Also, if you want to get all geeky, the math argues against the fat-burning zone. Walk two miles in an hour, and you’ll burn about 200 calories, with roughly 140 of them fueled by fat. Cycle moderately for that time, and you’ll burn about 500 calories, with about 250 of them fueled by fat — so you’ll burn more calories and more fat. “When I worked with people in a gym, I would tell them, ‘Ultimately, it’s a matter of calories; the fat burn will take care of itself,’ ” Breen says.
But what about this fundamental critique? There's some truth to this, isn't there?
I don't claim expertise on the method or the intent but what I have read of the Maffetone method is more centered on improved performance than optimal amount of fat burning (vs. optimal percentage of fat burning while still getting a training effect). His claims are by to my understanding, again limited, are the body trains itself to be more efficient at breaking fat down to train so one doesn't hit a wall during endurance events due to glycogen depletion.
While I have had good results from the method, I have not realized a training effect where it requires great physical to get the heart rate into or above the specified zone (180 - age minus correction factors). I have had the effect that I can move faster without exceeding the zone but it's still easy for me to exceed it.