[jnwatson]

A few parts of your body can't operate on ketones, so there's a backup mechanism to produce glucose from protein (from muscle breakdown, if necessary) called gluconeogenesis.

However, There's no evidence I've see that gluconeogenesis can kick you out of ketosis. As far as I know, gluconeogensis is demand-driven, not supply-driven, so there won't be any extra glucose running around for your ketone-consuming cells to use, regardless of your protein intake.

Disclaimer: I'm not a nutritionist or biologist.