Britain has one of the most sedentary populations on earth, with almost twice the proportion of people defined as "inactive" as in neighbouring France, a study has shown.
On the eve of the London Olympics, global figures reveal that even the Americans put us to shame when it comes to taking exercise.
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In the UK, 63.3% of the population fails to meet recommended levels of physical activity, thereby increasing their risk of conditions such as heart disease, diabetes and cancer.
By comparison, 40.5% of US citizens are inactive, despite more than 30% of them being obese.
Britain has the third-highest proportion of inactive adults in Europe after Malta (71.9%) and Serbia (68.3%).
Few countries in the world have a greater inactivity prevalence, with the list topped by Swaziland (69%) and Saudi Arabia (68.8%).
Of the French population, 32.5% are inactive, while in the super-fit Netherlands just 18.2% of people are inactive.
In the Republic of Ireland, 53.2% of the population do insufficient exercise.
Researchers used World Health Organisation (WHO) survey data, collected by questionnaire, to compare 122 countries representing 89% of the world's population.
Inactivity was defined as not meeting any of three criteria: 30 minutes of moderate activity such as a brisk walk, at least five days a week; 20 minutes of vigorous activity at least three days a week; or an equivalent combination of the two.
The findings, part of a series of studies on physical activity published in The Lancet medical journal, suggest that, worldwide, roughly three out of every 10 adults aged 15 and over do too little exercise.
Study leader Dr Pedro Hallal, from the Federal University of Pelotas in Brazil, said: "Although the technical revolution has been of great benefit to many populations throughout the world, it has come at a major cost in terms of the contribution of physical inactivity to the worldwide epidemic of non-communicable diseases.
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"Societal trends are leading to less not more activity than previously, and with few exceptions, health professionals have been unable to mobilise governments and populations to take physical inactivity seriously as a public health issue."
The research also found that more than 80% of 13 to 15-year-olds around the world do not get the minimum recommended hour of moderate exercise a day.
A second study found that lack of physical activity leads to 6% to 10% of all cases of heart disease, type-2 diabetes, and breast and bowel cancer.
Globally, it was responsible for around 5.3m of the 57m deaths that occurred in 2008.
The contribution of insufficient exercise to disease and shortened lifespan was similar to that of smoking or obesity.
Researchers calculated the extent to which non-communicable diseases could be prevented if all a country's inactive population became active.
The estimates suggest that, worldwide, 6% of heart disease cases are linked to lack of exercise, ranging from 3.2% in south-east Asia to 7.8% in the eastern Mediterranean.
Low levels of physical activity are blamed for around 7% of type-2 diabetes cases, and 10% of breast and bowel cancer cases.
Average life expectancy worldwide would rise by around 0.68 years if no one was physically inactive, said the researchers. Eradicating smoking and obesity would achieve about the same result.
Study leader Dr I-Min Lee, from Harvard Medical School in Boston, US, said: "This summer we will admire the breathtaking feats of athletes competing in the 2012 Olympic Games.
"Although only the smallest fraction of the population will attain these heights, the overwhelming majority of us are able to be physically active at very modest levels, e.g. 15 to 30 minutes a day of brisk walking, which bring substantial health benefits."
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