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Brain Imaging Study Supports Notion of Food Addiction
The study of high-glycemic index foods by researchers at Boston Children’s Hospital investigated how eating is regulated by the dopamine-containing pleasure centers of the brain.
“Beyond reward and craving, this part of the brain is also linked to substance abuse and dependence, which raises the question as to whether certain foods might be addictive,” said David Ludwig, MD, PhD, and director of the New Balance Foundation Obesity Prevention Center.
To examine the link, researchers measured blood glucose levels and hunger. They also used functional magnetic resonance imaging (MRI) to observe brain activity in the four hours after a meal, a time period, they say, that influences eating behavior at the next meal.
The researchers recruited 12 overweight or obese men for the study. They had them eat two test meals made up of milkshakes that had the same calories, taste and sweetness.
While the two milkshakes were essentially the same, one contained rapidly digesting — or high-glycemic index — carbohydrates, while the other was made up of slowly digesting (or low-glycemic index) carbohydrates.
The researchers found that after the men drank the high-glycemic index milkshake, they experienced an initial surge in blood sugar levels, followed by sharp crash four hours later.
This decrease in blood glucose was associated with excessive hunger and intense activation of the nucleus accumbens, a critical brain region involved in addictive behaviors, according to the researchers.
“These findings suggest that limiting high-glycemic index carbohydrates like white bread and potatoes could help obese individuals reduce cravings and control the urge to overeat,” said Ludwig.
He acknowledges that the concept of food addiction remains provocative, noting that the findings from the new study suggest that more interventional and observational studies be done.
The study was published in the American Journal of Clinical Nutrition.
Source: Boston Children’s Hospital
Brain Imaging Study photo by shutterstock.
Why Do We Punish the Most Generous in a Group?
Researchers at Baylor University note this highlights the importance of conforming to the standards of a group, pointing out that freeloaders — those who were stingiest — also were ostracized by the group.
Published in the journal Social Science Research, the study also showed that besides socially rejecting especially generous or stingy givers, other group members “paid” to punish them through a points system.
“This is puzzling behavior,” said Kyle Irwin, Ph.D., an assistant professor of sociology at Baylor University.
“Why would you punish the people who are doing the most — especially when it benefits the group? It doesn’t seem to make sense on the surface, but it shows the power of norms. It may be that group members think it’s more important to conform than for the group to do well.”
For the study, Irwin and his co-researcher, Christine Horne, Ph.D., a sociologist at Washington State University, conducted a “public goods” experiment with 310 participants.
Each person was given 100 points and had to decide how many to give to the group and how many to keep. Contributions were divided equally regardless of how much people donated.
Decisions were made via computers, and for each participant, the other “group members” actually were simulated, with pre-programmed behavior, the researchers explained.
Each participant was told that he or she would see the amounts of four others and be the fifth giver, with a sixth person ending the sequence. The final giver always was pre-programmed to be stingier or much more generous than the others.
Group members’ donations averaged 50 percent of their points. The stingiest individual gave only 10 percent, while the most generous gave 90 percent.
Each group member also had the opportunity to “pay” via the points system to punish those who contributed the most. The “punisher” would have to give up one point for every three points he or she deducted from the most generous member, according to the researchers.
Finally, each person was asked to rate on a scale of 1 to 9 how much they wanted each of the others to remain in the group.
Irwin likened the punishments to shunning or poking fun at someone who had done the bulk of work in a group project for a class — or even kicking that person out of the group.
“There could be a number of reasons why the others punish a generous member,” he said. “It may be that the generous giver made them look or feel bad. Or they may feel jealous or like they’re not doing enough.”
He added that at some point, if the contributions became very large, the desire of the group members to benefit from the most generous person’s largesse may override their desire to punish that person.
Source: Baylor University
Hands with various amounts of money photo by shutterstock.
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