Oct. 15, 2010 -- Losing a little bit of weight can have a big impact on improving blood pressure for overweight children, according to a study.

Researchers at Regenstrief Institute in Indianapolis, led by Wanzhu Tu, PhD, looked at the relationship between weight and blood pressure in children. They tracked data on blood pressure, height, and weight of 1,113 children, with the longest follow-up exceeding a decade.

Half of the study group was male, 42% were African-American, and the average age was 10 years old. They compared the children’s body mass index (BMI) -- a measurement of height and weight -- with national data and adjusted for age, sex, and height. Children with a BMI in the 85th percentile or above were considered overweight.

The researchers found that BMI had relatively little effect on blood pressure levels until the overweight range was reached. At that point, a strong association was noted between BMI and blood pressure readings, such that even small increases in BMI resulted in large increases in blood pressure.

Systolic blood pressure is the top number of a blood pressure reading and is a measurement of the force of blood pumped out when the heart muscle contracts. A systolic blood pressure reading below 120 is considered normal. A systolic blood pressure reading of 140 is considered high.
Weight Loss Benefits

The findings suggests that in overweight children small changes in BMI can have a profound impact on blood pressure readings; losing a little weight can prove very beneficial to heart health while even gaining a little weight might prove detrimental.

“Below the 85th percentile, BMI effects on blood pressure appear to be fairly linear,” said Tu. “After the 85th, particularly after the 90th percentile, the BMI effect became noticeably stronger. Because our estimate of the BMI effect was much greater in overweight kids, the results suggest that even a modest reduction in BMI may produce a much greater benefit in blood pressure in overweight kids. Conversely, a small increase in BMI could put them at much greater risk of blood pressure elevation.”

The findings were presented at the American Heart Association’s High Blood Pressure Research 2010 Scientific Sessions in Washington, D.C.

Obesity is a major public health threat, particularly among children. According to the CDC, an estimated 17% of children and adolescents between ages 2 and 19 are considered clinically obese, meaning they have a BMI of 30. Obesity increased among preschoolers from 5% to 10.4% from 1980 to 2008; it jumped from 6.5% to 19.6% among the 6- to 11-year-old group and increased from 5% to 18.1% among those ages 12 to 19 during that time period.

Obese children are likely to become obese adults, increasing their risk for high blood pressure and heart disease. Other research has shown an association between BMI and blood pressure and reports reflect high blood pressure among children rising in parallel with childhood obesity rates. A 2007 study published in Circulation, reported that between 1988 and 2002, prehypertension increased among children and adolescents by 2.3% and hypertension increased by 1%.

This study was presented at a medical conference. The findings should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.