Freshmen at Florida's Lakewood High School lined up against gold and black gymnasium mats on Friday to have their height and weight measured, an assessment to launch a novel study on fighting teenage obesity with trendy new technology.

Researchers affiliated with Johns Hopkins Medicine, whose network includes a Florida children's hospital near the school, plan to use results of the screening to select about 50 overweight students and track their activity levels using the Fitbit, a connected wristband.

Wearable technology, expected to take off next year when Apple Inc introduces its health-oriented Apple Watch, has shown mixed promise in research. Yet medical literature has little to say about the effectiveness in adolescents, whose obesity rates have quadrupled in the last 30 years, with nearly one in five now being obese, according the U.S. Centers for Disease Control and Prevention.

"It's cool. You can wear it and it measures your activity," said Dr. Raquel Hernandez, lead researcher and an assistant professor of pediatrics at John Hopkins Medical School, who works at All Children's Hospital in St. Petersburg, Florida.

"It also can help the student know what they really are doing," she added.

Students will synch their wristbands to MyFitnessPal, an app that can also track their daily diet. Researchers are using Fitbit tracking to examine sleep patterns as well.

When a youngster's activity level drops, researchers can send a cell phone text or Twitter message, with real-time tips on a healthy excursion or snack.

Funded by a $100,000 grant from the philanthropic arm of insurer Florida Blue, the school-based program eliminates the need to talk teenagers into trekking to the doctor's office.

"We are coming right to where they are," said program coordinator Janelle Garcia, a health educator who hopes to expand nationally if successful. "The goal is to test the feasibility."

The focus is not on weight loss, but teaching healthy habits at a critical age. Obese adolescents are much more likely to become obese adults, and run the health risks of developing diabetes, hypertension and cardiovascular disease.

Students will meet with nutrition counselors and fitness experts twice a week, as well as attend after-school sessions with a psychologist focused on behavioral change.

Such counseling is key, said Corby Martin, an associate professor at Louisiana State University’s Pennington Biomedical Research Center. Simply wearing a fitness wristband doesn't guarantee that adults will shed pounds, research has shown.

"The proliferation and availability of these devices and apps doesn't necessarily mean that it's going to miraculously help you lose body weight, increase your activity and be healthier. That takes a lot of work," said Martin, a spokesman for the Obesity Society, a scientific organization.

Teenagers and their parents may be reluctant to talk about weight problems, the Florida researchers acknowledge.

"We are fully aware that this may make some families uncomfortable," said Hernandez, who hopes an accompanying schoolwide health initiative will destigmatize the topic.

On Friday morning, 14-year-old Sierra Mieczkowski saw little downside as she arrived for a height and weight check and slipped off her black sneakers, revealing mismatched socks.

The ninth-grader, who does not know whether she will be selected for the study, said she tries to eat well and takes frequent walks with her father.

But with a wearable fitness tracker, "I could see how much I'm doing," she said, adding "and know how much I can improve."