Researchers say they've found more evidence of a link between a rapid rise in obesity and a corn product used to sweeten soft drinks and food since the 1970s.
The researchers examined consumption records from the U.S. Department of Agriculture for 1967-2000 and combined it with previous research and their own analyses.
The data showed an increase in the use of high-fructose corn sweeteners in the late 1970s and 1980s "coincidental with the epidemic of obesity,'' said one of the researchers, Dr. George A. Bray, a longtime obesity scientist with Louisiana State University System's Pennington Biomedical Research Center.
He noted the research didn't prove a definitive link.
"Body weights rose slowly for most of the 20th century until the late 1980s,'' Bray said. "At that time, many countries showed a sudden increase in the rate at which obesity has been galloping forward.''
The study is being published in the April issue of the American Journal of Clinical Nutrition. But spokesmen with the food and beverage industry and a leading critic of fast food both said weight gain would be a problem even if the sweetener didn't exist.
"It's not about the high-fructose corn syrup being a part of foods, it's about how many calories we're eating against how many calories we're burning,'' said Alison Kretser, a registered dietitian and director of scientific and nutrition policy for the Grocery Manufacturers of America.
Its members include The Coca-Cola Co., Kellogg Co. and Sara Lee Corp.
Obesity among American adults climbed from 23 percent in the early 1990s to 30 percent today, according to the U.S. Department of Health and Human Services. And two-thirds of Americans are overweight. That means increased risks for heart disease, diabetes and certain cancers.
The debate over high-fructose sweeteners centers on how the body processes sugar. Unlike glucose, a major component in table sugar, fructose doesn't trigger responses in hormones that regulate energy use and appetite. That means fructose is more likely to be converted into fat, the researchers said.
The sweeteners are also cheaper to produce and use in food manufacturing than cane and beet sugars, the study noted.
The report, which says more study is needed, also lays blame on people for eating more and exercising less.
Kretser said studies on how the body digests the fructose corn sweetener are inconclusive because they were done on animals.
Companies are responding to the rise in obesity by adding more nutritious sweeteners to products, such as diet sodas, and returning to smaller containers, she said.
Barry M. Popkin, a professor of nutrition at the University of North Carolina at Chapel Hill who worked on the study, said he believes a third to half of the increase in calorie intake since the 1970s comes from soft drinks and fruit drinks. Their report says more than 132 calories a day consumed by Americans age 2 and older come from corn sweeteners.
"We cannot increase our physical activity enough to offset the extra 200 calories a day Americans are consuming,'' he said.
Michael Jacobson, executive director of the Center for Science in the Public Interest, a consumer advocacy group, said there's no nutritional difference in the soft drinks sweetened with table sugar, or sucrose, decades ago and those sold today with high-fructose corn sweeteners.
He said either blend would contribute to a fat problem because of the increase in container sizes and the mass distribution of soft drinks.
Jacobson, a microbiologist and leading critic of the food industry, also called the study erroneous.
"The authors of this paper misunderstand chemistry, draw erroneous conclusions and have done a disservice to the public in generating this controversy,'' he said.