With a proper vehicle, with centrifugal gravity, even an overweight and out-of-shape person could go to Mars.
If we had a propulsion system capable of sustained thrust you would not even have to endure the high-G of launch...we will get there.
It is more than just shooting a person in a tube to another planet. You need to find somebody who can be psychologically equipped to stay in that tube for 6 months without wanting to end it all by opening the hatch. You also need somebody who can keep himself occupied during the entire mission by doing hundreds of small experiments.