Study of high-fructose corn syrup stirs critics

In late February, the journal Pharmacology, Biochemistry, and Behavior published an interesting study from Princeton psychology professor Bart Hoebel’s lab: Over an eight-week period, rats that consumed high-fructose corn syrup, dissolved in water, gained significantly more weight than rats that consumed a regular sugar-and-water solution, even though they had the same calorie intake. In a longer version of the experiment, rats fed high-fructose corn syrup also had more abdominal fat and elevated levels of triglycerides, two symptoms associated with obesity.

High-fructose corn syrup is widely used as a sugar substitute, in foods ranging from soft drinks to Wonder Bread, and its prevalence has been a hot-button nutrition issue.  

Hoebel’s research went largely unnoticed until March 22, when a University press release announced the findings. In the week that followed, news organizations like CNN and The Washington Post picked up the story, and some 200,000 people viewed the article on Princeton’s Web site. Critics quickly weighed in — mostly on blogs — questioning the study’s methods and its meaning. One common complaint was that in highlighting the ill effects of high-fructose corn syrup, Hoebel seemed to absolve sugar as a contributor to obesity.

Hoebel, who admits he was surprised by the volume of responses, tried to clarify and explain the study, replying to bloggers and individual e-mailers with help from lead author Miriam Bocarsly ’06, a Princeton graduate student.  

On the blog of New York University nutrition professor Marion Nestle, for example, Hoebel agreed that “sucrose can also increase body weight,” but noted that in this specific study, a 10 percent sucrose solution did not cause obesity, while an 8 percent high-fructose corn syrup solution did.  

Why the difference? It may be that the chemical structures of the two sweeteners cause them to be metabolized in different ways, Hoebel said. In sucrose, each fructose molecule is bound to a glucose molecule, while in high-fructose corn syrup, the fructose molecules are free and unbound. But exactly how that translates into weight gain remains unclear. “The one thing everybody agrees on is that we need more research,” Hoebel said.

Hoebel, a neuroscientist, aims to shed light on the neural mechanisms in the brain that control appetite. Follow-up work could include a study that measures the combined effects of a high-fat diet and the consumption of high-­fructose corn syrup on the brain and behavior.