Obese children may be more susceptible to food advertising than healthy-weight children, a new study finds, suggesting that such advertisements may play a bigger role in the childhood obesity epidemic than once thought.
When shown TV food commercials, the brains of overweight and obese teenagers were found to be overstimulated in the regions that control pleasure, taste and — most surprisingly — the mouth, suggesting they actually mentally simulated unhealthy eating habits. The findings, published in the journal Cerebral Cortex, suggest that such habits may make it difficult to lose weight later in life, and that dieting efforts should not only target the initial desire to eat tempting food, but the subsequent thinking about actually tasting and eating it.
In the past thirty years, the obesity rate has more than doubled in children and quadrupled in adolescents, according to the Centers for Disease Control and Prevention. At the same time, the prevalence of food advertising has increased dramatically, and research has linked the number of television shows viewed during childhood with greater risk for obesity. In particular, considerable evidence suggests that exposure to food marketing promotes eating habits that contribute to obesity. For example, a 2013 study found that children who regularly watched television commercials consumed more junk food, and had a distorted view of healthy portion sizes and choices, than households where commercial-free television was viewed, while other studies have demonstrated a significant increase in caloric intake after exposure to food advertising.
In this latest study, researchers at Dartmouth University used functional magnetic resonance imaging (fMRI) to examine brain responses to two dozen fast food commercials and non-food commercials in a group of overweight/obese and healthy-weight adolescents ages 12-16. The commercials were embedded within an age-appropriate show, “The Big Bang Theory,” so the participants were unaware of the study’s purpose.
The results show that in all the adolescents, the brain regions involved in attention and focus (occipital lobe, precuneus, superior temporal gyri and right insula) and in processing rewards (nucleus accumbens and orbitofrontal cortex) were more strongly active while viewing food commercials than non-food commercials. Notably, adolescents with higher body fat showed greater reward-related activity than healthy weight teens in the orbitofrontal cortex and in regions associated with taste perception, indicating heightened alertness and reactivity to food-related cues. The most surprising finding, said the researchers, was that the food commercials also activated the overweight adolescents’ brains in the region that controls their mouths. This region is part of the larger sensory system that is important for observational learning. Their brains were, apparently, priming the overweight/obese children to consume junk food.
“This finding suggests the intriguing possibility that overweight and obese adolescents mentally simulate eating while watching food commercials,” said lead author Kristina Rapuano, a graduate student in Dartmouth’s Brain Imaging Lab. “These brain responses may demonstrate one factor whereby unhealthy eating behaviors become reinforced and turned into habits that potentially hamper a person’s ability lose weight later in life.”
Although previous studies have shown heightened brain reward responses to viewing appetizing food in general, the Dartmouth study is one of the first to extend this relationship to real world food cues — for example, TV commercials for McDonald’s and Burger King — that adolescents encounter regularly. The brain’s reward circuitry involves the release of dopamine and other neurotransmitter chemicals that give pleasure and may lead to addictive behavior. While often associated with drug addiction, recent research has demonstrated that the reward cycle in the brain may also play an important role in obesity.
Currently, food and beverage companies in the United States spend more than $10 billion annually on marketing their wares to American children. Each day, children and adolescents see an average of 17-21 food advertisements. It isn’t surprising, then, that they show a strong reward response to food commercials. But the new findings show that these heightened reward responses are coupled with bodily movements that indicate simulated eating — offering a clue into a potential mechanism on how unhealthy eating habits are developed.
“Unhealthy eating is thought to involve both an initial desire to eat a tempting food, such as a piece of cake, and a motor plan to enact the behavior, or eating it,” Rapuano said. “Diet intervention strategies largely focus on minimizing or inhibiting the desire to eat the tempting food, with the logic being that if one does not desire, then one won’t enact. Our findings suggest a second point of intervention may be the somatomotor simulation of eating behavior that follows from the desire to eat. Interventions that target this system, either to minimize the simulation of unhealthy eating or to promote the simulation of healthy eating, may ultimately prove to be more useful than trying to suppress the desire to eat.”
Another good strategy? Reducing screen time. Research indicates that children who watch more than three hours of television a day are 50 percent more likely to be obese than children who watch fewer than two hours. And there’s evidence that early TV habits may have long-lasting effects: Studies following children from birth have found that TV viewing in childhood predicts obesity risk well into adulthood and mid-life.