If your surgery will keep you from doing any workouts at all, then I would lower my calorie intake some. I think you have the right idea – cut out the protein drinks for the time being. I wouldn’t worry too much about losing muscle. You’ll probably lose a little but you can always get that back – 1-3 months off shouldn’t do that much damage. You just don’t want to pack on extra pounds of body fat during that time by eating too many calories & not expending them. It’s just more work you have to do when you get back to your training. Good luck with your surgery & I hope you have a quick recovery.