The idea that excess weight in young children has no consequences is a myth, researchers have warned after carrying out a study into blood pressure.

According to their findings, four-year-olds who are overweight have double the risk of high blood pressure by the age of just six, increasing their future risk of suffering a heart attack or stroke.

Childhood obesity is one of the most serious public health problems globally today. World Health Organization figures show that in 2016, over 41 million children under the age of five were overweight.

Spanish researchers set out to investigate the link between excess weight and blood pressure in almost 1,800 four-year-olds. The children were followed up two years later. Their body mass index, waist circumference and blood pressure were assessed at both times.

The study found that compared to children who maintained a healthy weight between the ages of four and six, those who were already overweight or who became overweight during this time, were at least two times more likely to have high blood pressure at the age of six.

Furthermore, this risk was at least three times greater if the child had persistent abdominal obesity, which refers to excessive fat around the abdomen and stomach.

The findings applied to all of the children, irrespective of their gender or socioeconomic status.

"The myth that excess weight in children has no consequences hampers the prevention and control of this health problem. Parents need to be more physically active with young children and provide a healthy diet.

"Women should also shed extra pounds before becoming pregnant, avoid gaining excess weight during pregnancy and quit smoking, as these are all established risk factors for childhood obesity," commented the study's author, Dr Iñaki Galán, of the Carlos III Health Institute in Madrid.

In addition to the key role of parents, Dr Galán also believes that schools should include three to four hours of physical activity per week.

"There is a chain of risk, whereby overweight and obesity lead to high blood pressure, which heightens the chance of cardiovascular disease if allowed to track into adulthood. But the results show that children who return to a normal weight also regain a healthy blood pressure.

"Some paediatricians think the harms of overweight and obesity begin in adolescence, but our study shows they are mistaken. We need to detect excess weight as soon as possible, so the damaging impact on blood pressure can be reversed," he added.

Details of these findings are published in the European Journal of Preventive Cardiology.