Most people in the UK think it is healthier to relax than take exercise, a study shows.
Obesity is a major killer in the UK
They believe it is "dangerous" to be active if you are mildly overweight.
One in 10 people think they can improve their fitness by getting up to change TV channels instead of using the remote control.
The findings, by a sports dietician follow reports that Britain is facing an obesity crisis that will only be cured by huge lifestyle changes.
Dr Carrie Ruxton, who carried out the study, said the findings confirmed her theory that people in the UK are inactive.
She interviewed 3,000 people about their health and lifestyles and found 41% took part in no sport, with another 22% spending less than an hour a week taking part in some sporting activity.
Dr Ruxton said: "Obesity is a serious issue in the UK but people often forget that the cause isn't only related to what people eat.
"Lack of physical activity is a major part of the problem - and the solution.
"What I found most intriguing about the results was that people had got the messages about how much physical activity they should be taking, and what types of activity counted.
"But, this was not translated into personal action.
"More than 60% of people did less than one hour of exercise a week, while over half of the group surveyed spent most of their working day sitting down."
Only a third of people questioned knew that it takes three hours to burn off a large hamburger and fries.
Dr Ruxton said: "As people increasingly eat out these days, they don't know how many calories they are eating let alone how much physical activity is needed to burn those calories off.
"While nearly 60% said they didn't have time to be more active, they nevertheless found time to watch television and videos, and to play computer games for several hours a day."
Dr Ruxton was also concerned that 40% of people used their cars to take short journeys when perhaps they could walk.
"My conclusion from the survey is that people could do more to help themselves achieve a healthier weight," she said.
Three in four women and three in five men are risking poor health because of physical inactivity, according to the Health Development Agency (HDA).
Active people have a 50% lower risk of heart disease, and regular physical activity plays a role in reducing obesity, diabetes, osteoporosis and colon cancer.
HDA chief executive Paul Streets said: "We're facing a race against time to get more people to be more active.
"The best way to do this is by encouraging activity that is achievable, can easily fit into our everyday lives and importantly, one that we enjoy.
"Many people waste energy feeling guilty for not going to the gym, when instead they should think about what activity they can do easily and just do it."