Originally Posted by sm266
The primary source of fuel on the long slow rides are fat, you're right. However, it's rare that any "non atkins" person will burn body fat. Your body will burn the dietary fat first, I believe. Again, I'm no expert, but I've heard it comes down to calories. I could be wrong, but everything I've read for losing weight, lately, suggests intervals. I'll agree that long easy efforts have their place, and they're great calorie burners.
It is body fat that your body uses, along with glycogen, for energy. So non-low-carbers will indeed burn body fat during exercise.
One thing to remember, though, is that we're talking proportion here, not absolute amount. So low intensity exercise may use a higher
proportion of fat relative to glycogen, but not necessarily a higher
amount. If low intensity exercise is low enough that not many calories are being used, you won't necessarily be burning more fat than a high intensity workout that is using lots of calories.