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High fructose corn syrup the cause of obesity epidemic, new study suggests

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Bad news for the high fructose corn syrup industry.  A new study led by a Princeton University research team suggests that high fructose corn syrup may be at least partially responsible for the increase in the obesity rate in the United States.

The study published online March 18 by the journal Pharmacology, Biochemistry and Behavior showed consumption of high fructose corn syrup caused more weight gain in lab animals than table sugar when both sweeteners were consumed in equal quantity.

In addition, long term consumption of high fructose corn syrup caused abnormal increases in body fat, particularly in the abdomen, and an increase in circulating blood fats called triglycerides.  Both are signs of metabolic syndrome.

"Some people have claimed that high-fructose corn syrup is no different than other sweeteners when it comes to weight gain and obesity, but our results make it clear that this just isn't true, at least under the conditions of our tests," said Bart Hoebel, who specializes in the neuroscience of appetite, weight and sugar addiction.

Professor Hoebel said in a press release by the University that all the rats drinking high fructose corn syrup at levels well below those found in soda pop were becoming obese.  This sweetener was so effective in causing obesity that even a high-fat diet was no match for it. The high fat diet did not cause obesity in all rats.

Hoebel and colleagues did two experiments.  In one, they tested high fructose corn syrup in two groups of male rats who were using the same standard rat diet, but received drinking water with table sugar or sucrose.  The high fructose corn syrup level used in the experiment was only half as concentrated as most sodas while the sugar concentration was the same as is found in some commercial soft drinks.

What was found is that male rats drinking the high fructose corn syrup solution gained much more weight than those that drank water with table sugar.

In the second experiment, Hoebel and colleagues tested the long term effect of high fructose corn syrup on weight gain.  This time, the researchers gave one group of rats only the standard rat chow and another group a high fructose corn syrup solution in addition to the same rat chow for a period of six months.

They found rats that had access to high fructose corn syrup showed characteristic signs of the metabolic syndrome including abnormal weight gain, significant increases in circulating triglycerides and increased fat deposition - particularly visceral fat around the belly.  Male rats using high fructose corn syrup gained 48 percent more weight than those eating the normal diet.

High fructose corn syrup contains unequal amounts of glucose and fructose while table sugar or sucrose contains one molecule of glucose and one molecule of fructose.  The difference between table sugar and high fructose corn syrup is that two molecules in sugar are chemically bound while fructose and glucose in high fructose corn syrup are not bound to each other.

It is unknown why high fructose corn syrup is more likely to cause weight gain than sucrose or table sugar. But the researchers speculated that the free form of fructose is readily to be absorbed and metabolized to produce fat while glucose is largely processed for energy or stored as a carbohydrate called glucagon in the liver and muscles.

Dr. Chi-tang Ho's team at Rutgers University reported in Aug 2007 at the 234th National Meeting of the American Chemical Society that they found one single can of a HFCS sweetened soft drink contained five times higher concentration of reactive carbonyls than the concentration found in the blood of an adult with diabetes.

Dr. Ho and team tested 11 different carbonated soft drinks containing HFCS and found these beverages contained "astonishingly high" levels of reactive carbonyls.

They also found that a green tea component known as epigallocatechin gallate (EGCG) when added to the carbonated HFCS-laden soft drinks reduced the levels of reactive carbonyl species in a dose-dependent manner, by up to 50 percent.

It remains unknown whether the bad guy that causes obesity and metabolic syndrome is fructose or the reactive carbonyls present in high fructose corn syrup.  It would be interesting if the Princeton team would test to see if a mixture of fructose and glucose would differ from high fructose corn syrup.

High fructose corn syrup is not only used in soft drinks, but also in many processed foods like cereal, bread, ketchup and mayonnaise.  Americans consume 60 pounds of the sweeter per capita annually, according to the Princeton University pres release.

By David Liu and eidting by Denise Reynolds
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