An exercise in the art of exaggeration

Many people overstate how much physical activity they do, survey reveals

When it comes to exercise, most people indulge in the sport of wishful thinking, a survey has found.

More than a third of adults claim to keep active enough to stay healthy, but in reality only one in 20 does.

Exaggerating how much exercise we take is partly due to human nature and in part reflects the difficulty of calculating how much time has been spent in activity of the right intensity. But in some cases, there is an outright attempt to deceive, according to experts.

A report on physical activity in England, published today, is the first large-scale survey to examine how much exercise people take and compare it with how much they say they do.

Around 15,000 adults were asked to recall how much activity they had done in the previous month and 3,300 were then monitored for a further week, during which they wore an accelerometer to measure their movements.

The results showed 39 per cent of men and 29 per cent of women claimed to have met government guidelines for the minimum necessary level of physical activity – at least 30 minutes a day, five days a week doing activities that cause them to puff and/or break into a sweat.

But when the accelerometers were fitted, they showed only 6 per cent of men and 4 per cent of women actually did so.

Craig Williams, associate professor of sport and health sciences at the University of Exeter, said: "People are not very good at working out how long they have spent in exercise of sufficient intensity. They can remember going for a brisk walk or jogging or swimming but they are not so good at recalling the length of time in which they were physically active enough from a cardiothoracic or lung point of view."

Epidemiologists are now using devices such as accelerometers to weed out the cheats. But even these can be deceived. Professor Williams said: "You can fool them if you know how to do it. I have heard stories of people putting pedometers on their dog and sending it off for a run or on top of the washing machine set to the spin cycle. A computer can't tell what causes the movements – it just counts them."

Children are less prone to exaggeration, according to the survey, published by the NHS Information Centre. One in three boys and one in four girls said they were doing an hour of moderate-intensity exercise a day (twice the recommended level for adults), and the results from the accelerometer readings were similar.