Here’s the good news: More teenagers, especially girls, are trying to lose weight. But at least one of the methods some are using to shed pounds is concerning to pediatricians.

Results from the National Health and Nutrition Examination Survey show nearly 40% of adolescents said they had tried to lose weight during the past year. That’s up from less than 25% in the previous survey. Of those teens, nearly half were girls, and a third were boys.

The survey of more than 1,200 boys and girls ages 16 to 19 included physical exams in mobile health units and in-home interviews. More than half of the Hispanic teens in the survey said they tried to lose weight while about a third of non-Hispanic black, non-Hispanic white and Asian teens reported they tried to drop some pounds.

Experts reviewing the results were pleased to see the teens, for the most part, were using healthy strategies to slim down. More than half the teens said they drank a lot more water and, 85% said they exercised more. About half said they changed their diets to include more fruits and vegetables and less junk food.

However, a significant number of the teens said they skipped meals, which the American Academy of Pediatrics says is unhealthy. And some physicians were concerned about the motivation of the teens. Were they aiming to be healthier or trying to change their appearance? If it’s about body image, the teens could resort to more extreme methods that could have adverse consequences.

The survey authors hope clinicians use the results to better counsel their young patients on how to build a strong foundation for a healthy life.