Obese women more impulsive

Nov 11 2008

According to the latest research obese women are more impulsive than other females but this does not apply to obese men.

The new study found that obese women display significantly weaker impulse control than normal-weight women, but between obese and normal-weight men, the impulsivity levels are nearly the same.

The study by researchers at the University of Alabama, Birmingham aimed to find out how obese and normal-weight men and women differed in their decision-making skills, specifically in delay discounting, which is a measure of how much an individual is driven by immediate gratification as against the willingness to wait for delayed but greater rewards.

The researchers from the Department of Psychology involved 95 men and women in the study and gave them the choice of receiving varying hypothetical amounts of money immediately or fixed hypothetical amounts of money to be received after delays of two weeks, one month, six months or one, three, five or 10 years.

These hypothetical rewards ranged from $1,000 to $50,000 and the researchers found that obese women discounted the value of future rewards at a rate three-to-four times greater than that of normal-weight women, suggesting greater impulsivity.

Obese men and the male and female control subjects however, all showed similar levels of delay discounting and the results remained the same, even when differences in IQ and income, both of which have been found to be related to measures of impulsivity, were accounted for.

Dr. Rosalyn Weller, the study's principle investigator, says a possible explanation for the differences between men and women may be found in a personality trait known as eating-related disinhibition, which is the tendency to overeat in response to certain situations or cues such as a big display of dessert.

Dr. Weller says previous studies have shown that those who score higher in disinhibition have higher body mass indexes and gain weight more easily, but men score lower in disinhibition than women.

Dr. Weller says the study found that obese men have more impulse control than obese women and may be protected from more impulsive behavior on the delay-discounting task by having lower disinhibition in general, while obese women have the double whammy of being female and having higher body mass index.

The UAB researchers are now conducting delay-discounting studies using functional brain imaging (fMRI) to investigate what happens in the brains of obese individuals who vary in impulsivity as they make decisions.

The study is published in the November issue of the journal Appetite.