To help fight the childhood obesity epidemic and instill healthy habits in youths, Miami-Dade County started Fit-to-Play, an after-school health and exercise curriculum held at local parks.

To examine the program’s effects, a team of University of Miami doctors did pre- and post-school year measurements tracking students’ progress.

The results? Children and teens maintained a healthy weight, lowered their blood pressure, and increased their physical fitness and nutritional knowledge, said Dr. Sarah Messiah, who is conducting the study and is a research associate professor at the University of Miami Department of Pediatrics. These results are based on measurements taken atthe beginning and end of the 2010-11 school year. The overall results for the 2011-12 and 2012-13 school year are not available yet.

“The earlier the better in terms of influencing the children to be physically active,” she said. “This program is now an evidence-based program and a resource for all children in this community that is accessible, affordable and year-round — something we haven’t really had before.”

For the study, which focused on 250 students from 6 to 14, doctors measured body-mass index, fat distribution, blood pressure, physical fitness and nutritional knowledge.

“We are trying to get the big picture by taking all of these different measurements,” Messiah said.

Body-mass index, the measurement generally used to determine if a person is obese or overweight, is based on weight and height. Children’s body-mass index is determined by using age- and sex-specific percentiles — those who are overweight are above the 85th percentile and those who are obese are above the 95th percentile.

But body-mass index measurements could be a bit misleading. More athletic children, who have built up muscle, may yield a higher weight and a high body-mass index even if they’re not obese or overweight.

“Muscle weighs more than fat,” Messiah said.

As such, doctors also administered a skinfold-measurement test that shows the percentage of body-fat composition. Fit-to-Play also has targeted blood-pressure levels.

“I was very surprised to see how many kids were pre-hypertensive and hypertensive before we started,” Messiah said.

In general, a pre-hypertensive adult has a systolic blood pressure, or the higher number of a blood-pressure measurement, greater than 120. Jennifer Irias, 7, started the program with a systolic blood pressure of 125 — a high number even for an adult. By the end of the 2011-12 school year, that rate dropped to 105.

Her diastolic blood pressure, or the lower number of a blood-pressure measurement, remained unchanged at 77, which is normal.

Like many other children in the program, Jennifer’s physical fitness and nutritional knowledge has improved significantly.

When she started the program, she could do one sit-up. Now, she can do eight. And on her nutritional-knowledge exam, she answered two more questions correctly than she did at the start of the school year.

By the end of the 2010-11 school year, 22 percent more children identified soda as an unhealthy drink versus water and 20 percent more said fruits and vegetables are healthy with every meal.

“As a nation, as a whole, we are very nutritionally illiterate,” Messiah said. “But with very little time, kids learn.”