Spending hours on the elliptical, for example, keeps levels of the stress-hormone cortisol elevated, and boosts fat storage. So, try interval training…That’s short bursts of intense exercise, followed by quick cool-downs. Like, running flat-out for 30 seconds, then jogging for two minutes to recover. Research at the University of Western Australia found that 15 to 20 minutes of intervals burned enough calories to help overweight dieters lose a‑pound a week…While 40 minutes of steady exercise resulted in NO weight loss.