I'm going to have to disagree and I don't do it often...........it's PROVEN that at that high of intensity, glucose is the first to be burned........then we are talking anytrhing you've eaten, carbs, protein, muscle then fat......it's not until the later stages (35-45minutes) that you truly tap into your fat stores........at a lower intensity, fat stores are tapped in first......I walk on the treadmill at its highest elevation at a decent speed and have dropped an incredible amount of fat...............