BETHESDA--Children who were overweight at 9 and 11 years of age showed significant cardiovascular risk factors, according to a large study of 5,106 primary school students published in the April American Journal of Clinical Nutrition (AJCN).
"The overweight children had significantly higher blood pressure, total blood cholesterol, low density lipoprotein or LDL cholesterol, the so-called bad cholesterol, and lower high density lipoprotein cholesterol or HDL cholesterol, than their lighter peers," said Johanna T. Dwyer, D.Sc., Professor of Medicine at Tufts University Schools of Nutrition and Medicine, Boston. Her coauthors are 8 associates reporting for the Child and Adolescent Trial for Cardiovascular Health (CATCH) Collaborative Research Group, supported by funding from the National Institutes of Health.
Elevated LDL cholesterol, along with reduced HDL cholesterol, and high blood pressure, are known major risk factors for future heart disease.
"We are quite concerned that parents and schools recognize overweight is a health problem, even in children," said Dr. Dwyer.
At entry into the study, in the third grade, the prevalence for overweight in boys was slightly over 28% and, in girls, almost 30%. At follow-up, 2-1/2 years later in the fifth grade, overweight in the boys had jumped to slightly over 34% and, in girls to slightly over 30%. A student was considered overweight if he or she was above the 85th percentile in body mass index (BMI)--the standard which measures body weight as a function of height at a given age level.
"These children are on a risky track, not only for continued or greater overweight in the future, but also potentially for some very serious adult cardiovascular disease problems," added Dr. Dwyer.
"A child's weight status in the third grade," said Dr. Dwyer, "was the most powerful predictor of overweight at follow-up in the fifth grade. Another strong predictor of overweight in the fifth grade was male sex and African American race or ethnicity."
In this study, 38% of African Americans and over 25% of whites were overweight. At baseline in the third grade, the study population was 69% white, slightly over 13% African American, almost 14% Hispanic, and about 2% Asian.
"There was a larger proportion of boys and girls in the overweight category than we expected," said Dr. Dwyer. "Also, over the 2-1/2 years of the study, many more children became fat than returned to a desirable weight," she added.
During the duration of the study, 7% became overweight and 25% remained so.
"In contrast," noted Dr. Dwyer, "only 5% of the children who were overweight attained normal status. But those who lost weight or who had a lower relative weight in the third grade and remained that way, showed favorable heart disease risk factor changes. They lowered their risk."
The CATCH study involved 96 elementary schools in California, Louisiana, Minnesota, and Texas. The measurements taken in third grade and at follow-up 2-1/2 years later included height, weight, blood pressure, serum lipids, 24-hour dietary
recall for a sample of children, a 9-minute run, and a self-administered physical activity check list. The CATCH study was not designed to reduce weight.
According to the results published in the monthly peer-reviewed journal of the American Society for Clinical Nutrition, the childrens' blood pressure rose as BMI increased, and pressure differences between the 4 weight categories were significant. Weights were categorized as BMI below the 15th percentile, the 15th to the 49th percentile, the 50th to the 85th percentile, and over the 85th percentile.
As expected, performance on the 9-minute run was lowest for the overweight group, but no other differences between weight groups emerged. Total minutes of physical activity per day, minutes spent in vigorous physical activity, and time spent
viewing TV or playing video games did not vary significantly among weight categories.
"There is a special need for early intervention in children to prevent overweight and obesity, and for treatment when high BMIs are noticed," said Dr. Dwyer. "Our findings underscore the great importance of continued efforts at population-based interventions for children to prevent overweight and overfatness by promotion of physical activity and healthy eating patterns."
Journal
American Journal of Clinical Nutrition