The use of diet pills by teenage girls has almost doubled in five years, according to University researchers.

The study, released Monday by the University’s Project EAT (Eating Among Teens), said the use of diet pills in high school-aged females went from 7.5 to 14.2 percent between 1999 to 2004.

University epidemiology professor Dianne Neumark-Sztainer conducted the study, which included 2,500 males and females.

“There was a high percentage of adolescents engaged in unhealthy weight control behavior,” Neumark-Sztainer said.

The use of diet pills often onset eating disorders and led to weight gain, she said.

Diet pills are not safe, said Ann Vosti, a family practitioner at Methodist Hospital’s Eating Disorder Institute.

“It’s not uncommon,” Vosti said. “I see it all the time.”

By 19 or 20 years old, 20 percent of the females in the study used diet pills.

Results from the study show that 21.9 percent of females use “very unhealthy weight control behaviors,” which include laxatives, vomiting, skipping meals or diet pills.

Males were “about half as likely to engage in unhealthy weight control behavior,” Neumark-Sztainer said.

The study showed that by the teenage years, physical activity in females drops to 3.93 hours per week, whereas males were active 6.11 hours per week.

Healthy weight loss is best obtained through exercise and nutrition, said Lisa Lemler, assistant director for programs at the recreational sports department.

“Basically, it comes down to balance between caloric intake, energy in and energy out,” she said.

Lemler agreed that diet pills are unhealthy.

Healthy weight loss can be achieved by eliminating 200 calories per day through a combination of nutrition and exercise, she said.

“One of the biggest problems with our society is not that we’re eating bad foods, but that we’re eating too much,” she said.

The surge behind diet pill use comes from intense marketing, Vosti said.

The only requirement for purchasing diet pills at General Nutrition Center is that the customer is at least 18 years old, said Jason Florin, manager of the Washington Avenue store.

Neumark-Sztainer said the results will be used to help teens feel better about their bodies and take care of themselves through lifestyle changes and physical activity.