My comment below assumes you are not training hard for a triathalon, or to build lots of muscle mass...
I thought the point was to occasionally-- once a week or so-- do some short-duration full-out exercise to ensure your body's native glucagon gets burned up, thereby forcing your body into gluconeogenesis wherein it uses stored body fat to replenish those glucagon stores in the liver and elsewhere.
The idea that if you're training intensely, and eating hardly any carbs at all, you may go into ketoacidosis, which is bad news. But if you're like me, and don't get enough exercise, forcing your body into gluconeogensis to burn extra fat is a good thing. Assuming, of course, that you're also like me and you have the adipose tissue to burn.
UPDATE: To Cliff, below (threaded comments not working)
It is true that gluconeogensis occurs using certain amino acids deriving from protein. It is also true that it uses glycerol, which comes from triglycerides and the fat in our tissues.
So we are both right.
I was under the impression, though, that the process you're talking about, Cliff, was more prevalent in ketoacidosis, which will only happen in extreme cases in those that aren't diabetic. The byproducts of that result include-- I hear-- one's breath smelling of nail polish. Which certainly sounds like something I would like to avoid.
Because of your observation, Cliff, we always should ensure we are eating enough protein. But if a person is on this board they almost certainly are eating enough protein.