Lots of disagreement about this one, and lots of evidence to argue either side. Here we go: the Boston Globe reports on research conducted at the University of
Birmingham that assigned seven people to cycle three days a
week, followed by an intense session an hour later without eating.
Another seven people followed the same regime, without the instruction
to fast. Though members of
the group that didn’t eat performed worse on the intensive training,
they burned a higher proportion of fat to carbohydrates than the group
that ate.
The Globe judiciously reports that many health experts argue that even though people may burn more fat this way, it is mostly
fat within the muscles that will be lost and won’t make a big difference
to people trying to lose weight. The paper quotes Andrew Greenberg,
director of the Obesity and Metabolism Laboratory at Tufts University, warning: “When you exercise [without eating],
fat is broken down more quickly in the muscle. You may enhance how you burn the fat in
the muscles, but it doesn’t affect your overall body fat.’’