Hypertrophy-Specific Training : : Official Home of HST
Be careful and make sure your doctor knows what training for muscle mass entails. Consider a workout like HST since most of the time, you will be using relatively light weights.
For HST, I did squat, SLDL, bench, row, overhead press, pullups, cable crunch. Consider these
basic exercises, use suitable substitues for those you can't do right now.
For example leg extension or leg press for squats, lat pulldown for pullups...
Remember that substitutions are inferior choices, but sometimes when injured, ill, or post-op, doing something, even the less desirable choice, is better than nothing.
GBS is a pretty intense, dangerous, invasive surgery. Be very careful when starting your workout program and use light weights for a while so that you don't injure yourself, causing permanent damage.
Oh how I wish you'd came here to DF before the surgery. It possibly could have been avoided. Don't forget that dedication to diet and training is how you will keep the fat that you lose from coming back. It's a new lifestyle for a new life. Can't go back to old habits.
Good luck on your workout plan, and best wishes for a great start on building your new body.