Since January 1st I've completed 70 work-out sessions, or a total of about 7,000 minutes of cardio. And I've dropped 38 lbs.  7,000 minutes / 38lbs means I am losing a pound about every 184 minutes. That's a little more than 3 hours of cardio per pound of weight loss. I've been told this isn't sustainable. No injuries. Something's working.