The team found in a survey that people decide if they are overweight by comparing themselves to those of the same age and sex rather than by body mass index.

Half of European women feel they are overweight – but if those around them are obese they are likely to see it as normal, meaning people are more likely to be comfortable growing fat in an obese society.

The team analysed data from 27,000 European adults across 29 countries. Professor Andrew Oswald, of Warwick University, said: “The problem comes with high levels of fatness.

The danger is that obesity could spiral.

“If we all start copying each other we will end up with quite serious health problems.”