Less than half of women thought they could run to catch a bus without getting out of breath, according to a health charity.
One in five adults said they could only manage to run 100 metres.
The “worrying” figures were released by the British Heart Foundation (BHF) which polled 2,000 adults about their level of fitness and how much exercise they do.
Two fifths of men also said they would be out of puff if they chased a bus.
Just under half of adults thought they could manage to run half a mile, according to the survey, and three out of ten said the last time they had managed that distance was a decade ago.
The same number confessed that tackling a few flights of stairs would get them out of breath.
More than a quarter of people said they thought you had to be really fit and healthy to go running.
The charity’s senior cardiac nurse Christopher Allen commented: ‘These statistics are concerning and paint a worrying picture about the nation’s fitness levels.”
He added: “Heart disease can affect anyone at any age, but keeping physically active is one of the best ways to help build a strong and healthy heart so we shouldn’t ignore the benefits.”
The survey, which the BFH released as it launched a challenge to people to run their own personal marathon by running a total of 26.2 miles throughout May.
The figures come as a major report published in the Lancet predicting the magnitude of the obesity timebomb in the UK.
The report, which looked at global obesity, predicted that the UK would have the highest level of obese women in Europe by 2015.
Women in the UK already have the third highest body mass index (BMI) rate in Europe and men with the tenth highest European BMI, the report found.
Already a fifth of the world’s heaviest people live in just six countries including the UK. The others are Australia, Canada, Ireland, New Zealand and the US.
Worldwide by 2014 there were 641 million obese people, compared with 105 million 40 years ago.
Click here to read the full report.