Obese children are almost six times more likely to develop high blood pressure compared to their healthy-weight peers, a new study has shown.

High blood pressure, also known as hypertension, causes silent damage to the blood vessels and the heart. If left untreated, this damage progresses over time and may cause a range of problems, including atherosclerosis (hardening of the arteries) and kidney damage. It is also a major risk factor for heart disease.

German researchers looked at over 22,000 children and teenagers. All had their blood pressure, body mass index (BMI), waist circumference, waist-to-height ratio, body fat percentage and skinfold thickness measured.

"These measures are simple, inexpensive, risk free and can be used in offices, schools and at home. However, they must be performed correctly and age and gender specific cut-off values must be used," noted the study's investigator, Prof Peter Schwandt, of the Ludwig-Maximilian University of Munich-Nuremberg.

The study found that young people who were obese had a much greater risk of developing prehypertension and hypertension. Prehypertension refers to a slightly higher blood pressure that will more than likely develop into full hypertension if lifestyle changes are not made.

"We found that obese girls had a nearly six-fold higher risk of hypertension than normal weight girls. In obese boys the risk was more than four times greater than their normal weight counterparts," Prof Schwandt said.

This increased risk was also found when other measurements of body fat were used, such as weight-to-height ratio and elevated skinfold thickness.

Details of these findings were recently presented at the European Society of Cardiology's 2014 Congress in Barcelona.