There's a new factor in the diet and obesity equation that bears consideration.
Part of the equation is simple: if you eat high-calorie foods, you're more likely to add extra weight. But new evidence suggests - perhaps not conclusively, but persuasively - that one high-calorie staple of our modern diet may actually encourage overeating.
Scientists have used magnetic resonance imaging to study the effects of the sugar fructose on the human brain. Their findings show fructose can trigger brain changes that may lead to overeating. This small study stops short of claiming that fructose - commonly used in the high-fructose corn syrup sweetening many processed foods and beverages - can cause obesity. But experts say it suggests these sweeteners pose special risks.
The study determined that after a person drinks a fructose beverage, the subject's brain doesn't register the same feeling of being full as when simple glucose sugar is consumed.
Researchers used MRI scans to track blood flow in the brains of 20 subjects before and after they had drinks containing glucose or fructose. Scans showed that drinking glucose suppressed the activity of areas of the brain that register reward and desire for food. Fructose didn't. As a result, researchers think the desire to eat continues despite the consumption of fructose.
There's circumstantial evidence as well. Consumption of fructose has risen dramatically since the 1970s - and, perhaps not coincidentally, so has obesity. A third of U.S. children and teens and more than two-thirds of adults are now classified as obese or overweight.
Many in the food industry would dispute the study's conclusion and argue that the risk of fructose-based sweeteners is no higher than for other sweeteners. But that begs the question - shouldn't most of us be consuming less sugar in all its forms? Certainly, most doctors agree that typical American diet probably contains too much refined sugar.
Some pressure is building for a ban on high-fructose corn syrup. One Facebook page promoting the ban has upwards of 200,000 "likes." But we're not in favor of bans on products which aren't innately harmful - we don't think the government needs to play the role of a nanny or dietician for the public. We think informed citizens will make the right health decisions for themselves.
We're sure there will be more studies of the health effects of fructose. In the meantime, it's undoubtedly a good idea to avoid any refined sugars whenever possible.