The concept of losing weight is a disasterous over-simplification of the obesity problem. It is not bodyweight that's important - it is body composition that is key, which is far more complicated. It is not losing fat that is important - it is keeping it off that should be the goal. Losing bodyfat - the delta itself - is always a Bad Thing, albeit a necessary evil for anyone who is fat. Starvation, no matter how slight, takes a toll on the body. Losing weight is a cost, not a benefit, and it is certainly should never be a goal.
We should be celebrating weight loss like we celebrate cancer surgery - "Gee, sorry to hear that you had to go through it but let's hope the problem stays away. Let's have a party at your 5-year anniversary."
This is what external rotation of the shoulder looks like, with the humerus as the axis of rotation. For weightlifters who can do this it's like getting longer forearms and shoulders with more cushion for the bar. Get good at this and it will save your wrists and clavicles a lot of pain.