A large section of Britons do not take their obesity seriously and have no idea of what constitutes a healthy weight, says the Association for the Study of Obesity.
A survey by the charity found more than a third of British adults who are obese think they are merely overweight, while a fifth of those who are overweight believe they are healthy.
The group said that seven out of 10 adults are obese in some parts of the UK and the figure could rise by 2030.
Rather than considering obesity as a medical condition, Britons mostly link it to lifestyle choices. The research highlights the need for better education about obesity, its treatment and effects in the UK.
With less than a fifth of UK residents identifying obesity as a disease, the study notes that Britons are in denial compared to counterparts in Europe.
Professor Pinki Sahota, deputy chair of The Association for the Study of Obesity, told SkyNews: "Obesity is one of the fastest growing threats to the health and well-being of our society.
"And yet, this survey shows that many people still appear to have little understanding of what equals a healthy weight."
The World Health Organization has projected that 74% of men and 64% of women in the UK will be overweight by 2030.
According to UK government estimates, the cost of obesity will rise to £50bn ($78bn) by 2053, placing a heavy strain on the national health service.
A Body Mass Index (obtained by dividing your weight in kilos by your height in metres squared) above 30 is considered as obese but is not recognised as such by many.
In a public survey conducted by SkyNews, most people dismissed BMI, which is at present the only available measure of obesity.
The UK also has the second-highest proportion of overweight children as compared to 28 other countries, claimed a study undertaken by Leeds Beckett University recently.