What is the best treatment for upper arms that are saggy ?
There is a very effective surgical option for sagging excess arm skin. It is called a brachioplasty or arm lift. The excess skin and underlying fat (if any exists) are removed. The final scar line is usually a fine line that can be hidden on the back of the arm where it will not be noticed in sleeveless clothing. You’re right that treatments like creams and skin tightening procedures are usually ineffective for such a problem; they simply cannot adequately tighten he excess skin to any appreciable extent. See the link below for some examples of brachioplasty.
Triple Board Certified Plastic Surgeon