I share your disdain for fat-shaming but your understanding of metabolic science is simply incorrect.

There is no mechanism for the body to discard chemical energy that it has absorbed into the bloodstream except to store it as fat. There are no hormones or genes affecting the rate that absorbed nutrients are stored as fat, because there is no other metabolic pathway for those nutrients to take.

There will never be a drug which regulates fat storage, because that would involve messing with your body's ability to lower its blood glucose levels and kill you by hyperglycemia. Something affecting nutrient absorption might be possible but I don't know.

Body fat is not simply a matter of calories eaten vs calories burnt.

There are several ways your body burns energy (not just exercise), but otherwise it really is that simple. But that's not to minimize the difficulty that people have maintaining their weight.

There are genetic, hormonal, health, and environmental factors which affect things like hunger, cravings, and satiety. The reason that people have a hard time keeping large amounts of weight off, aside from the inherent difficulty of significant lifestyle changes, is that their bodies are placed into an altered hormonal state for many months or even years as a result of their weight loss, which includes elevated levels of appetite hormones like leptin.