'Little understanding' of obesity
More than a third (36%) of adults in the UK who think they are merely overweight are actually clinically obese and at risk of major health problems, research has found.
Meanwhile a fifth of Britons (21%) who consider themselves normal or healthy weight are actually officially classified as being overweight, according to the international study of more than 14,000 people.
The survey, which saw people in seven EU countries quizzed, found that many Britons are in denial about their true weight - but they were also more likely than many of their European counterparts to link rising levels of obesity to poor lifestyle choices, rather than blaming genetics or health problems.
While two-thirds (65%) of French people questioned said they would describe obesity as a disease, and nearly half (46%) of Belgians did, less than a fifth (18%) of UK residents did so - the lowest proportion in Europe.
Britons also had a higher level of awareness than others about the health risks of being too heavy.
Of the lifestyle and environmental factors, 94% said poor diet was to blame, while 91% identified lack of physical activity, and most r espondents in the UK were able to correctly identify health problems such as diabetes, heart disease, high blood pressure, and joint and back pain as being related to obesity.
A third (37%) said they believe obesity is psychological, with a quarter (25%) describing it as a genetic disorder.
Older respondents (those aged 55 plus) were less likely than younger ones to agree that obesity is a psychological problem, at 32%.
Obesity is commonly defined as a body mass index (BMI) of 30 or more, while people with a BMI of 25 or more are considered overweight.
More than three in five (62%) were classed as obese in England in 2013 and it has been estimated that the problem will cost the NHS £9.7 billion by 2050, with wider costs to society reaching £49.9 billion a year, according to Public Health England.
The survey was conducted by Opinium in collaboration with the European Association for the Study of Obesity (EASO), and saw people questioned in Belgium, Denmark, Finland, France, Germany, Italy and the UK.
Professor Pinki Sahota, deputy chairwoman of the Association for the Study of Obesity, said the new Government, policymakers and health authorities should be "greatly concerned" by the survey's findings.
She said: "Obesity is one of the fastest growing threats to the health and well-being of our society.
"In some parts of the UK as many as seven out of 10 adults are now classified as overweight or obese and by 2030 it is predicted that this could rise even higher.
"And yet, this survey shows that many people still appear to have little understanding of what equals a healthy weight.
"It confirms much greater effort is needed to educate people about the fact obesity is a disease. It is clear the vast majority of people regard obesity as a problem purely of personal lifestyle, rather than recognising there are other underlying issues which society needs to address.
"There is an urgent need for better education to improve understanding and to inform overweight or obese people about the support and, if appropriate, treatments that can help them avoid the many secondary conditions like heart disease.
"Major policy change is needed and a first step must be improving awareness of the challenge faced."