Leading UK doctors are calling on the Government to reclassify obesity as a disease in a bid to tackle Britons’ rapidly expanding waistlines.

The Royal College of Physicians (RCP) says it has come to the conclusion that obesity “isn’t a lifestyle choice” but instead depends on genetic predisposition and environmental factors.

“Recognising it as a disease allows people to see they have a disease and reduces the stigma of having obesity,” Andrew Goddard, President of the RCP, told Sky News.

How bad is the problem?

Nearly a third of adults in the UK are obese, triple the number since 1980. The NHS spends around £6bn a year treating the condition, which is responsible for more than 30,000 deaths a year.

According to the National Obesity Forum, the four most common health problems related to being overweight are high blood pressure, coronary heart disease, type 2 diabetes and some forms of cancer.

How does the UK compare with the rest of the world?

The average body mass index (BMI) of people in the UK is 27.3, which is overweight, according to data from the World Health Organization. This makes the UK the 24th most obese country in the world, in joint place with Greece, South Africa and Saint Vincent and the Grenadines.

At the top of the list is Nauru, Mexico, New Zealand and Kuwait, the only countries with average BMIs of more than 30, classified as obese. Eritrea, meanwhile, had the lowest average BMI at 20.5, a healthy weight.

Why are Britons so fat?

Soaring obesity rates have been blamed on modern lifestyles, with most people having easy access to high-calorie foods and sedentary jobs. Individuals have long been blamed for bad dietary habits - but now leading medical experts are insisting the matter is not that simple.

RCP president Goddard tells The Daily Telegraph: “It is not a lifestyle choice caused by individual greed, but a disease caused by health inequalities, genetic influences and social factors.”

That view is shared by Professor Rachel Batterham, who specialises in obesity research for University College London. “We know the biology now and there are over 100 DNA that have been identified showing how some people will develop obesity and others will be protected,” she says.

However, David Buck from health think-tank The Kings Fund says: “Obesity isn’t a disease, it’s a condition, an outcome. I am slightly overweight, according to government statistics, but I don’t see myself as suffering with a disease. It’s because of the environment I live in, the choices I make.”