GPs should measure children's body mass index (BMI) to help curb the growing obesity epidemic, leading academics have said.
Obese children pose the threat of a "disease burden" to the population and their parents often do not recognise obesity in their children, they said.
Since children use primary care services about once a year, GPs should use the opportunity to measure their BMI, according to the researchers at University College London's Institute of Child Health.
They made their comments after a study, published on bmj.com, found that obese children have a significantly higher chance of getting heart disease than children of a normal weight.
In an accompanying editorial, Professor Russell Viner and research fellow Lee Hudson write: "Children in most countries visit primary care about once a year, and parents often do not recognise obesity or the associated risks. Opportunistic measurement of BMI and comorbidities related to obesity in primary care may be a useful first step in helping families move towards tackling childhood obesity."
The study, conducted by academics at the University of Oxford, examined data from 63 research papers published between 2000 and 2011 which studied almost 50,000 children in "highly developed" countries.
Obese children have several risk factors for heart disease including raised blood pressure, cholesterol and blood sugar levels, and a thickening of the heart muscle, compared with normal weight children, they found.
The authors conclude: "Weight, and especially obesity, has a significant effect on the risk parameters for cardiovascular disease that are present in children from age five years. This effect could give them a head start on their normal and even overweight classmates for future cardiovascular disease, diabetes and stroke."
A Department of Health spokesman said: "England has some of the highest levels of obesity in Europe. To turn this round we need action at every level.
"Through Change4Life we are reaching more and more children and families with information, ideas and things they can do to eat well, keep moving and live longer. We are also are working with major retailers and food manufacturers through the Responsibility Deal to help people to cut their calories."