It's not just carbs it's basically pure sugar. And sometimes the type of sugar can be more potent. One thing that's often a "natural flavor" in vitamins is dextrose, a super potent sugary item. It will throw anyone out and spike your blood sugar like a demon.

It does take days to convert to ketosis. Once you stop the process with pretty much any serious blood sugar spike you have to start again. 50-100 calories is no joke s far as sugar goes.