Study finds that obese women are more impulsive than other females

Hannah K. Webber, Staff Writer
Published On: 12/ 2/2008

Obese women are found to have a more feeble impulse control than normal weight women, are more likely to want instant gratification.

Researchers at UAB conducted a study that found obese women displaying weaker impulse control than normal-weight women. The study also found that impulsivity levels are nearly the same between obese and normal-weight men.

A UAB Media Relations article by Gail Short states that the study was conducted to see how obese and normal-weight men and women differed in their decision-making skills. The study focused on delay discounting, which is the measure of how much an individual is driven by immediate gratification versus the willingness to wait for delayed but greater rewards.

Why did UAB researchers decide to focus on impulse control and obesity?

Kathy Avsar, a UAB psychology graduate student and co-author of the study, cited the connection between obesity and heart disease.

“Understanding mechanisms that might lead to obesity is the first step in developing effective treatments for obesity,” she said. “Several similarities are seen between drug addiction and obesity such as both being driven by cues in the environment. Research had shown in drug addiction that impulsivity was a risk factor and we thought that it might be a risk factor in some individuals who develop obesity.”

The study began with a screening process. According to Rosalyn Weller, Ph.D., the study’s principle investigator, participants for the study were recruited from introductory psychology classes by way of a screening questionnaire, followed by a phone interview. The researchers needed people who were obese – defined by a body mass index (BMI) of more than 30 – and people who were of normal-weight – with a BMI between 18.5 and 24.9.

“We used a delay-discounting task where individuals were given a choice between two amounts of money, a smaller amount that was immediately available and a larger amount that would be available after a specified number of days,” Avsar said. “We believe that individuals who are more impulsive, more often want the money that is available now. They are unable or unwilling to wait for the larger amount.”

“We ended up with useful data from 26 obese women, 29 normal-weight women, 21 obese men, and 19 normal-weight men,” Weller added.

The results of the study, according to Avsar, were that overweight women are more likely to want the immediate reward. When those women have to wait, the amount of money would have to be larger than that found in the studies of normal-weight women.

“No such differences were found for obese vs. normal-weight men, and in fact, the control women, control men, and obese men all showed similar delay discounting,” Weller said. “The results were the same when we statistically controlled for obese versus control group differences in IQ and income.”

Weller said that she and her fellow investigators were surprised by the fact that the differences in impulsivity between obese and normal-weight women were not found in men. She believes a possible explanation for this lies in a particular personality trait, eating-related disinhibition, or the tendency to overeat in response to situations or cues such a big display of desserts. In general, men score lower on this trait than women, and those with lower BMIs score lower than those with higher BMIs, so obese women may have higher levels of this trait.

Email: hwebber@uab.edu