About a quarter of British men are in denial about their weight problem, according to a recent survey released.

Although national statistics say as many as 65 percent of men are overweight or obese, in a poll of 2,000 of them, 25 percent would not admit they needed to lose weight.

About 65 percent of those questioned did not know being overweight increased their risk of developing cancer and 75 percent were not aware of the benefit of exercise.

"In the space of 10 years, the rate of obesity for British men has increased two thirds," said Professor Jane Wardle, of the charity Cancer Research UK which conducted the poll.

"Women are overweight too but our research shows that more of them know they have a problem and that's the first step in putting it right."

The number of overweight and obese people worldwide has risen to epidemic proportions. It is calculated using the so-called Body Mass Index (BMI) obtained by dividing weight in kilograms by height in meters squared.

A BMI of more than 30 is considered obese. More than 35 is severely obese and more than 40 is very severe.

Obesity is linked to a number of health complications including Type 2 diabetes, osteoarthritis, heart disease, strokes and certain cancers. Psychological problems include low self-esteem and depression.

The causes of obesity are varied but in most cases it is due to unhealthy eating and lack of exercise. Psychological factors such as negative emotions and boredom or depression play a role along with physical problems and genetics.

"In men who don't smoke, obesity is one of the biggest known causes of preventable cancer," said Dr Lesley Walker of Cancer Research UK.

"With rates of obesity for UK men growing faster than anywhere else in Europe, we are sounding a wake-up call to all men and their partners to become more active, eat healthier diets and make sensible lifestyle choices."