WEDNESDAY, July 20 (HealthDay News) -- Personality traits may play key roles in body weight, according to a new U.S. study.

Researchers from the U.S. National Institute on Aging found that people who are impulsive, cynical, competitive or aggressive were more likely to be overweight. And those who are highly neurotic and less conscientious are likely to see their weight go through many ups and downs.

"Individuals with this constellation of traits tend to give in to temptation and lack the discipline to stay on track amid difficulties or frustration," said the researchers in an institute news release. "To maintain a healthy weight, it is typically necessary to have a healthy diet and a sustained program of physical activity, both of which require commitment and restraint. Such control may be difficult for highly impulsive individuals."

For the study, published online July 11 in the American Psychological Association's Journal of Personality and Social Psychology, the researchers examined data compiled over 50 years on nearly 2,000 generally healthy and highly educated people to determine how their personalities might affect their weight and body mass index.

The participants were assessed on the so-called "big five" personality traits -- openness, conscientiousness, extraversion, agreeableness and neuroticism -- as well as 30 subcategories of these traits. They were also weighed and measured over the course of the study.

Although people tend to gain weight as they age, the study found those who are impulsive were the most likely to be overweight. People who scored in the top 10 percent on impulsivity weighed an average of 22 pounds more than those in the bottom 10 percent, the researchers said.

"Previous research has found that impulsive individuals are prone to binge eating and alcohol consumption," the study's author, Angelina R. Sutin, said in the news release. "These behavioral patterns may contribute to weight gain over time."

Those who are risk takers, antagonistic, cynical, competitive and aggressive also had greater weight gain, the study showed.

On the flip side, the study found that conscientious people are typically thinner and their weight did not trigger changes in personality during adulthood.

"The pathway from personality traits to weight gain is complex and probably includes physiological mechanisms, in addition to behavioral ones," Sutin concluded. "We hope that by more clearly identifying the association between personality and obesity, more tailored treatments will be developed. For example, lifestyle and exercise interventions that are done in a group setting may be more effective for extroverts than for introverts."

More information

The U.S. National Heart, Lung, and Blood Institute has more on controlling your weight.