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How Corn Syrup Might Be Making Us Hungry–and Fat

The views expressed are those of the author and are not necessarily those of Scientific American.


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fructose brain hunger obesity

Image courtesy of iStockphoto/bttoro

Grocery store aisles are awash in foods and beverages that contain high-fructose corn syrup. It is common in sodas and crops up in everything from ketchup to snack bars. This cheap sweetener has been an increasingly popular additive in recent decades and has often been fingered as a driver of the obesity epidemic.

These fears may be well founded. Fructose, a new study finds, has a marked affect on the brain region that regulates appetite, suggesting that corn syrup and other forms of fructose might encourage over-eating to a greater degree than glucose. Table sugar has both fructose and glucose, but high-fructose corn syrup, as the name suggests, contains a higher proportion of fructose.

To test how fructose affects the brain, researchers studied 20 healthy adult volunteers. While the test subjects consumed sweetened beverages, the researchers used fMRIs (functional magnetic resonance imaging) to measure the response of the hypothalamus, which helps regulate many hunger-related signals, as well as reward and motivation processing.

Volunteers received a 300-milliliter cherry-flavored drink sweetened with 75 grams (equivalent to about 300 calories) of fructose as well as the same drink sweetened with the same amount of glucose. These different drinks were given, in random order, at sessions one to eight months apart. The researchers also took blood samples at various time points and asked volunteers to rate their feelings of hunger and fullness.

Subjects showed substantial differences in their hypothalamic activity after consuming the fructose-sweetened beverage versus the one sweetened by glucose within 15 minutes. Glucose lowered the activity of the hypothalamus but fructose actually prompted a small spike to this area. As might be expected from these results, the glucose drink alone increased the feelings of fullness reported by volunteers, which indicates that they would be less likely to consume more calories after having something sweetened with glucose than something sweetened with more fructose.

Fructose and glucose look similar molecularly, but fructose is metabolized differently by the body and prompts the body to secrete less insulin than does glucose (insulin plays a role in telling the body to feel full and in dulling the reward the body gets from food). Fructose also fails to reduce the amount of circulating ghrelin (a hunger-signaling hormone) as much as glucose does. (Animal studies have shown that fructose can, indeed, cross the blood-brain barrier and be metabolized in the hypothalamus.) Previous studies have shown that this effect was pronounced in animal models.

The study, led by Kathleen Page, of Yale University School of Medicine and published online January 1 in JAMA, The Journal of the American Medical Association, was small and was not able to pinpoint precise neural circuits that might be affected by the sweeteners. But the results, along with other research, suggest that, thanks to the “advances in food processing and economic forces” that have boosted the intake of fructose, added sugar and high-fructose corn syrup are “indeed extending the supersizing concept to the population’s collective waistlines,” wrote Jonathan Purnell, of the Division of Endocrinology, Diabetes, and Clinical Nutrition, and Damien Fair, of the Department of Behavioral Neuroscience, both of Oregon Health & Sciences University in Portland, who coauthored an essay that appeared in the same issue of JAMA.

Could fructose consumption alone really be playing such an outsized role in expanding our pant sizes? “A common counterargument is that it is the excess calories that are important, not the food. Simply put: just eat less,” Purnell and Fair noted. “The reality, however, is that hunger and fullness are major determinants of how much humans eat, just as thirst determines how much humans drink. These sensations cannot simply be willed away or ignored.” In order to eat less (and consume fewer calories overall), they argued, then, one should avoid foods or ingredients that fail to satisfy hunger. And that, according to the results from the new study, would mean those fructose-sweetened foods—and drinks.

Katherine Harmon Courage About the Author: Katherine Harmon Courage is a freelance writer and contributing editor for Scientific American. Her book Octopus! The Most Mysterious Creature In the Sea is out now from Penguin/Current. Follow on Twitter @KHCourage.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. JDoors 6:34 pm 01/1/2013

    “Volunteers received a 300-milliliter cherry-flavored drink sweetened with 75 grams (equivalent to about 300 calories) of fructose as well as the same drink sweetened with the same amount of glucose.”

    Are equal weights of fructose and glucose used interchangeably in food?

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  2. 2. DavidGillespiesBigFatLies 7:05 pm 01/1/2013

    Interesting preliminary study and proof of concept, now we need to test in realistic dosages and in forms that people actually eat. This would requires 150g of sucrose or slightly less HFCS!

    Also interesting to see what effect the glucose and fructose would have together i.e. the way most people take in it!

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  3. 3. johan01 8:04 pm 01/1/2013

    upto I looked at the check for $5703, I accept that my cousin woz like they say realey earning money part time on there computar.. there mums best friend has been doing this 4 only 17 months and just repaid the debts on their villa and got themselves a Toyota. read more at, ….. BIT40.ℂOℳ

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  4. 4. skass 10:37 pm 01/1/2013

    “Table sugar has both fructose and glucose, but high-fructose corn syrup, as the name suggests, contains a higher proportion of fructose.”

    That’s incorrect. Table sugar is 50% fructose. The high-fructose corn syrup commonly used in foods and drinks is either 42% or 55% fructose. HFCS is only called “high-fructose” because it contains more fructose than unprocessed corn syrup.

    This just-published study compared glucose to fructose. It didn’t study corn syrup, sugar, or HFCS, so it’s irresponsible to quote this research as an indictment of corn syrup or HFCS.

    If this study tells us anything about corn syrup, it tells us that we should be consuming more of it in place of sugar, not less (specifically, unprocessed corn syrup or 42%-fructose HFCS). The study says nothing to suggest HFCS is worse than sugar.

    If fructose turns out to be a real villain, don’t go after HFCS. Instead, go after apple, pear, and grape juices. They’re commonly found in “all natural” products and juice drinks aimed at children, but they’re higher in fructose than HFCS.

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  5. 5. hanbroekman 6:42 am 01/2/2013

    SciAm said: “Fructose, a new study finds, has a marked affect on the brain region that regulates appetite, ”
    Should I start worrying when SciAm mixes up affect and effect?

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  6. 6. straightbourbon 9:28 am 01/2/2013

    skass is 100% correct! Thank you to skass for making the comment above. I was thinking the exact same thing when I read this article – “HFCS is only called “high-fructose” because it contains more fructose than unprocessed corn syrup.”

    While skass comments are correct, the article is indeed incorrect when stating, “Table sugar has both fructose and glucose, but high-fructose corn syrup, as the name suggests, contains a higher proportion of fructose.”

    Who is this author, Katherine Harmon? And WHY is she writing for Sci-Am? I have been a subscriber and avid reader since the early eighties. I am really disappointed that Sci-Am would have these kinds of inaccuracies.

    This article was also picked up by Yahoo! and is shown on the Yahoo! home page. At least us scientific types know the errors when we see them. Now Yahoo! readers will be further mislead by this misinformation. Sci-Am should NOT be the source of incorrect information in poorly written articles!

    Apparently, the person that wrote this article has a very weak grasp of chemistry, and what the similarities and differences are between sucrose, glucose, and fructose. She should go back to high school.

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  7. 7. Kombarde 10:39 am 01/2/2013

    That’s weird. I was told in school that sucrose is more harmful that fructose which is about 45% sweeter in addition. Thus it is better to derive sweetness from an apple/orange rather than a cake.
    May be it is a new turn of green marketing promoting “good” and expensive apple fructose instead of “bad” cheap corn fructose.
    I am new here. Is it scientific or populist website?

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  8. 8. schlenk55 10:39 am 01/2/2013

    High fructose corn syrup is the #2 ingredient in infant formula. The first ingredient is cow or soy milk… both highly allergenic foods to many humans.

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  9. 9. John Weaver MD 1:03 pm 01/2/2013

    I guess I need to add this article to my list of Inconvenient Truths about fructose.

    1. Food is digested down to molecules before entering our blood. This means your cells don’t distinguish between fructose derived from sucrose, high fructose corn syrup, agave or an apple.
    2. It is fructose molecules that make high fructose corn syrup unhealthy.
    3. It is fructose molecules that make sucrose (cane & beet sugar) unhealthy
    4. It is fructose molecules in fruit (about 25-50% by dry weight of part we eat) that make whole fruit at best a special treat to eat sparingly.
    5. All the essential nutrients in fruits (such as potassium, vitamin-C etc.) and most phytochemicals that can have therapeutic effects can also be obtained in safer and less expensive foods.
    6. Why worry about a little fructose in a meal? A little fructose changes liver enzymes to turn more of any carbohydrate, not just fructose into fatty acids (triglycerides). As a result, even after eating sufficient calories, you are still hungry.
    7. We don’t need to eat any fructose. Cells do need fructose for making genetic material when they replicate. Gut lining cells replicate every three days cells that line blood vessels replicate every 5 years so not much fructose is needed. So where do cells get fructose if we don’t eat it?
    8. When cells need fructose to replicate they make only what is needed from glucose. This is nice example of a “just in time supply system” which is ideal when you don’t want a reactive chemical which is 7 times more reactive than glucose sitting around. Even glucose is reactive but the body has safe storage (glycogen) and elaborate control system to keep blood glucose as low as possible without creating problems.
    9. High blood glucose as seen in diabetes is unhealthy because it creates an excess of fructose in cells. High blood glucose pushes the sorbitol pathway to form excess fructose in all cells. So the bad effects of diabetes are really caused by elevated fructose in cells.
    10. So why is excess fructose in a cell a problem? It forms glyceraldehyde. Glyceraldehyde is the most reactive sugar in the body. Glyceraldehyde can react directly with cell messengers and nuclear material. Glyceraldehyde is a small molecule and can leave the cell and reacts with lysine in blood to form a toxic advanced glycation end product or TAGE. TAGE is recognized by our innate immune system as a foreign molecule that via RAGE receptors causes cell INFLAMMATION. TAGE also increases VegF. VegF is involved in over 60 chronic diseases. The bottom line… Fructose (from diet or elevated blood glucose) via effects of glyceraldehyde, TAGE, RAGE and VegF increases by 10 to 20 fold the expression of many noninfectious diseases.
    John Weaver MD

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  10. 10. straightbourbon 1:28 pm 01/2/2013

    I understand how fructose can be problematic in many ways. However, the fructose in sucrose is just as problematic for the body as the fructose in High Fructose Corn Syrup.

    And once again, just to be clear – the article may be correct on some points, but it is in fact incorrect to say that High Fructose Corn Syrup contains more fructose than sucrose does.

    As skass correctly points out in his comments above, “[The article is] incorrect. Table sugar is 50% fructose. The high-fructose corn syrup commonly used in foods and drinks is either 42% or 55% fructose. HFCS is only called “high-fructose” because it contains more fructose than unprocessed corn syrup.”

    The takeaway from all of this is that the author’s assertion that “high-fructose corn syrup, as the name suggests, contains a higher proportion of fructose” is a false assertion.

    If we consume to much fructose from HFCS because HFCS is cheap and it drives down the price of sucrose, then that is a separate issue. As far as anyone medically or scientifically knows, consuming too much sucrose has the same effect on the body as consuming too much HFCS. This is because sucrose and HFCS both contain about the same proportions of glucose to fructose, which is 50% either way.

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  11. 11. striped_burrito 2:11 pm 01/2/2013

    As the commentator above points out, HFCS does NOT contain more fructose than table sugar. Is it too much to expect a once highly regarded magazine like Sci Am to now get even basic facts right? I have read many reviewers say that Sci Am has declined in quality since the 80s. This article simply shores up that observation. The author of this article has a master’s degree in journalism. That does not preclude her from writing about science but it does make it incumbent on her to read up on basic chemistry and biology.

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  12. 12. SteveinOG 2:13 pm 01/2/2013

    Straightboubon, so are you saying that the 45% to 58% of HFCS “unprocessed corn syrup” has no caloric content?

    The relevance of this experiment is muddled by the researchers’ decision to compare pure fructose to pure glucose, neither of which is a food additive on its own. They should compare HFCS to cane sugar.

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  13. 13. psguy2002 3:18 pm 01/2/2013

    The biggest difference between HFCS and sugar, though, is that HFCS has an unbound molecular structure, meaning the energy is *immediately* available to the body with ZERO metabolic steps. Sugar requires a metabolic step to make the energy available to the body. That change ALONE shows that sugar and HFCS are not “the same”.

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  14. 14. outsidethebox 5:27 pm 01/2/2013

    @ psguy: Do you mean sucrose when you say sugar? Or dextrose? Or both?

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  15. 15. sofistek 6:16 pm 01/2/2013

    Take time to watch a video talk by Dr. Robert Lustig: “Sugar: The Bitter Truth” at http://www.youtube.com/watch?v=dBnniua6-oM

    It’s hard to understand how this nonsense about low fat foods ever got propagated to the medical community and public health departments.

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  16. 16. Hayduke2000 10:50 pm 01/2/2013

    Eat real food, not food products. Eat only what your grandmother woud recognize as food.

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  17. 17. kkkss 11:23 pm 01/2/2013

    There are a few different HFCS.
    One is HFCS-42, and another is HFCS-55.
    For HFCS-55, the major use is in the beverage industry, which demands over 90 percent of total domestic deliveries.

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  18. 18. ronyrao 1:03 am 01/3/2013

    We don’t need to eat any fructose in order to stop the fat.
    http://www.solarinverter-au.com/news/polysilicon-pv%20industry/

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  19. 19. DavidGillespiesBigFatLies 5:40 am 01/3/2013

    John Weaver MD – surely Scientific American is a worthy enough website for you to provide evidence for your assertions – especially when considering the old saying ‘it is the poison that makes the dose!’

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  20. 20. Paul_D_Heikkila 9:12 am 01/3/2013

    If fructose prevents you from feeling full, but sucrose makes you feel full, wouldn’t you expect that Cubans, who consumer lots of sugar, would be thin? However, obesity in Cuba is a health problem as it is in fructose eating countries.

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  21. 21. eddiequest 4:45 pm 01/3/2013

    Perhaps the SciAm editors should consult all commenters BEFORE publishing?

    Link to this
  22. 22. DavidGillespiesBigFatLies 6:10 am 01/4/2013

    Did anyone read the study? How about this line “There was NO significant difference between glucose vs fructose ingestion on predrink-postdrink changes in hunger, fullness or satiety”.

    You can infer all you want from bloodflow to different areas – in practical terms – it didn’t cut it!

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  23. 23. ftmarin 6:37 pm 01/6/2013

    I agree with those who argue that comparison of feedings of pure glucose or pure fructose do not tell us anything about HFCS (which, as noted above, is not terribly different from sucrose in its fructose content).

    The fact that the difference was ‘documented’ by fMRI should also give pause (remember the dead salmon – http://prefrontal.org/files/posters/Bennett-Salmon-2009.pdf)

    When editors of JAMA equivocate on the importance of the direction of change, and go on to suggest these findings support the notion that fructose exposure modulates appetite regulation, one can only wonder. Particularly when, as pointed out by others above, the study demonstrates no significant difference in hunger, fullness, or satiety.

    While these preliminary results might, at best, suggest further study is warranted, one should hope that the needed studies were done before publication.

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  24. 24. bucketofsquid 11:53 am 01/7/2013

    Just a couple of things;
    1 – This is a blog post and not an article. No one other than the blogger edited this. Getting up tight about someone’s opinion just makes you look like a jerk. If people could only have opinions that are factually accurate, Fox News and MSNBC would be out of business.

    2 – The issue may not be fructose itself but it is certainly concerning that sugar is added to pretty much every food you eat certainly is. I recently bought a couple of things I thought were fairly low sugar – beef jerky and blueberries. I was quite disgusted to see that the ingredients list on both had high fructose corn syrup as the second item. Why would blue berries need sugar added? And who in their right mind wants sugary jerky? I live in a state that gets a lot of revenue from corn for both ethanol and high fructose corn syrup. The same corn growers (including some relatives and in-laws) whine and complain about increased gas prices from the bad ratio of petroleum to corn for ethanol. They also whine about providing health care for the people they made fat and unhealthy. I’m not impressed. If you don’t like the consequences of your actions then do something different.

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  25. 25. Constant Crisis News & Opinion 11:30 pm 03/17/2013

    In episode 47 of the Constant Crisis News & Opinion self-help and humor podcast, Ham & Chuck manage to draw a UNCANNY comparison between the USDA (which is managing to cause obesity and fight obesity at the same time) and Mike Rios, convicted pimp, fraudster and panderer and former member of the Moreno Valley, California School Board. You have to hear it to understand it, and even then, you know, it might still be a little confusing. Coverage starts at 15:09. Listen for free at http://wp.me/p2BT86-93.

    Link to this

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