In this interview, (from 41:29 to 43:36), Dr. Peat suggests a mechanism by which HFCS may be more harmful than sucrose, based on this meeting abstract. Note that these links do not offer much substance to support this theory, though it seems plausible.
I have transcribed the relevant part of the interview below (some editing for clarity):
Peat: "A study at UCLA that came out last summer analyzed [high fructose corn syrup]. They chemically tested it and found that it contained just the amount of fructose and glucose that it was claimed to have. [However, upon hydrolyzing it, they] found that it contained polysaccharides (starch-like material) containing 4 to 5 times the amount of calories that the original sugar had...These polysaccharides aren't easily digested by our human enzymes and are likely to feed bacteria lower in the intestine that produce fermentation products (including lactic acid), which are responsible for causing the intestine to increase its already great production of seratonin and to cause it to be absorbed into the circulation in quantities enough to affect behavior. Anxiety, for example, is increased in animals in proportion to the fermentation of these starch-like molecules. I suspect that the starchy materials in the corn sweetener are pretty directly related to increased exposure to seratonin."
This runs counter to the prevalent notion that high fructose corn syrup is identical to sucrose. Thoughts?