Just kill off those nasty fat cells that you have been over-feeding: Obese Monkeys Lose Weight On Drug That Attacks Blood Supply of Fat Cells.
Assuming this will be somewhat safer than bariatric surgery, we'll all be able to eat all we want and as inactive as we want, and we'll all be as skinny as models. Being in shape will lose all of its virtue because it will be effortless.
Maybe being fat will then come into fashion.