In a way. It reduces appetite, which reduces urge to eat lots of junk. But it doesn't stop people from eating junk, they just eat a little bit of junk instead of a lot of it.

The end goal should be to make it easier to eat healthy foods over junk in the first place, but that's a long way off. If we're talking the most direct way to address obesity as an epidemic, namely reducing the adverse health effects it has across a large population, the meds are the most immediate and impactful short term solution.