DALLAS (AP) -- Adolescent girls who are depressed or try radical dieting like vomiting are more likely to become obese than those who eat high-fat foods or sometimes gorge themselves, a four-year study suggests.

Researchers said harsh weight-control methods -- including skipping meals and using laxatives -- can promote weight gain more than weight loss.

"A lot of these behaviors that adolescent girls are turning to are not effective in controlling obesity," said Eric Stice, research professor of psychology at the University of Texas at Austin.

One expert not involved in the study said the results were not surprising.

"We know that rigid dieting actually leads to one overeating or a change in metabolism," said Lisa Dorfman, a dietitian and psychotherapist who is a spokeswoman for the American Dietetic Association. "Your body slows down because it doesn't know when the next normal meal will come. Having a piece of cake is healthier than dieting for a week and having a (whole) cake."

The study, which looked at 496 Austin-area girls ages 11 to 15, was published in the April issue of the American Psychological Association's Journal of Consulting and Clinical Psychology.

Stice said that the message from the study is that young girls need to watch how many calories they eat and get exercise. "Don't swallow more calories than you need," he said.

While the study found that eating high-fat foods, binge-eating or infrequent exercise did not predict future obesity, Stice said that such effects are hard to measure accurately because youngsters may be reluctant to report eating high-fat foods and being sedentary.

The study found that another predictor of obesity was whether the girls' parents were obese - a connection that Stice said can be explained not only by genetics, but by environmental factors such as what's in the refrigerator.

As for the depression connection, while people who are depressed may overeat for comfort or distraction, the study said that it is also possible that a lack of the happy chemical serotonin - a condition often seen in depression -- also leads people to eat lots of carbohydrate-rich foods.

Candace Ayars of the Center for Health Research and Rural Advocacy at Geisinger Health Systems in Danville, Pa., said that it is important to remember that there are many other factors that could also lead to obesity.

"I wouldn't want people to think if they can't detect depression or eating disorders that they wouldn't become obese," Ayars said. "There are lots of explanations as to why we are obese that have nothing to do with depression or eating disorders."

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