Well, today I got up and found there wasn't a hell of a lot to eat - food, I mean. Just crap like bread and jam. So I decided to live a day in the life of your average person, nutritionally. The only thing I couldn't replicate was cereal for breakfast, as we didn't have any.
I lived on sandwiches, with high glycemic things like apricot jam. Toast with honey. Milo with sugar.
The results? Pretty much as you'd expect. I didn't have a huge loss of energy, but I think thats due to insulin sensitivity gained by the paleo diet. The insulin cycle kept me hungry every couple of hours, to be superficially met with more carbohydrates - making me hungry again in a couple of hours. By the end of the day, I was visibly (to me) fatter!
This is nothing new, just a reinforcement of old. It's no wonder so many people get fat, with doctors prescribing cereal and other horse-food as things omnivores should be eating!