While it would seem like just eating too much and not exercising enough are the tickets to obesity, many behavioral and genetic factors actually figure into the obesity equation, although in ways that are not yet fully understood. A team of psychology researchers in Austin followed adolescent girls to see who was most likely to develop a serious weight problem.

What the researchers wanted to know: What behavioral and psychological factors predict which girls will become obese?

What they did: About 500 girls ages 11 to 15 joined the study. They were weighed and measured when they joined, and then once a year for the next four years. Research assistants interviewed the girls about the amount of fat they consumed, whether they binged on food, their exercise patterns, dieting, dangerous dieting (vomiting, laxative abuse, and diuretic abuse), depressive symptoms, and whether their parents were obese. Eight percent of the girls were obese when they joined the study, and another 3 percent became obese over the course of the study.

What they found: Girls who dieted, had overweight parents, had symptoms of depression, or used vomiting, laxatives, or diuretics to lose weight were more likely to become obese during the four years they were enrolled in the study. Interestingly, eating high-fat foods, bingeing on food, and not getting much exercise didn't have a statistically significant effect on the likelihood of becoming obese.

What the study means to you: Although at a first glance it could appear that the study shows that dieting increases teenage girls' risk of obesity, it is more likely that many girls who are at risk of obesity don't know how to control their weight effectively and so pack on the pounds. This suggests that many teens could benefit from efforts to teach them about weight-control strategies. It also lines up with the results of several other studies finding that obesity tends to run in families and that depression increases the risk of obesity, perhaps because people eat for comfort.

Caveats: This is a relatively small study; although 496 girls were involved, only 15 became obese during the study. Also, the long-term impact of other behaviors, like eating fatty foods and binge eating, may not have shown up in the study.

Find out more: The American Academy of Pediatrics has a web page on obesity, including links to information about nutrition and exercise.

Read the article: Stice, E., et al. "Physiological and Behavioral Risk Factors for Obesity Onset in Adolescent Girls: A Prospective Study." Journal of Consulting and Clinical Psychology. April 2005, Vol. 73, No. 2, pp. 195-202.

Abstract online: http://content.apa.org