Is that right? HFCS makes people fat?
I learned some interesting things while researching this blog entry. For instance, the Latin term ad libitum means "at one's pleasure" and is the source of the term "ad lib."
And I discovered that lab rats undergo something called "rapid decapitation" when it's time to check the results of an experiment.
What I did not learn was that high fructose corn syrup (HFCS) causes obesity in humans.
Princeton University recently circulated an article announcing a study, which was conducted by researchers in its psychology department and Neuroscience Institute and published in the journal "Pharmacology, Biochemistry and Behavior." In short, the study found that rats who consumed lots of HFCS became obese. So, the authors conclude, "Translated to humans, these results suggest that excessive consumption of HFCS may contribute to the incidence of obesity."
As might have been expected, the HFCS industry quickly responded, with the Corn Refiners Association pointing out several flaws in the study that undercut its conclusions.
Translating the study's reported rat intakes to human proportions, the calories gained from high fructose corn syrup would be equivalent to about 3000 kcal/day all from that single source. In comparison, adult humans consume about 2,000 calories per day from all dietary sources. Such intake levels for the study animals would be the equivalent of humans drinking a total of 20 cans of 12 ounce sodas per day - a highly unrealistic amount. Moreover, the researchers concluded that the rats gained more weight from high fructose corn syrup than they would have from sugar, yet the researchers had no proper basis for drawing this conclusion since they failed to provide sucrose controls for part of the study's short-term experiments and no sucrose controls whatsoever were present in any of the long-term experiments.
But others with less direct interest in the outcome have voiced criticism, too, most notably Marion Nestle, a professor in the Department of Nutrition, Food Studies and Public Health at New York University and author of the Food Politics blog. In her entry about the study, she writes
I can hardly believe that Princeton sent out a press release yesterday announcing the results of this rat study. The press release says: "Rats with access to high-fructose corn syrup gained significantly more weight than those with access to table sugar, even when their overall caloric intake was the same."
How they came to these conclusions is beyond me.
Among Nestle's chief complaints: Though the study claims that all the rats consumed the same number of calories, nowhere does it actually say how many calories. Plus, the whole thing seems poorly designed, with rats consuming different combinations of HFCS, sucrose and rat chow for varying periods, making straight comparisons difficult.
I agree with Nestle and the corn refiners: This study's not convincing enough to support its statement that
In summary, rats maintained on a diet rich in HFCS for 6 or 7 months show abnormal weight gain, increased circulating TG [triglycerides] and augmented fat deposition. All of these factors indicate obesity. Thus, over-consumption of HFCS could very well be a major factor in the "obesity epidemic," which correlates with the upsurge in the use of HFCS.
I contacted Bart Hoebel, the professor at Princeton who worked with the research team and whose name appears on the paper. While I believe that a published scientific paper should stand on its own, with no added explanation from the researchers, I would really like to understand this study better. To see the questions I e-mailed him and his answers, keep reading on the next page.
The bottom line: Drinks sweetened by sugar or HFCS contain calories, and consuming too many calories can make you fat.
Lab rats don't get to choose what they eat and drink. But people do.
Rats can't tweet, but we can! Look for me and the other Local Living writers at @wposthome/local-living. And keep track of my "Me Minus 10" effort to lose 10 pounds before I turn 50 at twitter.com/jhuget.
JLH: Can you explain, for the nonscientific folks out there, how reliably rat-study results translate to humans?
BH: The rat is much like the human in regard to feeding behavior and basic metabolism. Rats evolved eating a diet something like ours; in some cases our own garbage. Thus the rat is a reasonable "animal model" of human feeding behavior in many cases. There are some cases in which rats taste things differently and metabolize food differently than people. Rat studies need to be reproduced in people whenever possible, after the critical variables have been established using laboratory animals.... To see a review of all fructose studies in animals and people, I recommend [George Bray's article in the February 2010 issue of Current Opinion in Lipidology, "Soft drink consumption and obesity: it is all about fructose."] However, note that many human studies compare pure fructose with other sugars, which is not what we did. We offered rats high-fructose corn syrup or sucrose, which are the common ingredients in soft drinks. The results do not apply directly to humans, but strongly suggest the need for more experiments along these lines.
JLH: Marion Nestle criticized the study for not being clear about the rats' calorie consumption. Can you speak to that?
BH: She says: Although the authors say calorie intake was the same, they do not report calories consumed.
We say: Caloric intake was reported in the Results section for Experiment 1.
She says: nor do they discuss how they determined that calorie intake was the same.
We say: In the Methods section we explain that we measured HFCS, sucrose and chow intake daily. We computed the calories consumed, which is also described in the Methods section.
She says: This is an important oversight because measuring the caloric intake of lab rats is notoriously difficult to do (they are messy).
We say: We do not see any oversight. The drinking tubes had an anti-drip device built in and we collected spillage for the food pellets for accuracy. We reported the caloric intake and the standard error, which shows the variability in intake for a given group. This is reported in the Results section.
JLH: Also, many critics felt the study was designed poorly, never pitting HFCS directly against sucrose and testing for what seemed to be almost arbitrary time periods. Again, anything you could offer to help us better understand those issues would be helpful.
BH: Not true. In male HFCS was compared directly to sucrose in Exp 1. In Exp. 2, we compared HFCS to sucrose in females, and we describe in the paper our reasons for using 12-h and ad libitum access to sucrose vs. HFCS. We were interested in comparing the effects of limited vs. continuous access.
JLH: Finally, something about the way the study was written sounds as though researchers set out to link HFCS to obesity, not to determine whether such a link exists. It feels as though the dots aren't all connected very clearly. Can you address that, please?
BH: The study was designed to explore the comparison of HFCS with sucrose and at the same time to compare 24 h access with 12 hr access, plus males with females. Keep in mind that this is research, and one does not know which will be the key results when starting out. We discovered that male rats drinking HFCS were heavier than the matched sucrose controls in Exp 1 and heavier than the other groups in Exp 2. Regarding females, again the HFCS rats were the heaviest; although the sucrose control group had sugar available for less time per day, we had reason to think this was not a critical variable based on our prior publications in which 12 and 24 hr access to sucrose leads to the same body weights. Moreover the females, like the males, showed elevated triglycerides and increased fat deposits. This is all explained in the article for anyone who wants to study it carefully.
Jennifer LaRue Huget
March 26, 2010; 7:00 AM ET
Categories: Is That Right? , Me Minus 10 , Nutrition and Fitness , Obesity
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