HFCS

http://recipes.howstuffworks.com/high-fructose-corn-syrup2.htm

Unlike glucose, which is metabolized a number of ways by your body, fructose is only metabolized by your liver. When the liver receives more fructose than it can handle, the excess sugars are turned into fats in the form of triglycerides, which are harmful to your arteries and your heart.

The biggest problem is that HFCS is being added to food items that don't normally have sugar and that you wouldn't even describe as sweet -- crackers, for instance. So, not only are we chugging down lots of sugars with our sodas, but your PBJ sandwich could have HFCS in each of its three ingredients. Meal after meal, day after day, all of this extra sugar adds up, and that, and not necessarily the qualities of HFCS itself, is likely one reason why rates for obesity and diabetes have climbed since the introduction of HFCS. (Other factors are in play as well, such as decreased activity and exercise levels and increased fat consumption.)
So what can we do? Well, for starters, do everything you're already supposed to do. Get regular exercise, watch your fat intake and get regular medical checkups. Next, it wouldn't hurt to mimic the practices of those strange (and rare) individuals in grocery-store aisles who read the labels of the food they are purchasing. Once you get in this habit, you will likely be shocked to learn just how much of your regular grocery purchases contain high-fructose corn syrup. If nearly all of your food contains concentrated sugars, it stands to reason that you'll be eating too many sugars. And if you want to go crazy, eat some fruits and veggies. You'll get all the glucose you need (not much), and these healthier alternatives will take the place of the less healthy foods now flooding our markets and grocery stores.