Gravity has significant implications for our bodies and the way we live. We have evolved with gravity and our body grows and decays according to it. Gravity is the reason we walk on this planet. A comparison of living on a gravity-based planet (such as Earth) and weightless environment can provide more detail for this question.
If we spend too long in space, we will start to have bone issues. The astronauts who spend a long time in space usually exhibit weaker bones due to non-use (when we can fly around in the space shuttle, why would we walk? and that weakens the leg bones from non-use).
On the other hand, gravity pulls us down all the time. This means that we lose part of our height every day and over a lifetime, we may lose as much as couple of inches of our height (something not observed in space). Our spine bends over time due to the gravity of the planet and we get slightly larger waists over time due to the compression caused by gravity.
There are a number of other effects of gravity on us and our bodies. But needless to say, it strongly affects how we live (think how nice it would be to fly instead of walking on Earth).
Hope this helps.