Candy a good calorie substitute?

i heard something strange the other day; someone told me that if you take in X amount of calories, its better for that amount to be sugar based (obviously not entirely though) rather than fat or carb based because molecularly sugar is simpler and your body will more easily burn them than fat molecules. i knew a few anorexic ppl in hgh school who lived off gummy bears so i can kinda see that, but is there any truth to that?