An arm lift is a cosmetic surgical procedure to improve the appearance of the under portion of your upper arms.During an arm lift — also known as brachioplasty — excess skin and fat are removed from between the armpit and elbow. The remaining skin is placed back over the newly repositioned contours to create a more toned look.it’s done when you get older, the skin on your upper arms changes — sagging and becoming loose. Significant weight loss also can cause the undersides of your upper arms to droop.While exercise can strengthen and improve muscle tone in the upper arm, it can’t address excess skin that has lost elasticity.You might choose to have an arm lift if the undersides of your upper arms are sagging. An arm lift might also boost your body image.