Procedure to slim down arms? (photo)

You need a formal evaluation by a licensed plastic surgeon and expert in arm lifting to determine what is best for you and your goals.
I treat problems of the upper arm in different ways depending on the nature of the problem. For those with firm, healthy, elastic upper arm skin, I use liposuction cosmetic surgery to sculpt and reduce the size of the upper arms to match the lower arm. Once the excess fat is removed, the skin shrinks to the fit the slimmer arm underneath. Liposuction of other body areas can be performed at the same time, as needed.
For patients with loose, sagging skin under their arms (or "bat wings") due to aging, gravity, or significant weight loss, liposuction will actually worsen the appearance of the arms. To properly reshape the arms, I tailor the skin to fit the underlying arm by surgically removing excess skin and fat. This procedure is called a brachioplasty (arm lift). A "mini brachioplasty" does not offer as much improvement as a full arm lift but is an option for patients with loose skin near the armpit or arm fold, leaving only a small scar in the arm crease.
Whether I perform liposuction, a full brachioplasty, or a mini arm lift, my goal is to give patients slimmer, more attractive upper arms. I suggest consulting with a board-certified plastic surgeon and expert in arm lifting. - Dr. Cohen

You should see a board certified plastic surgeon to learn what options are available to you. You may be a candidate for liposuction or non-invasive CoolSculpting to trim down your arms. Good luck.