Not all sugars have an equal effect on obesity

A new study suggests that consuming fructose containing sweeteners including high fructose corn syrup (HFCS) and sucrose in beverages or processed food may increase the odds for a person to become obese.

WEDNESDAY June 25, 2008 (foodconsumer.org) -- A new study suggests that consuming fructose containing sweeteners including high fructose corn syrup (HFCS) and sucrose in beverages or processed food may increase the odds for a person to become obese.

The study showed that obese and overweight people who had an intake of about 15 percent of calories from pure fructose for a period of as short as ten weeks gained 1.5 kilograms in weight and increased their intra-abdominal fat.

Intra-abdominal fat is the type that wraps around internal organs and causes a pot belly; it has been linked to an increased risk of diabetes and cardiovascular disease.

In comparison, the same amount of weight gain was also observed in a group of obese and overweight people who ate glucose, but the increase in intra-abdominal fat did not occur in the group.

Glucose is the basic compound found in complex carbohydrates like grain starch.

The study was conducted by Peter Havel et al at the University of California Davis, and the results were presented at a meeting of the Endocrine Society in San Francisco last week.

Fructose in HFCS, which is widely used in soft drinks and heavily consumed by Americans, has long been suspected of being a culprit for the ever-increasing obesity epidemic in the United States.  

Studies showed that people are not sensitive to fructose. Even after consuming large quantities of it they do not have a full feeling, resulting in their continuing to eat it: a conceivable way for a person to become obese or overweight.

Fructose-containing HFCS has also been found to cause an oxidative stress in the body, and circulating reports suggest that fructose and HFCS trigger insulin resistance and diabetes.

The study was meant to examine the effect of pure fructose on weight gain in obese and overweight people. Two phrases of key words that should be remembered are PURE fructose and obese and overweight people.

In the study, the researchers asked 33 overweight and obese adults to go on a diet consisting of 30 percent fat, 55 percent complex carbohydrates and 15 percent protein for a period of two weeks.

Afterwards, they told participants to use a diet in which 25 percent of their calories were coming from either fructose or glucose for a further 10 weeks.

People in both groups gained an average 1.5 kilograms in weight, the study found. But the types of fat each group gained differed, with only the fructose group gaining the risky type of fat associated with heart disease.

Additionally, those who consumed fructose also had raised levels of fatty triglycerides, which get deposited as intra-abdominal fat and cholesterol, according to a statement by New Scientist. In this group, insulin sensitivity fell by 20 percent.  

None of these effects were seen in the group consuming glucose.

Because the study used pure fructose, it is not known if the results would apply to HFCS or sucrose.

"The question is, what is the amount of HFCS or normal sugar you need to consume to get these effects?" said Havel, who suggested that people with metabolic syndrome avoid drinking too much of any fructose-containing beverages.

Metabolic syndrome is a blend of conditions including belly fat and insulin resistance that are associated with diabetes and cardiovascular disease.

PepsiCo, which funded Havel's research, did not think the results of the study were applicable to the company or the drinks the company manufactures. 

"This is a very interesting and important study," said a spokeswoman. "But it does not reflect a real-world situation nor is it applicable to PepsiCo since pure fructose is not an ingredient in any of our food and beverage products."

However, evidence showed HFCS does have a negative effect to say the least.

In another study, Havel and colleagues compared the immediate effects of consuming a meal with 25 percent of the energy from either HFCS, sucrose, fructose, or glucose. 

They found that blood triglyceride levels were raised to a similar level 24 hours after consuming fructose, sucrose, or HFCS, but not glucose, suggesting the fructose and fructose containing products may have the same effect on obesity and cardiovascular health.

The findings were published in the American Journal of Clinical Nutrition (vol 87 p 1194).

Nevertheless, long-term studies are needed to confirm whether the high levels of triglycerides produced by HFCS and sucrose have similar effects to fructose on abdominal fat and insulin resistance.

"It adds to what we have known for a long time," said Francine Kaufman at the Keck School of Medicine in Los Angeles. "It's probably not a good idea to consume too much sugar."

By David Liu, Ph.D., and edited by Heather Kelley.
Jun 25, 2008 - 4:43:07 PM