A study of 1,111 healthy Indiana school children over a period of 4.5 years revealed that when the children's body mass index (BMI) reached or passed the 85th percentile -- the beginning of the overweight category -- the adiposity effect on blood pressure was more than four times that of normal weight children. Adiposity is fat under the skin and surrounding major organs.

The absolute value of BMI is not used to classify weight status in children, because change in BMI is normal and expected as children grow and develop. Instead, BMI percentiles are used which adjust for age and gender.

Researchers found when children reached categories of overweight or obese, the influence of adiposity on blood pressure increased.

"Higher blood pressure in childhood sets the stage for high blood pressure in adulthood," said Wanzhu Tu, Ph.D., study lead author and Professor of Biostatistics at Indiana University School of Medicine in Indianapolis, Indiana. "Targeted interventions are needed for these children. Even small decreases in BMI could yield major health benefits."

Among study participants, 14 percent of the blood pressure measurements from overweight/obese children were in prehypertensive or hypertensive levels, compared to 5 percent in normal weight children. Blood levels of leptin, a hormone in fat tissues, and heart rate had a similar pattern as blood pressure. So leptin may have played a mediating role in obesity-induced blood pressure elevation, researchers said.

The study reinforces the importance of separately considering overweight and obese children from those of normal weight; otherwise, the adiposity effect is overestimated in normal weight children and underestimated in overweight children.

"The adiposity effects on blood pressure in children are not as simple as we thought," Tu said.

On average, children in the study underwent 8.2 assessments each, for a total of 9,102 semi-annual blood pressure and height/weight assessments to determine BMI. The average enrollment age was 10.2 years, with children stratified into 10 years and under, 11-14 and 15 and older. Children with BMI percentile values over 85 percent were considered overweight and those with BMI values over 95 percent were considered obese.

"Important questions that remain unanswered are what makes the blood pressure go up when you have an increase in the BMI percentile and what mechanisms are involved in the process," Tu said. "This study wasn't set up to answer those questions."

Further study may determine how the increase in adiposity affects blood pressure and whether other factors such as leptin, insulin or inflammatory cytokines may play a role.

Healthcare providers and parents should pay attention to children's weight, Tu said. "If they see a dramatic weight gain in a child who already is overweight, they need to intervene with behavioral measures, such as dietary changes and increased physical activity, to improve overall health and minimize cardiovascular risk."

Co-authors are George J. Eckert, M.S.; Linda A. DiMeglio, M.D.; Zhangsheng Yu, Ph.D.; Jeesun Jung, Ph.D.; and J. Howard Pratt, M.D.

Note: If no author is given, the source is cited instead.

• Obesity
• Hypertension
• Diet and Weight Loss

• Child Psychology
• Dieting and Weight Control
• Child Development

• Body mass index
• Overweight
• Nutrition and pregnancy
• General fitness training
• Obesity
• Hypertension