I find your language usage curious. "trying to coax the monkey brain into doing things you can't make it do", "the way the world is", "people can free will their way to success", "anyone with a brain chemistry imbalance or dysfunction".
You seem to imply that people have no self-control and are unable to power through difficulties. Because this is what is all about at the end of the day: self-control, one of the main things that separate us from the rest of the animal kingdom. It is the ability to regulate one's emotions, behaviors, and impulses in the face of temptations and urges.
What your parents taught you, your teachers taught you all those years during compulsory education lies on a solid foundation of self-control. Civilisation as we know is built upon it. Depends on it.
Yet your language implies that this is not the case. That humans are effectively, like toddlers, unable to use their self regulating powers to reign upon their emotions for the sake of a much better outcome in the long term. Fully unable to choose healthier foods or foods with lower calories. Fully unable to engage in free physical activities such as walking, jogging or running.
Truly makes you wonder how civilisations exist at all.
The idea that you can improve an individual's agency by having to temporarily disable a part of their brain is nonsensical. Surely, you can temporarily improve a specific decision making outcome (do I eat now?) by doing this. But you are not improving their agency anymore than you can by putting a gun on their head. In both cases, there is an external force temporarily suppressing a part of their normal decision making so they decide not to eat.
The underlying problem: lack of self-control is still there. You just tackled a symptom. There are others (deciding not to engage in physical activity for example).
A better solution would tackle the lack of self-control rather than some of the symptom. There is already some research on this area and some potential suggestions that if further investigated could help provide a better solution. But unfortunately, the solutions are virtually free and don't involve a lifetime subscription (could very well end up like diabetes medication which is arguably more critical for affected people yet with companies endlessly increasing the patents Disney style) to a drug.