It’s a beautiful sunny day and you’re walking down the boardwalk with your loved one in hand listening to a story he or she is telling you. Everything is going well until you pass by food stands and the smell of hotdogs, crêpes, and sausages distractingly swirl in front of your nose, abruptly making it difficult to follow the story. This problem is only unique to obese women, a new study finds, and the discovery may help change the future of unhealthy eating patterns.
Researchers from Yale University tested the strength food has over learning for both obese men and women, and published their findings in the journal Current Biology. What they found through examining 133 normal-weight and obese-weight men and women is that they learn associations between cues and rewards. Only one group seemed to be so distracted by food that they struggled with the task, and that group was explicitly obese women.
"Our study shows that obesity may involve a specific impairment not in the processing of food itself, but rather in how obese individuals — or at least obese women — learn about cues in the environment that predict food," lead author Ifat Levy, assistant professor of comparative medicine and neurobiology at Yale School of Medicine, said in a press release.
In order to properly test the ability of normal-weight and obese-weigh men and women, the researchers presented the participants with one of two different colored squares followed by a reward. The reward was either an image of a food or money, and participants were told they would receive all the rewards they saw during the experiment. Afterward, researchers held up different color squares and asked the participants to rate on a scale of one to nine how likely it was that a specific reward image would appear.
"Instead of focusing on reactions to the food itself, our results call for shifting attention to the way obese individuals learn about the environment and how they approach or ignore cues associated with food," the researchers wrote in the study. "Rather than target these individuals' behavior with food, we suggest that a successful intervention should aim to modify their interactions with other cues that determine their eating patterns."
What the researchers observed was not a learning impairment but instead a food-specific impairment found only in obese female participants. There were 18 obese women who had a difficult time learning and modifying links to which color associated with which reward. They rated both squares as highly predictive of a food reward and couldn’t adjust their cues when switched for the next set of tests. Meanwhile, 16 obese women had no problem associating color to reward when the reward was with money, and performed similarly to normal-weight women. Researchers were surprised to find no distinguishable difference between the cue-reward performance of normal and obese-weight participants.
The food reward was switched from M&M chocolates to pretzels because, according to researchers, “women tend to like and crave chocolate more than men.” It made no difference though, women were just as susceptible to being distracted by food whether it was the M&Ms or the pretzels. "This is not a general learning impairment, as obese women had no problem [learning] when the reward was money rather than food. An intriguing possibility is that, by modifying flawed associations between food and environmental cues, we may be able to change eating patterns," Levy said.
With more than one-third of the United States adult population weighing in as obese, finding a way to change eating patterns to healthier ones by using cue-reward associations or other learning tasks is essential. Obesity brings with it the treat of heart disease, stroke, type 2 diabetes, and certain types of cancers among other life-threatening health conditions, according to the Centers for Disease Control and Prevention.
Researchers conclude that future research is necessary in order to understand what is going on in the body on a chemical, hormonal, and neurological level. When the study was performed with obese and normal-weight rats, the learning problems were caused by changes in the brain, specifically the hippocampus, which is responsible for memory and the prefrontal cortex, which controls impulse and self-restraint.
Source: Zhang Z, Manson KF, Schiller D, and Levy I. Impaired associative learning with food rewards in obese women. Current Biology. 2014.