Regular exercise can help obese children shrink more than just their waistlines, new research shows. The activity also can help them to reduce -- and even reverse -- their risk of developing cardiovascular disease, including hardening of the arteries.

The research, conducted at the University of Rostock in Germany, appears in the Nov. 7, 2006 edition of the Journal of the American College of Cardiology.

"We think the most important message is that atherosclerosis -- hardening of the arteries -- starts during childhood in the presence of such risk factors as obesity and sedentary lifestyle," said lead researcher Andreas Alexander Meyer, MD, a pediatrician and pediatric cardiologist at the University of Rostock Children's Hospital. "Regular exercise is one of the most important activities we can do on our own to reduce the risk and reverse the early development of atherosclerosis."

This information is vital, Dr. Meyer said, as the need continues to grow to help children protect their health without becoming dependent upon prescription medications. According to the World Health Organization, childhood obesity already is "epidemic in some areas and on the rise in others." Worldwide, an estimated 22 million children under age 5 are overweight. In some countries, including the United States, more than 30 percent of all children are considered obese.

For their study, Dr. Meyer and his colleagues defined obesity as having a body mass index (BMI) in excess of the 97th percentile for German children. BMI is determined by a mathematical formula that uses height and weight to calculate body fat.

In adults, a BMI between 18 and 24.9 is considered normal, a BMI between 25 and 29.9 is considered overweight, and a BMI of 30 or more is considered obese. Specific ranges don't exist for children, but most of the teen-agers in the University of Rostock study had BMIs ranging from 24 to 35.

Compared with normal children, the obese youths also already were showing signs of early hardening of the arteries as well as thickening of the arterial lining where atherosclerosis originates.

For the study, the researchers randomly assigned 67 obese teens to one of two groups. The first group exercised three times per week for six months. The youths participated in an hour of swimming and aqua aerobics on Mondays, 90 minutes of team sports on Wednesdays, and 60 minutes of walking on Fridays. The other teens added no exercise to their normal routines.

After six months, the researchers found that the youths who were exercising regularly had significantly improved the flexibility of their arteries, allowing the arteries to carry more oxygen-rich blood to the body when needed. The teens also had shrunk the expanded inner layer of their arteries and reduced several other risk factors for cardiovascular disease, including lowering their BMIs, cutting triglyceride and cholesterol levels, and lowering blood pressure.

Previous research has indicated that the heart-healthy benefits of exercise wear off if regular activity is discontinued, Dr. Meyer said, so encouraging all children to maintain an exercise routine is important.

"We think that 90 minutes of exercise, three times per week is the minimum children need to reduce their cardiovascular risk," Dr. Meyer said. "And it's important that children enjoy exercise, so we recommend games like soccer, football, basketball and swimming -- especially for obese children.

"Low perseverance and motivation seem to be distinctive for overweight children," he said, noting his concern over the number of teens who dropped out of the six-month study. "We have intensive talks with children and their parents about their medical status and vascular changes. We let them know that it is their own decision to change their prognosis."

To help children to monitor their success, Dr. Meyer recommends regular visits to the pediatrician combined with continuous support and encouragement from parents.

Albert P. Rocchini, MD, did not participate in the research, but is a pediatric cardiologist at C.S. Mott Children's Hospital at the University of Michigan. Dr. Rocchini said he, too, is concerned about motivating overweight children, especially teen-agers, to lead healthier lives.

"That's a very difficult problem," Dr. Rocchini said. "Sometimes education helps to let them know that they aren't invincible and they do have factors that will affect them very adversely as they grow older. We want young people to understand that now is the time to start dealing with health issues before they become permanent. But it takes time to get through to them."

Studies like this help with the education process, Dr. Rocchini said, because they show how and why carrying extra weight can lead to cardiovascular disease. Not all previous studies have documented vascular changes in obese children.

"I would take this as good and bad news," Dr Rocchini said of the study. "The bad news is, (early evidence of disease) is there, but the good news is it's not fixed and permanent. There's something you can do to make it better. That's the important message to share with people."

Dr. Meyer reports no disclosures with this research. Funding comes from a University of Rostock Medical Faculty research program grant.