No, but transitions "into" and "out of" ketosis are rough. Getting into keto, most people get sick - this is a phenomenon called "keto flu" Going off keto, I know I get headaches and stomachaches from the sugars, but this is not as widespread Honestly /r/keto on reddit is a good resource, especially their wiki... also /r/ketoscience ... be forewarned a bunch of those are fat fucks losing weight with keto, which works better for obese until they're "fit enough to for exercise to show progress" so there are "progress" photos which I avoid