Joint campaign highlights dangers of 'spare tyres'
A survey to launch the 'Active Fat' campaign found that 71 per cent of respondents admitted to carrying excess weight around their middle.
Yet 97 per cent did not realise that this extra fat generates higher levels of oestrogen, placing people at risk of cancer, type-2 diabetes and heart disease.
More than half of the 2,085 respondents - 57 per cent of women and 55 per cent of men - also overestimated the waist measurement at which excess weight begins to become a risk.
Women are at risk of type-2 diabetes and heart disease if their waist measures more than 80cm (31.5 inches), while men are at risk at more than 94cm (37 inches).
Only 44 per cent of people had increased their exercise levels in an attempt to reduce their waistlines.
In light of these findings, the three national charities are urging people to measure their waistlines and make the necessary lifestyle changes if they are carrying too much weight around their middle.
Professor Jane Wardle, director of Cancer Research UK's Health Behaviour Research Centre at University College London, said: "Little changes that can become daily habits are the best, as they usually require less effort and can act as the building blocks of a much bigger lifestyle picture.
"Waist size is likely to increase throughout life, so whatever your age, today is a good day to start improving your health."
Dr Mike Knapton, associate medical director for the British Heart Foundation, said that excess weight around the waist is a "major" health hazard.
"Wrapping a tape measure around your middle takes just a few seconds, but it could be your vital first step towards a healthier future," he advised.
The charities also want the European Parliament to bring in a single front-of-pack food labelling system across the EU, so that all consumers can easily choose healthier options when shopping.
Libby Dowling, care advisor at Diabetes UK, said: "We need one system that includes traffic light colours to help busy supermarket shoppers make informed food choices."