We all know that too much sugar is not good for us, but researchers from the US have discovered that drinks sweetened with fructose as opposed to glucose were significantly more likely to increase insulin resistance and belly fat in obese and overweight people, leading to medical conditions that increased their risk of heart attack and stroke.

The study was the work of Dr Peter Havel, a researcher in the Department of Nutrition at the University of California at Davis, and colleagues, and was published in the April 20 issue of the Journal of Clinical Investigation.

Over the twelve months of 2005, the average American consumed about 64 kg of extra sugar from drinking sweetened soft drinks: this is approximately the weight of an average height, slim American woman.

But although studies in animals have shown that compared with glucose, dietary fructose leads to increased insulin resistance plus higher levels of blood cholesterol and fats, there has been little equivalent research on humans.

Over the 10 weeks of the study, Havel and colleagues showed that human consumption of beverages sweetened with fructose but not glucose can worsen the body’s sensitivity to insulin and how it handles fat.

For the study, which involved 32 overweight and obese men and women aged around 50, the participants spent 2 weeks in a closely observed inpatient setting and then 8 weeks in an outpatient setting. Over the two phases they drank beverages sweetened with glucose (15 subjects) or fructose (17 subjects) comprising 25 per cent of their daily calorie intake.

During the 10 weeks in total of the study, participants in both groups put on about the same amount of weight, but only those in the fructose group showed an increase in belly fat.

Also, only the participants in the fructose group became less sensitive to insulin (the hormone that controls how much glucose is in the bloodstream), and developed higher levels of total and LDL or “bad” cholesterol.

The fructose group also showed higher levels of hepatic DNL (de novo lipogenesis, fat that is produced from excess digested carbohydrate) and other signs that their bodies were producing fat differently to the glucose group.

The researchers concluded that:

“These data suggest that dietary fructose specifically increases DNL, promotes dyslipidemia, decreases insulin sensitivity, and increases visceral adiposity in overweight/obese adults.”

Commenting in the same issue of the journal, Susanna Hofmann and Matthias Tschöp said that while these symptoms are telltale signs of metabolic syndrome, which raises a person’s risk of heart attack, we still don’t know what the long term implications of fructose consumption on such a risk might be.

“Consuming fructose-sweetened, not glucose-sweetened, beverages increases visceral adiposity and lipids and decreases insulin sensitivity in overweight/obese humans.”
Kimber L. Stanhope, Jean Marc Schwarz, Nancy L. Keim, Steven C. Griffen, Andrew A. Bremer, James L. Graham, Bonnie Hatcher, Chad L. Cox, Artem Dyachenko, Wei Zhang, John P. McGahan, Anthony Seibert, Ronald M. Krauss, Sally Chiu, Ernst J. Schaefer, Masumi Ai, Seiko Otokozawa, Katsuyuki Nakajima, Takamitsu Nakano, Carine Beysen, Marc K. Hellerstein, Lars Berglund, Peter J. Havel.
J. Clin. Invest. , Published April 20, 2009.

Sources: Journal of Clinical Investigation.

Written by: Catharine Paddock, PhD