One case = anecdote. There is actually some evidence that you can't counteract the effects of sitting with exercise, unless you exercise more than you sit. And what exactly does "I'm healthy" mean? Is that what the doctor says after doing some test or is it just how you feel? What would be the status of your health (as measured by tests from a doctor) if you had an active job and some moderate exercise for the same period of 13 years?
source: http://m.runnersworld.com/health/sitting-is-the-new-smoking-...