Overweight people who are deemed "healthy" are still at a higher risk of coronary heart disease, researchers have found.

The study found that overweight or obese people are no less at risk from the disease even if they have a healthy blood pressure, blood sugar and cholesterol levels.

"Our findings suggest that if a patient is overweight or obese, all efforts should be made to help them get back to a healthy weight, regardless of other factors," said Dr Camille Lassale, lead author of the report.

Researchers, led by experts at Imperial College London and the University of Cambridge, examined data from the European Prospective Investigation into Cancer and Nutrition study of half a million people.

They examined participants' body mass index (BMI) and whether they were metabolically "healthy" or "unhealthy" - people were classed as unhealthy if they had three or more of a number of metabolic markers, including; high blood pressure, high blood sugar, low levels of HDL cholesterol or an "elevated" waist circumference.

After adjusting for a number of factors, the researchers found that compared to the healthy normal weight group, those classed as unhealthy had more than double the risk of coronary heart disease whether they were normal weight, overweight or obese.

And even overweight and obese people who were deemed "healthy" by their metabolic markers carried a higher risk.

When compared to those who are of a healthy weight, being classed as healthy but overweight carries a 26% increased risk of coronary heart disease and being obese carries a 28% increased risk, according to the new study published in European Heart Journal.

Dr Lassale said: "Our findings challenge the concept of the 'healthy obese'. The research shows that those overweight individuals who appear to be otherwise healthy are still at increased risk of heart disease."

Coronary heart disease occurs when the coronary arteries become narrowed by a gradual build-up of fatty material. The main symptoms include angina, heart attacks and heart failure.

Commenting on the study Professor Metin Avkiran, associate medical director at the British Heart Foundation which part-funded the research, said: "Coronary heart disease - the cause of heart attacks and angina - is the UK's single biggest killer. But there are steps you can take to lower your risk.

"The take-home message here is that maintaining a healthy body weight is a key step towards maintaining a healthy heart."