing your eating habits and gentle exercise until you recovered would still see some effect I would think?