CHICAGO -- A study of 17 middle school students suggests that physical fitness gains made by obese children who participated in a lifestyle-focused physical education class during the school year were lost after the three-month summer break, according to a report in the June issue of Archives of Pediatrics & Adolescent Medicine, one of the Journal of the American Medical Association (JAMA)/Archives journals.

Children increasingly live in an environment with reduced amounts of physical activity coupled with easy access to calories, according to background information in the article that was posted on the Web site www.medicalnewstoday.com. This can result in obesity, poor cardiovascular fitness, insulin resistance, type 2 diabetes, high cholesterol and hypertension.

Dr. Aaron L. Carrel and colleagues at the University of Wisconsin Children’s Hospital in Madison, WI, previously conducted a randomized controlled trial in which 17 overweight children over the age of 12 were assigned to participate in a lifestyle-focused, fitness-oriented physical education class for nine months. At the end of the trial, students in the class achieved significant improvements in cardiovascular fitness and also had reduced fasting insulin levels, which indicate a lower risk for diabetes. For the new study, the same children—all of whom remained at the same school and repeated the fitness class—were assessed again at the beginning and at the end of the next school year.

“Improvements seen during the nine-month school-year intervention in cardiovascular fitness, fasting insulin levels and body composition were lost during the three-month summer break,” the authors write. During the break, average fitness level as measured by maximum oxygen consumption—the amount of oxygen the body can use, with higher levels indicating better fitness—decreased by 3.2 milliliters per kilogram per minute. Percentage of body fat increased by an average of 1.3 percent, and fasting insulin levels also increased.

“Developing and evaluating interventions to influence students’ opportunities for healthful choices has been a focus of school-based health promotion research, including nutrition programs and physical education,” the authors write. “However, when interventions occur in a school-based setting, and are confined to the school year, an inherent question is one of sustainability.”

The children were not given any instructions regarding exercise over the summer, creating three months of unsupervised activity, the authors note. “These data show that in children, efforts to improve insulin sensitivity and reduce risk of type 2 diabetes mellitus and other morbidities of insulin resistance should include exercise intervention in a sustained manner to improve cardiovascular fitness throughout the year, not just during the school year,” they conclude.