People who are obese are at increased risk of heart disease

Leading scientists meeting in Prague said obesity was fast becoming the world's biggest health problem.

They called for controls on marketing and television advertising for children, and clear labelling to show which foods were healthy.

They also want a new EU agency charged with preventing obesity, and a common public health policy across the union.

At a press conference, they stressed that even a small reduction in weight can have significant health benefits.

Obesity is linked to illnesses such as heart disease, stroke and diabetes. It is estimated to cause 70,000 new cancer cases in Europe every year.

Professor Claude Bouchard, president of the International Association for the Study of Obesity, said: "Obesity has now become a strong candidate for being the number one health problem mankind is facing."

Cinderella area

But he said funding for research was focused on other areas, with obesity attracting a relatively small amount of investment.

According to the International Obesity Task Force, the prevalence of obesity has increased by up by 10-40% in the majority of European countries in the past 10 years.

Professor Vojtech Hainer, of the European Association for the Study of Obesity, said Central Europe had the highest rates of obesity within the newly expanded EU and more collaboration with Western European countries will be needed to tackle it.

The first European guidelines for managing obesity, launched at the conference, stress the importance of a balanced diet and exercise and setting realistic weight loss goals.

According to these guidelines, a weight loss of 5-15% is realistic, and has proven health benefits.

Reducing calories by about 600 a day would lead to a weekly weight loss of about half a kilo (1.1 lbs) a week, according to the guidelines.

The conference comes days after the World Health Organisation adopted an unprecedented policy on diet and health to tackle a global increase in obesity.

The voluntary plan was hammered out at talks in Geneva in the face of stiff opposition from lobbies such as the sugar-producing nations.

It includes guidelines for urban planners on encouraging exercise as well as advice on healthy eating.