Study finds that a lifetime of regular exercise slows down aging.
I suggest that, if you are young you create two savings accounts. One for your retirement and the second an exercise savings account so that you have the health to enjoy the money that you saved for retirement.
For the first account talk to a financial planner or just start saving whatever you can afford. For the exercise account, start with walking and then add some basic strength training.
The good news is that for the exercise account, you do not need to commit to an athletic type of training schedule. You just need to have a regular schedule for moderate physical activity.