Thank you for your question regarding whether, if you lose weight and build muscle whether your arm skin will retract or sag after a brachioplasty. This is a generalized question. Therefore the answer will be generalized also. It is conceivable that if you lose enough weight, the arm skin will sag. However, it's equally conceivable that if you build enough muscle, the skin will not sag. Therefore, I suggest you always try to lose as much weight as possible and build up as much muscle as possible. This will lead to the best situation. Therefore, the skin should tighten. If the skin is loose, I would suggest losing weight and building muscle to have the skin snap back. I hope this helps to answer your question regarding whether, if you lose weight and build muscle whether your arm skin will retract or sag after a brachioplasty. I specialize in arm lifts. I hope that I have answered your questions regarding the arm reduction. If you have any more questions regarding the arm lift, arm reduction, brachioplasty or arm crease fat grafting, please contact my office. Since a brachioplasty or arm lift surgery is a difficult procedure, please seek an experienced, board certified plastic surgeon with significant experience performing these types of arm lifts. Do your research. Make sure your chosen plastic surgeon has performed at least 100 arm lifts. Make sure they have the before and after pictures to prove it. Carefully examine their before and after pictures and check their reviews on RealSelf. Sincerely, Dr. Katzen. (“Verified” Plastic Surgeon, President of the American Society of Bariatric Plastic Surgeons, certified by the American Board of Plastic Surgery, Fellow of the International Society of Aesthetic Plastic Surgery, American College of Surgery, International College of Surgery, and American Board of Metabolic and Bariatric Surgery, and member of the American Society of Plastic Surgery, American Academy of Cosmetic Surgery and RealSelf Hall of Fame.)