Answer: There is no valid research showing that high fructose corn syrup (HFCS) is associated health problems or weight gain. This is a great example of how popular media can manipulate or misinterpret science to stir up controversy.
Too much of ANY NUTRIENT can be unhealthy. The references and arguments often cited regarding HFCS and poor health or being overweight are based on the role of excessively high pure fructose intake in lab animals and the negative health consequences of that feeding strategy. Keep in mind super high intake of any food or nutrient can lead to poor health.
HFCS does not deliver high amounts of fructose. The name refers to the percentage of fructose to glucose in a modified corn starch. The actual fructose content is the same as or less than sugar (sucrose). As for a link between HFCS and obesity, it is not HFCS per se, but the fact that foods that contain it (junk food, sodas, and sweetened fruit juices) are eaten in excess, resulting in more calories than are needed to maintain weight. It does not matter what is in the food, if what you’re eating is excess calories, it will be stored as fat. End of story. There is absolutely no evidence showing that HFCS, as part of a sensible, proper caloric intake, causes health problems independent of any other risk associated with one's lifestyle and food choices.
All top nutrition research scientists (see January 16th, 2007 edition of Newsweek) agree that weight-related health problems are related to calorie intake vs. output and certainly not high-fructose corn syrup (HFCS). Taking into consideration economics, normal food intake and health, high-fructose corn syrup works better than most sweeteners because it is less expensive and its sweetness is greater per calorie than sucrose.
For more on HFCS and other myths, see Fact or Fiction? Enduring Fitness Myths.