Chapter 26 of "Dr. Atkins' New Diet Revolution"
"My stand on exercise (I applaud it and encourage it) is the least controversial part of the book. Which doesn't mean exercise isn't important for you. Not only is it an essential part of the program, but in cases of severe metabolic resistance, it's likely to be the difference between success and spinning your wheels."
[Ephasis mine]
IOW, he explains in pretty good language and terms what happens when you deprive your body of carbs, and the body is forced to use fat stores to help use the caloric value in protein.
I don't remember him going in to much detail about the importance of maintaining muscle mass and the integral connection between glycogen stores, their combustion, the actual release of fat stores from a cell, etc.
But actually the point that a pervious poster made to me was just, it's a diet book, not a fitness book. I just thought that as he was a Doctor, and took the time to explain the food intake/fuel connection he would have done the same with the food/fitness connection.