I believe the reason some people react to sugar negatively is a chemical pathway called the polyol pathway.

http://en.wikipedia.org/wiki/Polyol_pathway

Not all diabetics get this BTW... I recall a science article in the past saying only genetically prone people react to sugar this way.
About 30% of diabetics. Doctors and ads would have you think all diabetics are equal but they do differ.

Type II diabetes has an surplus of insulin also... and high insulin levels, interact with the Cox-2 pathway and favor it, at the expense of the Cox-1 path which is a maintenance path. The Cox-2 path is inflammatory, and inflammation causes pain.
This reaction may be blunted by fish oil. So people who react to sugar with more pain should be on fish oil at least for a while to see if that helps.

People with poor livers, damaged livers by virus infections or alcohol, are not going to make enough glycogen or glucose on a paleo diet. These people will always crave carbs, more than others. Carbs also favor synthesis of serotonin, and as such provide a form of calming, for many. High protein diets are well known for making some people anxious, irritable and hyper.