The nationwide survey found that people from lower socioeconomic backgrounds are less likely to know about the link, and men are less likely than women to be aware of the increased risk of cancer caused by obesity.
Dr Julie Sharp, Cancer Research UK’s head of health information, said: “A quarter of all UK adults are estimated to be obese, and this has a real impact on their risk of developing cancer.
"Eating a healthy balanced diet and becoming more active can help people to keep a healthy weight. And encouraging children and teenagers to do the same can help them keep to a healthy weight later on in life.”
As well as general ignorance about obesity and cancer, the survey showed that more than three-quarters (78 per cent) of those asked didn’t know obesity was linked specifically to ovarian cancer.
More than two thirds (69 per cent) didn’t know there was a link with breast cancer and more than half (53 per cent) didn’t know pancreatic cancer was linked to obesity.
There was better awareness of the link with bowel cancer with 60 per cent of those surveyed knowing the association and 55 per cent of people linked obesity with liver cancer.
Being overweight or obese is the single biggest preventable cause of cancer after smoking and is linked to an estimated 18,100 cancer cases each year in the UK. Being overweight or obese is linked to 10 types of cancers, including breast, bowel, womb and oesophageal.
Alison Cox, director of prevention at Cancer Research UK, said: “Cancer isn’t at the forefront of people’s minds when talking about obesity and that’s really concerning. Few understand that excess weight increases the risk of several cancers, including some of the most common such as breast cancer.
“It’s the Government’s responsibility to inform the public of the link and also to take action to tackle the obesity epidemic, starting with the health of the nation’s children. It’s great the Government’s childhood obesity plan includes a sugary drinks tax, but it’s not enough to curb the rising tide of ill-health.
“The Government acknowledges that marketing junk food to kids is a problem and has removed these adverts during children’s programming. We also need to see these restrictions during family viewing time before 9pm if we want to make a difference to children’s health.”
The study was conducted by the Policy Research Centre for Cancer Prevention at Cancer Research UK.