The fat that survived your BBL after 8 years is now living fat, just like fat in the rest of your body. A weight loss injection should not specifically "kill" the transferred fat, but if you lose overall body fat, the buttock fat can shrink too. How much change you see depends on how much weight you lose, your genetics, where you tend to lose fat first, your starting body composition, and your skin elasticity. Some patients keep a nice shape but become smaller; others notice less projection, more hip dip visibility, or looser skin after significant or rapid weight loss. The best way to protect your result is to lose weight gradually, keep protein intake adequate, do glute/leg resistance training, and avoid large weight swings if possible. Work with the clinician prescribing the medication so the weight loss is medically supervised. If you reach your goal weight and feel the BBL has changed too much, wait until your weight is stable before considering touch-up fat grafting or other revision options.