The answer, of course, lies in the
principle of special relativity.
According to Einstein, we are all constantly moving
at the speed of light through the four dimensions of
spacetime.
Now, as you and I are sitting on our
respective asses scarfing potato chips and staring
at the phosphorescent glow, we are not moving
relative to each other. Our relative stasis means
that the entirety of our spacetime vectors are
directed into the time dimension. Maybe that
sensation you feel isn't your bum falling asleep,
but the rush from your lightspeed plunge through time.
A person who is jogging, however, is in motion through
space. In other words, she has a space component as
well as a time component in her spacetime vector.
Since a portion of her lightspeed motion through
spacetime is diverted towards her movement in space, she
is moving more slowly through time than us fatasses.
It follows that, because our greasy crumb-covered bodies
are moving more quickly through time, we will age at a
faster rate.
Thus people who jog on a regular basis actually
experience less time than us lazy stationary cake
eaters, and on average will live longer relative to us.
QED.