By Nicci Micco, April 13, 2010 - 4:35pm
On April 9, the folks at Grist.com reported that they’d contacted Princeton researcher Bart Hoebel to address objections raised by physiologist Karen Teff, P.h.D of the Monell Chemical Senses Center in my previous blog post about Hoebel’s new study on high-fructose corn syrup causing weight gain in rats. In fact, we’d posted Dr. Hoebel’s comments on our site 8 days earlier on April 1. If you missed Hoebel’s response, here it is below.
(And if you’re still hungry for more on the controversy around this new study, check out this blog on Hoebel’s study from our nutrition and health advisory board member Marion Nestle, Ph.D., M.P.H., professor of Nutrition, Food Studies and Public Health at New York University. Please note that you can also see Dr. Hoebel’s responses to Nestle’s critiques here too.)
No doubt that the science on HFCS is confusing. Still, EatingWell’s practical advice on the topic is this: minimize your intake of added sugars in all forms (HFCS, table sugar, honey, etc.). What’s the problem with sugars? Find out here.
Response from Bart Hoebel on EatingWell.com:
According to Nicci Micco in a blog on Eating Well, Karen Teff of the Monell Chemical Senses Center found fault with our study of high-fructose corn syrup (HFCS) in rats. Here are her four points and our responses to them. I hope you find this helpful. Bart Hoebel, Princeton University
Comment #1: The solutions of HFCS and sucrose used in all the studies—there were a few—in the Princeton report provided different levels of calories. (The HFCS, in fact, was lower in calories.)
Response: It is correct that the solutions of HFCS and sucrose were not offered as calorically equivalent. We note this in the Methods section of the paper. However, it is important to note that the HFCS-consuming rats in Experiment 1, the short-term (2-month) study, showed greater gains in body weight while taking in fewer calories of sugar compared to the groups consuming sucrose. This led us to hypothesize that there might be something different about the way HFCS affects the body. Thus, we conducted Experiment 2, the long-term (6-month) study, and measurements showed that increased triglyceride levels and increased body fat were seen in the rats with access to HFCS, but not sucrose.
Comment #2: In one of the studies, the authors reported that male rats had a higher body weight after being exposed to 12 hours of access to the HFCS plus their typical rat chow compared to 1) standard chow alone, 2) 12 hours of access to sucrose with chow, and 3) 24 hours of access to sucrose with chow. However, they did not report or do the statistics on the change in weight. Thus, this is meaningless and poorly controlled.
Response: One of the groups listed above is cited incorrectly; group 3 had 24 hours of HFCS and chow access (no sucrose access). As stated in the Methods section, the males in the three groups of Experiment 1 were “weight-matched.” That means the average (mean) weight of the rats in each group started out the same. Therefore the end-point body weights reported are in fact accurate representations of the mean body weight change. Ergo, the statistics were done on the appropriate measure. The result is meaningful and well controlled, given the use of not one but three comparison groups.
Comment #3: In a second experiment, they compared chow to chow-plus-HFCS for 24 hours and chow-plus-HFCS for 12 hours and found that access to the HFCS increased body weight. So what? Again, meaningless. This is like taking two groups of people, giving them the same diet but allowing one group to drink sweetened soda whenever they liked. Of course, they will gain weight because they are ingesting more calories. These findings have nothing to do with the controversy between sucrose and high-fructose corn syrup.
Response: The result is, in fact, meaningful. As cited in the Discussion section, we have previously shown that the rats are able to compensate for the excess calories obtained when drinking 10% sucrose by taking fewer calories of chow and thereby maintaining a normal body weight. Therefore, we thought it was interesting and important to report that long-term access to HFCS causes rats to become overweight, whereas access to 10% sucrose does not. While comparisons were made to sucrose in some of the studies, this was not the sole focus of the paper. Rather, we were interested in seeing the effects of HFCS on body weight and obesogenic characteristics, and there were other variables of interest that were studied (as described in the response to the next comment).
Comment #4: Finally, in a third study, they show body weight as a percent of baseline (this is appropriate) and show that rats that had free access to both chow and HFCS gained a tiny bit more weight than chow alone, 12 hours of HFCS or 12 hours of sucrose. They did not compare it to the control of 24 hours of access to sucrose.
Response: The statistical test (Repeated Measures Analysis of Variance) did show an overall significant difference between female rats with HFCS to drink 24-hr per day and the groups with chow alone or 12-hr access to sucrose, as described in the Results section. We did not compare 24-hour HFCS vs. 24-hour sucrose in this study because 1) in our previous studies (with both male and female rats) we have noted that rats with 24-hour access to 10% sucrose do not gain significantly more weight than chow-fed controls, and 2) in addition to comparing HFCS to sucrose, we were interested in the effects of limited (12-hour) access to HFCS to see if it would cause bingeing that might enhance HFCS intake or body weight. Further, we chose to focus on assessing 12-hour access as a variable because we did not know the effect of 12-hour vs. 24-hour HFCS access in female rats. This was of interest to us in light of the findings in Experiment 1 in males where we made that comparison, and because our laboratory has a long-standing interest in the effects of binge eating of palatable food. We explain and give the rationale for the choice of these variables in the Methods section. So, yes the females drinking 24-hr HFCS showed a statistically significant increase in body weight. It is important and meaningful because these females had significantly heavier fat pads in the abdominal and uterine areas. They also had higher blood triglyceride levels than the other groups, which may have contributed to the body weight and body fat characteristics of obesity.
Our study in laboratory rats complements the growing body of literature suggesting that HFCS affects body weight and some obesogenic parameters. We cite in our paper additional evidence reported by other groups that supports our findings, and also acknowledge studies that suggest that HFCS does not affect body weight in ways different than that of sucrose. We acknowledge in the paper that at higher concentrations (e.g., 32%) sucrose has been shown to increase body weight. We are claiming, however, that at the concentrations we compared in this study, HFCS causes characteristics of obesity. The data show that both male and female rats are (1) overweight, (2) have heavier fat pads, particularly in the abdominal area, and (3) have elevated circulating triglyceride levels.
For more information and references on this topic, as studied in both animals and humans, see a review published this year by George Bray, Curr Opin Lipidol. 2010 Feb;21(1):51-7. "Soft drink consumption and obesity: it is all about fructose."