Shock new figures show the average resident in Greater London spends more than 17 hours on their backsides every day.
A study found the daily commute, a day at the office, and an evening in front of the TV means they spend hardly any time on their feet.
It emerged the typical working adult in the capital spends four hours and 55 minutes at their desk, and a further three hours and two minutes parked in front of the TV.
Once home they will sit down again to use a laptop or home computer for another two hours and 36 minutes.
The statistics also showed that 56 per cent of residents exercised for just a few minutes every day - walking to and from their parked car.
Meal times mean people sit down for a further 23 minutes, while one hour and 22 minutes are dedicated to playing computer games.
Weight Watchers UK, which conducted the poll of 3,000 adults across the UK in conjunction with its get active! campaign, put the results down to the recession and longer working hours.
Company dietician Zoe Hellman said: ''In a recession we have to work harder and for longer hours to make ends meet, so we therefore have less time and money to spend on exercise - but to spend over half our day sitting down is a health bomb waiting to happen.
"Incredibly the average person only does 50 minutes of exercise each week - that's just a quarter of what is recommended for a healthy lifestyle.
"We know that it can seem difficult to find the time to exercise, but there are ways to introduce it into even the busiest lifestyles.
"Walking up the stairs instead of taking the lift, running from the tube instead of walking, parking further from the shops and walking for 30 minutes at lunchtime instead of sitting at the desk are all free and easy ways of keeping fit.''
The research, carried out this week, shows that Londoners spend an hour and 41 minutes on public transport, and a staggering one hour and 57 minutes in the car.
Finally, before settling down to sleep at night, Londoners spend an hour and 25 minutes reading books, magazines or newspapers.
The picture is no brighter elsewhere in the UK.
More than half of people admitted that while they should exercise more, it is difficult to find the time
And 52 per cent of folk freely admit that on most days the only exercise they get is the short stroll between their house and car, nursery and car, or work and car.
Four in 10 people claim their long working hours are to blame for their lack of exercise, while the same number also attribute a lack of energy for the slump.
A third of lazy people simply can't be bothered to exercise more, while a quarter blame the quantity of housework they have to get through.
A fifth of parents say the children take up too much of their time, and over half of us are simply too exhausted by the end of the day to do any exercise.
Finally, whilst 12 per cent reckon they are happy the way they are, more than one in ten of us say the last thing we want to do is to exercise after a long commute.
It follows continued warnings from the Government about obesity levels and the importance of at least 30 minutes' exercise per day.
Zoe Hellman added: "Half an hour's exercise each evening would actually help workers to wind down and de-stress, and could even induce a good night's sleep afterwards.
"Mostly, this lack of exercise and movement is down to habit. People become so used to relaxing in front of the TV at the end of a busy day they choose that over a quick short jog or gym session.
"But exercise also has an important role in helping people to lose weight and for keeping your weight in check, in addition to the long term health benefits of being active."
The poll also shows that 37 per cent of people reckon they would exercise more if they worked shorter hours, and one in 10 would make more of an effort if they lived closer to the gym.
Astonishingly, 20 per cent of those polled say they aren't fit enough to exercise - and 17 per cent feel too fat.
When people do summon up enough energy to do a bit of moderate exercise, the top three choices are walking (43%), jogging (20%) and going to the gym (16%).
Swimming and cycling are also favoured activities for one in five Brits.
And when it comes to keeping fit - men are more likely to exercise to get fit and maintain good health, whereas women are most concerned about losing weight.