Many obese people are in denial about their size and do not want to lose weight even if it would improve their health, according to a recent British poll.

More than half of 4,000 people questioned by the charity Cancer Research UK were overweight or obese but a quarter of them were not concerned about losing weight.

"It's worrying to think that people are in denial about their weight -- people who are carrying extra weight face significant health risks including cancer," said Dr Lesley Walker, the charity's director of information.

Nearly 80 percent of the overweight and obese people questioned in the poll did not understand the importance of having a healthy body weight. Many also did not know their correct weight or that excess kilos increase the risk of cancer.

Obesity, which affects about 300 million people worldwide, also raises the risk of diabetes, heart disease and strokes.

It is calculated using body mass index (BMI) -- dividing weight in kilograms by height in metres squared. A BMI of more than 30 is considered obese, more than 40 is very severe.

In some Western countries, up to 8 percent of total healthcare costs are attributable to obesity and related problems. It is a leading cause of preventable death.

"These results show far too many of those at greatest risk are choosing to ignore their weight," Walker added. "They are unaware of their increased risk of cancer and unaware of many of the benefits of a healthy lifestyle."

Cancer Research UK and the charity Weight Concern said people who are overweight or obese should try to eat at the same time every day, choose reduced-fat foods, exercise, select healthy snacks, limit alcohol, and watch their portion sizes.

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