Obese people may have found a good excuse for not going the extra mile.
It seems that the heavier you are, the greater your brain perceives distances to be.
Tests showed that a person weighing 23 stone sees objects as being twice as far away as someone of nine stone.
The effect also applies to hill gradients. For a heavier individual, a hill will appear steeper than it does to a slim neighbour – another reason for taking the lift instead of the stairs. Scientists believe the strange phenomenon is a survival mechanism inherited from our distant past. It helps us evaluate testing situations in a flash, without having to think about them.
But it may also work against efforts to persuade overweight people to be more active.
Psychologist Dr Jessica Witt, from Colorado State University in the US, said: “Effort and performance influences perception.
“People who weigh more than others see distances as farther and hills as steeper, the idea being that if you have to carry this extra load that also impacts your perception. And yes, it cannot be controlled, it is out of your hands.”
Dr Witt was talking at the annual meeting of the American Association for the Advancement of Science, in Washington DC.