When you go to the space you live in the zero-G situations. The astronauts in orbit feel apparent weightlessness not because there is no gravity but because they move with the same acceleration as the spacecraft.
You feel weight if there is gravity and something pushes you against the force of gravity (your weight). In the orbit there is gravity (comparatively less than on the surface) but as the spacecraft is continuously falling (accelerating) due to centripetal force, there is nothing that pushes you. You are in a situation of continuous falling!
You do not need to go to space to feel zero-G. The zero-G aircraft also provides zero-G experience on Earth. You may have experienced free fall not completely but a little bit in elevators.
When astronauts stay in space for longer periods of time, their spines stretch causing them to become taller than on Earth. The spines can stretch up to 3 inches and starts to shrink again when they come back to Earth. So do not feel exited if your height is less.
Not just the height but there are other side effects to human body in the space. It is almost no load to the body no gravity causes the heat to become smaller. The heart needs less work to do to pump blood to other areas of the body and blood flows in upper part of the body than in lower parts (since heart pumps blood to the move blood to the upper region).
The human body is adapted to live in the Earth not in space. So, going to zero-G is completely a different situation of human body. Staying in space for prolonged periods of time can case may side effects. The muscles and bones begin to weaken. The inner ear is also affected by gravity and the face is also swollen. The human body will have side effects in the microgravity situations as it will be a completely different situation for the body to adapt.
