Right now people only stay on the ISS for 6 months at a time. The issue with being in a lower gravity environment is degeneration of the eyes, skeletal structure, etc.

If someone were to travel to Mars they would need exercise machines they can use on the way there, back and on the planet like they do on the ISS. I think the unfortunate reality is even if they went through the effort of doing all this whoever went to mars would probably have severe macular and skeletal degeneration. If that doesn't kill them the exposure to all the radiation probably will.

Is travelling through the stars impossible?