According to a poll in the UK more than a quarter of obese and overweight people do not want to lose weight, and many were unable to identify their weight category.
The survey by Cancer Research UK also found many more were unaware of the benefits of a healthy lifestyle and that being overweight increased their risk of cancer.
The findings coincide with the charity and Weight Concern publication of 10 tips to help people manage their weight.
They include keeping regular meal times, walking 10,000 steps a day and snacking healthily.
Although more than half of the 4,000 people polled were overweight or obese, 26% of them said they did not want to lose weight.
Of even more concern was that as many as 87% of obese and 32% of overweight people were unable to identify their weight category.
Three-quarters said they did not know there was a link between cancer and weight and nearly half did not believe eating healthily could reduce cancer risk.
Obesity is linked with an increased risk of bowel, kidney, oesophageal and stomach cancers, as well as cancer of the womb and breast cancer in post-menopausal women.
Dr Lesley Walker, director of cancer information at Cancer Research UK, says it is a cause for concern that so many people are in denial about their weight, as those who carry extra weight face significant health risks including cancer.
Dr Walker says that obesity is one of the biggest known preventable causes of cancer for those who do not smoke.
Weight Concern executive director Caroline Swain is reported to have said that the lack of concern about obesity was a worry and education and support were vital in tackling the alarming rise in obesity.
The organisation advises people to keep to a meal routine, choose reduced fat versions of food, pack a healthy snack and always watch portion size as well as fat and sugar content of foods and drinks.
They advise drinking water and remembering that alcohol is high in calories.
Eat food slowly they say and include at least five portions of fruit and vegetables each day.
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