Very high ketone levels can be toxic, making the blood more acid, and may damage such organs as the kidneys and liver.
Hmm. I'm not 100% sure that's the best description of ketosis I've ever read.
Whoever wrote it was confusing benign dietary ketosis with ketoacidosis. The kind of ketosis that we get into on low carb diets isn't toxic and it certainly doesn't damage kidneys and liver - unlike ketoacidosis, which is something that can afflict those who suffer from diabetes (and
would cause acidosis and organ damage).
Sigh. Anyway, back to the original question:
The problem, as Enough has said, is that you'll gain something in the region of 5-7 pounds if you consume carby stuff whilst off the diet. That's fine if you know it's going to happen and can deal with the 'head stuff' that comes with rapid weight gain. And if you're pretty sure that you can handle going straight back on the diet again, then you're right, you'll be fine.
If...
Because the thing is, I've noticed that each time you get back into ketosis is different. Sometimes it's an absolute breeze and you wonder what everyone makes all the fuss about. Other times, you get the headache that lasts for days on end... I've experienced it both ways, that's for sure. And it's easy to kid yourself that you'll find it easy to get back on the diet when you're still in the throes of ketosis. Unfortunately, once you've had a few pesky carbs, it doesn't seem so easy.
You might be one of the lucky ones who really can handle the switch to and from Cambridge relatively painlessly. To be brutally honest, most people find it very difficult - you only have to look at the number of folk who start Cambridge before Christmas, do well and come off 'for Christmas' then find it very very difficult to get back on track in the New Year.