As is the case with many lifestyle changes, fully committing to an ongoing exercise program is not something most people do instantly. Rather, most people tend to go through a series of engagement stages during which they learn about and evaluate how exercise will affect them. These engagement stages tend to go something like this:

Challenge. Inactive people usually begin to exercise as a result of being challenged by a moment of realization of how out of shape they have become. That moment might occur when someone finds themselves winded after climbing a flight of stairs or moving furniture, or when they realize they have gained back all the weight they lost. It is very common to become challenged by reading about the health risks of a inactive life (as you are doing now). In the challenge stage a person moves from not thinking about exercise to considering making a change. They may not know how it all works, but they become willing to give it a try.