"We were surprised that the children had developed vascular abnormalities at such a young age – and by how readily these could be reversed with simple lifestyle measures," says Kam S. Woo, M.D., chair and professor of medicine and therapeutics and a consultant cardiologist at The Chinese University of Hong Kong.
The researchers studied 54 boys and 28 girls, average age 9.9 years. Based on body mass index (BMI), 28 were deemed overweight and 54 were obese.
The study did not include children with a family history of early heart disease, but the youngsters already showed signs of early atherosclerosis. Using ultrasound, the researchers measured the ability of the brachial artery in the arm to expand in response to increased blood flow. This response is called endothelium-dependent dilation, and is a measure of an artery's reactivity.
A less-reactive artery is a sign of vascular damage and an early feature of atherosclerosis, the disease process that underlies heart disease and stroke. The researchers also used ultrasound to measure the thickness of inner layers in the wall of the carotid arteries, which are in the neck and supply blood to the brain. This measure is a well-established, noninvasive way to assess plaque build-up in the arteries and monitor its progression.
The children hadn't entered puberty, but their vascular test results "matched those of a 45-year-old adult who had been smoking for more than 10 years," Woo said. "Compared to normal-weight children, by adulthood they are three to five times more likely to suffer a heart attack or stroke before age 65."
To assess whether these risk factors could be improved, the researchers divided the children into two groups – diet-only or diet-plus-exercise.
For the first six weeks, all the children met with a dietitian twice a week and followed a 900–1,200 calorie diet that was low in fat and high in complex carbohydrates. Children in the diet-plus-exercise group met with an exercise trainer weekly and were led through a 75-minute program twice a week that included aerobics, resistance training and agility exercises.
After six weeks, overweight and obese children in both groups had significantly reduced their waist-hip ratio, lowered their total cholesterol and increased their endothelium-dependent dilation. Diet and exercise were associated with a significantly greater improvement in endothelial function than diet alone. Endothelial function in children in the diet-plus-exercise group improved from 6.8 to 8 percent; it improved from 6.9 to 7.5 percent for the diet-only group.
During the next year, the children met the dietitian twice a month and were 80 percent successful in following the prescribed balanced diet. Twenty-two children in the diet-and-exercise group continued training once a week; 19 stopped. At the end of the year, the children who continued exercising had significantly less thickening of the carotid wall and more improvements in body fat content and lipid measures. By the end of the year, the endothelium-dependent dilation increased significantly in the initial exercise group (to 7.4 percent) and to 8.6 percent in those who kept exercising.
"This highlights the importance of regular exercise in preventing obesity-related vascular dysfunction in children," Woo said. According to government surveys, 15.3 percent of children aged 6–11 in the United States are overweight or obese. Almost half of young people get no regular exercise, Woo said.
"Adopting a healthy lifestyle in childhood is the most cost-effective and practical way to prevent heart disease in adults," Woo said.
Co-authors are Ping Chook, M.D.; Chung W. Yu, Ph.D.; Rita Y.T. Sung, M.D.; Mu Qiao, M.S.; Sophie S.F. Leung, M.D.; Christopher W.K. Lam, Ph.D.; Con Metreweli, M.D.; and David S. Celermajer, Ph.D.
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