HomeHealthArchivesFeb 2005


To Burn Fat, How Fast?

Who burns more fat, the tortoise or the hare?

Runner's World calls it a tie. The "slow-and-steady" camp advises working out at a less-than-taxing pace of about 65 percent to 73 percent of your maximum heart rate (220 minus your age, measured over a minute). The thinking is that within that "fat-burning zone," the body gets about half its fuel from fat. Work your heart harder, say at about 85 percent of maximum, and your body will rely more on carbohydrates. Only about a third of the calories you'll burn will come from fat.

The other side, though, points out that when you work harder, you burn more calories. Though your body may not burn as much fat in percentage terms, the amount of fat burned in absolute terms increases right along with the increase in calories burned.

An example: If you work out for half an hour at 65 percent of maximum heart rate, burning 220 calories, then 50 percent of those calories come from fat, for a total of 110 fat calories burned.

If, on the other hand, you step up to 85 percent of your maximum heart rate for half an hour, you'll burn 330 calories. True, only about 33 percent of the calories will come from fat, but 33 percent of 330 is 110 fat calories burned-the same as in the slower workout, but with a higher number of calories burned overall.

Another way to increase total calories burned, of course, is to work out for a longer period-which is easier the slower you go.