May 14, 2009

Study Shows Brain May Sabotage Weight-Loss Efforts

According to a report in the health journal Obesity, scientists examining the efficacy of public health campaigns against obesity have discovered that such programs may result in the opposite of the intended effect.

The research shows that public service announcements designed to encourage over-eaters to abstain from sweet and fatty foods and get more exercise may actually inspire people to indulge even more.

In a study conducted at the University of Illinois, scientists asked 53 college students to evaluate a series of motivational posters designed to promote exercise.  After rating the posters, the students were then given a container of raisins and asked to judge the quality of the raisins, being told that they could eat as many as they needed to make a proper evaluation.

Researchers then conducted the experiment again, this time substituting the exercise endorsements for another set of posters promoting things like team-work and activist groups.  As with the first group, the subjects were then asked to rate raisins and told to eat as many as needed.

The researchers observed that those students who had analyzed the posters promoting exercise consumed significantly more raisings before making their evaluations than those in the control group.

Delores Alberracin, a professor of psychiatry and lead author of the study, believes that the posters encouraging exercise may have simply inspired the subjects to do something "“ though not necessarily exercise.  As food was then made available, eating then became something to do.

The significance of this study for public health projects, Albarracin suggests, is that we need to be more cautious about when and where we try to motivate people to work out.  For example, she said, commercials intended to encourage people to activity may not be effective when people are sitting in front of a television with a pantry full of snacks in the kitchen.

Dr. Louis Aronne, clinical professor of medicine and director of the Comprehensive Weight Control Program at New York-Presbyterian Hospital, says that the study highlights the controversial possibility that public health campaigns may cause more harm than good if not targeted correctly.

The Psychology Of Flavor

In a similar vein, another study conducted at the Oregon Research Institute has demonstrated that low-fat and low-calorie labels on food products may also have unintended results.

In their study, young women were asked to drink a chocolate milkshake while being run through brain imaging device.  Half of the subjects were told that the drink was a regular milk shake and the other half that it was a low-fat imitation.  Both groups, however, were given the same full-fat, full-sugar chocolate concoction.

The images of the scans produced from the women who knew they were drinking a real milk shake showed that their brains' reward centers lit up with activity as they consumed the drink.  For the group of women who believed they were getting a low-fat version of the shake, however, researchers observed significantly less activity in the pleasure-sensing regions of the brain.

As the group's senior researcher Eric Stice pointed out, "knowing" that the rich and creamy drink was low-fat seemed to remove much of the pleasure from the experience.

"It's really interesting when you think of this enterprise of the food industry to come up with lower-calorie alternatives," mused Stice.  "This study shows that it may not be such a good idea to have all those low-fat alternatives since people may be experiencing less of a sense of reward when they eat "“ and that would make these low-calorie foods completely useless."

In a separate study published in the International Journal of Eating Disorders, Stice's group examined the brain chemistry of "emotional eaters" "“ people who eat in response to feelings of sadness or depression "“ and compared it to those of non-emotional eaters.

As they suspected, emotional eaters showed a higher level of activity in their brains' reward centers in response to eating than that observed in the control group.

According to Dr. David Heber of the Center for Human Nutrition at UCLA, this influx of research is helping scientists and health experts to stitch together a more complete picture of the brain chemistry at work in over-eating, all of which will be necessary in the development of medications to help obese people lose weight.

Until such medications are developed, says Madelyn Fernstrom of the Weight Management Center at the University of Pittsburgh, people need to remain very conscientious about their calorie intake and in understanding how their brains may be working to counter their weight loss efforts.

"We need to get a better understanding of the complex interaction between behavior and biology and to recognize that most of the time we're not eating because we have physical hunger," she says.


On The Net:

journal Obesity


University of Illinois