The "burning a higher percentage of fat" = "burning more fat overall" equivalence seems to be a pretty persistent fallacy. While it is certainly true and amply demonstrated that our bodies burn more fat (as a percentage of total calories) at a lower intensity than at a very high intensity, people don't seem to take into account the fact that you just plain burn more
calories at higher intensities. Essentially, it comes down to exercising in the most efficient manner.
For example (and I'm not trying to pick on you, locarbbarb, this is a topic that trips up tons of people):
Quote:
if someone burns 200 cal in 30 min (at the high end of their Target Heart Rate), they are burning 50% stored body fat and 50% carbs. (100 cal of stored body fat and 100 cal of stored carbs). If they take 60 min to burn 200 cal, they will use 80% fat and 20% carb, so that burns 160 cal of body fat and 40 cal. of stored carbs.
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If you spent that sixty minutes at a high intensity, you would burn 400 calories; 50 percent of that would be bodyfat, so you would burn 200 calories' worth of body fat.
In other words, you could get the same benefit of the low-intensity 60 minutes in about 45 minutes -- except not only would you have burned the same amount of fat, you would also have burned about 1.5 times the calories.
Now, in terms of effectivity, cardio interval training seems to be the best: Tremblay's 1994 study on interval training (Tremblay et al; Metabolism 43: 814-818 (1994)), showed that small amounts of interval training were greatly superior in terms of fat loss to much longer periods of low-intensity cardio — up to nine times more effective at reducing subcutaneous body fat. Cardio interval training is basically just running (or whatever) at a very high intensity for a short period of time (anywhere from ten seconds to a minute), then walking for a couple of minutes until you're pretty close to fully recovered, then running again.
Unfortunately, I don't have any information on how any of this changes with a fat-burning metabolism; I will leave that up to the other amply capable hands in this thread.