For young women concerned about their diet and weight, a bout of unhealthy eating when in a bad mood can make you feel a lot worse about yourself, according to a new US study.

Penn State researchers recruited 131 women who regularly consumed junk food but also had concerns about body image, but at the same time didn't have eating disorders. The research team gave each subject a handheld computer, which prompted the subjects several times a day to answer questions about their mood and eating behaviors.

What we know about mood and eating behaviors comes primarily from studies with eating disorder patients or from laboratory studies," says research associate Kristin Heron. "We were interested in studying women in their everyday lives to see whether mood changed before or after they engaged in unhealthy eating and weight control behaviors."

The researchers noted that for women who were in a bad or negative mood before eating junk food, their moods worsened significantly after the indiscretion. But when women were in a good mood before eating junk food, their moods remained the same after eating unhealthy food.

"There was little in the way of mood changes right before the unhealthy eating behaviors," she says. "However, negative mood was significantly higher after these behaviors."

Heron presented the findings this weekend at the American Psychosomatic Society conference in Miami, Florida.