The number of overweight and obese people worldwide is set to increase by half over the next ten years, heightening their health risks, the World Health Organisation warned.

Around one billion people are currently affected worldwide, and the figure is set to rise to 1.5 billion by 2015 if current trends continue, the WHO said ahead of annual World Heart Day, which is marked Sunday.

Excessive weight and Obesity - the next step up - are major risk factors for cardiovascular disease, which is the number one cause of death worldwide, claiming more than 17 million lives a year.

Long seen as a problem of the rich world, it is on the increase in poorer nations.

The change is tied to a global shift in diet towards foods containing more fat, salt and sugar, said the WHO.

It also highlighted reduced physical activity because of the sedentary nature of many modern jobs, plus growing reliance on motorised transport particularly in sprawling cities.

According to the UN health agency, more than 75 percent of women over the age of 30 are now overweight in countries as diverse as Barbados, Egypt, Malta, Mexico, South Africa, Turkey, and the United States.

Estimates are similar for men, with more than three-quarters now overweight in, for example, Argentina, Germany, Greece, Kuwait, New Zealand, Samoa, and Britain.

“The sheer magnitude of the overweight and Obesity problem is staggering,” said Catherine Le Gales-Camus, the head of the WHO’s noncommunicable diseases and mental health division, in a statement.

“The rapid increase of overweight and Obesity in many low and middle income countries foretells an overwhelming chronic disease burden in these countries in the next 10 to 20 years, if action is not taken now.”

Excessive weight increases the risk of heart disease, stroke, diabetes and other chronic diseases.

“The real tragedy is that overweight and Obesity, and their related chronic diseases, are largely preventable,” said Robert Beaglehole, a senior WHO expert.

“Approximately 80 percent of heart disease, stroke, and type 2 diabetes, and 40 percent of cancer could be avoided through healthy diet, regular physical activity and avoidance of tobacco use.”