Really wish they had the budget to pull off how deformed (from our perspective on Earth) Belters appear in the books. Astronauts have to do physical therapy after coming back from space, imagine living your life out there.
The first belter shown has clearly different proportions compared to Earth humans. Easier to do because that one was restrained and wasn't a main character. But they are aware of that.
> imagine living your life out there.
Worse than that, imagine multiple generations out there. We don't know what's the effect of zero-g on bone growth is.