“It’s not any one source of calories - it’s calories in general,” Sievenpiper said.
One theory has been that because of the way fructose is processed in the liver, people who eat a lot of it may be more likely to become insulin-resistant than those who choose other carbs. The research team didn’t look at individuals’ insulin levels, so the new analysis doesn’t say anything about the effects of fructose on the blood sugar-regulating hormone, according to Sievenpiper.
It also doesn’t show how weight was distributed in people who ate extra fructose. Dr. Frank Hu, a nutrition researcher at the Harvard School of Public Health in Cambridge, Massachusetts, said that fructose may increase fat around the belly and organs more than glucose, for example.
That type of fat has been linked to heart disease and diabetes.
A study from Princeton published in the February issue of the journal Pharmacology, Biochemistry and Behavior (PDF) shows that high fructose corn syrup (HFCS), used as a cheap sweetener in everything from Coke to Progresso soup, is not the same as table sugar, namely for the way that it makes you gain 48% more weight.
We wrote about this a year ago, after the study was first completed.
Over 6 months, one group of rats was fed rat chow sweetened with HFCS and another just regular rat chow. The group consuming HFCS showed signed of obesity, like unusual weight gain, and big increases in triglycerides and fat deposits in the belly. Overall they rats on HFCS gained 48% more weight than those on a regular diet.
In an earlier study, the researchers gave one group of rats access to water sweetened with table sugar and another, water sweetened with HFCS. The rats on HFCS gained much more weight than the others. The concentration in the table sugar formula was the same as what is found in some soft drinks, while the HFCS was only half as concentrated as most soda pops.
“In terms of body weight, it looks like the same amount of fructose or glucose would have the same effects,” Hu, who wasn’t involved in the study, told Reuters Health.
“But the other metabolic effects can be different,” he said.
“We have to look beyond just body weight when we talk about the effects of different sugars.”
Because most of the studies they analyzed were small and didn’t follow dieters for very long, the researchers said that people shouldn’t base their own nutrition decisions on the new findings.
There’s also a need for larger studies to compare the effects of natural fructose, like the kind in fruits and vegetables, with the kind of sugar added to other food and drinks in amounts most people get in a typical day, Sievenpiper said.
In a meta-analysis that promises to generate a spectacular debate, Canadian researchers have challenged what they call “the fructose-centered view of obesity” with the finding that fructose does not cause weight gain in the setting of a calorie-controlled diet.
The results were reported here at the International Diabetes Federation World Diabetes Congress 2011 by John Sievenpiper, MD, PhD, from McMaster University in Hamilton, Ontario, and his colleagues.
In presenting the findings, Dr. Sievenpiper added fuel to the fructose debate, which has already sparked inflammatory headlines, lively letters to journal editors, and impassioned YouTube lectures that have gone viral, elevating some of his opponents to almost “rock star status,” he said.
Richard Johnson, MD, professor of medicine at the University of Colorado, Denver, and author of The Sugar Fix: The High-Fructose Fallout That Is Making You Fat and Sick, said he has concerns about the Canadian findings.
“The way fructose stimulates weight is by causing leptin resistance; hence, it will not be observed with short-term studies or with isocaloric diets. Understanding physiology is required,” he told Medscape Medical News.
The researchers report receiving grants from Coca-Cola, but said the company was otherwise not involved in the current study. The primary funding source for the report was the Canadian Institutes of Health Research.
John L. Sievenpiper,
Russell J. de Souza,
Matthew E. Yu,
Amanda J. Carleton,
Marco Di Buono,
Alexandra L. Jenkins,
Lawrence A. Leiter,
Thomas M.S. Wolever,
Cyril W.C. Kendall,
and David J.A. Jenkins
Ann Intern Med February 21, 2012 156:291-304;