Yeah, that's not entirely true. You can eat a big ol' rib-eye steak and that would not be on plan, but it wouldn't knock you out of ketosis. Not that I'm recommending that anyone eat that, of course. But only carbs will do it. Which is why Atkins folks are always in ketosis, no matter how much fat and protein they eat.
But otherwise, everyone has their own level. For some, even the 85 grams on the plan is too much to stay in ketosis (some of us who spent a long time on Atkins or other low-carb plans, for instance).
Reached goal in August 2006
Added BodyBugg in May 2009
New ticker: 136.6/123.2/130