Fructose May Affect Hunger Cues
Sugars in the Brain continued...
“When we eat, the body recognizes that food is coming in, and ultimately the brain is trying its best to regulate how many calories we need and how much fat we have in our bodies, and trying to maintain a balance so that we’re not overeating or under-eating,” Sherwin says.
Fructose seems to upset that balancing act, though researchers aren’t sure why.
One theory is that when humans evolved, the problem wasn’t overeating, but not getting enough calories. In that case, it wouldn’t have been a good idea for fructose, which is the primary sugar in fruit and fruit juices, to make us feel full since fruits may have been a primary food source.
That may have worked fine for cavemen, but it may not be so great for our sugar-saturated modern diets.
Advice to Dieters
So what does the study mean for health-conscious eaters?
That’s harder to say, says Jonathan Purnell, MD, an endocrinologist at Oregon Health & Science University in Portland. Purnell wrote an editorial on the study but was not involved in the research.
“This study didn’t prove that fructose causes weight gain,” Purnell says. “It doesn’t reflect real-world conditions.”
Industry representatives agree.
“When consumed together, as they almost always are, fructose and glucose balance each other out and would likely have no effect on normal hypothalamic blood flow,” says James Rippe, MD, professor of biomedical sciences at the University of Central Florida and a paid consultant for the Corn Refiners Association, the group that represents manufacturers of high-fructose corn syrup.
“Any suggestion that this artificial experiment has implications for human nutrition or obesity is unwarranted speculation,” says Rippe, in a statement prepared in response to the study.
Ideally, Purnell says, the next phase of studies would test the kinds of sugar mixtures found in foods, like table sugars and high-fructose corn syrup, against a comparison condition like water or an artificial sweetener.
“This study shouldn’t, all by itself, lead people to cut back on this food or that food,” Purnell says.
It would be a mistake, he says, to give up fruit, which has naturally occurring fructose.
“We don’t recommend limiting fruit intake. Although there’s fructose there, it’s also present with water and fiber that alter the characteristics of straight fructose alone. We think that doesn’t make fruit as much of a bad actor,” Purnell says.
What’s probably more practical, says Rachel Begun, RD, a spokeswoman for the American Academy of Nutrition and Dietetics, is to try to limit added sugars.
Americans take in nearly 150 pounds of added sugars per year, according to the U.S. Department of Agriculture, an amount that breaks down to nearly 28 teaspoons or 440 calories every day.
“It's safe to say that Americans are consuming too much sugar in all forms and we need to significantly reduce our intake," says Begun, who wasn’t involved in the research.