Joel, that was clearly used as an example to reiterate that you’ll still lose muscle even with ample calories, if there isn’t enough fat or carbs in your diet.
Pugsley, actually ketosis is protein sparing. Ketosis is metabolically simliar to starvation, and once your body adapts, it’s a very protein sparing state. Think about starvation – it’s not like there is an exponential decrease in muscle. I had data on this from one of my old classes, but can’t find it right now.
You’ll only oxidize protein for fuel when your system is running on sugar. When you make the metabolic switch to ketones as a primary fuel source, the need to convert protein to sugar isn’t needed as much. The end result is less protein oxidized in that state – muscle sparing.
As well, technically speaking, anything under about 100 g of carbs will have you showing ketones. No, probably not in your urine, but on a blood test, yes you’d show them.