Compared to animals eating only rat chow, rats on a diet rich in high-fructose corn syrup showed characteristic signs of a dangerous condition known in humans as the metabolic syndrome, including abnormal weight gain, significant increases in circulating triglycerides and augmented fat deposition, especially visceral fat around the belly.

And:

When male rats were given water sweetened with high-fructose corn syrup in addition to a standard diet of rat chow, the animals gained much more weight than male rats that received water sweetened with table sugar, or sucrose, along with the standard diet.

Don’t act shocked or anything.