Are you sitting comfortably? Britons among laziest in Europe Britons are among the laziest people in Europe, according to new research that reveals only the Maltese and Serbs do less physical exercise. People's failure to take a brisk 30-minute walk, five days a week, causes up to ten per cent of cases of four major illnesses - heart disease, type-2 diabetes and breast and bowel cancer. Sedentary lifestyles were responsible for 5.3 million of the 57 million deaths globally in 2008, according to the study published online in medical journal The Lancet. Another paper in the same journal showed Britain has the third-highest number of inactive adults in Europe, 63 per cent, which is far worse than the US at 41 per cent. The new estimates suggest lack of exercise has become a contributor to the burden of disease and shortening of life expectancy similar to tobacco smoking or obesity. There is increasing concern the trend is getting worse with an "internet generation" who are spending most of their time sitting down. Researchers calculated by country and region how much the four diseases could theoretically be prevented in the population if all inactive people were to become sufficiently active. Some six per cent of heart disease cases are linked to physical inactivity, ranging from 3.2 per cent in south-east Asia to 7.8 per cent in the eastern Mediterranean. Dr I-Min Lee, of Brigham and Women's Hospital, Boston, 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 - 15 to 30 minutes a day of brisk walking - which brings substantial health benefits. The researchers also calculated the number of preventable deaths if activity increased by 10 per cent or 25 per cent - translating to some 533,000 and 1.3 million deaths potentially averted worldwide every year. Life expectancy of the world's population would rise by around 0.68 years if physical inactivity were eliminated. This is similar to the effect of eradicating smoking or obesity. Another study in the same journal showed about 1.5 billion people, and four in five adolescents, are failing to do the recommended amounts of physical activity - placing them at 20 to 30 per cent greater risk of heart disease, diabetes and some types of cancer. Researchers compared exercise patterns in adults over 15, from 122 countries, and in adolescents aged 13 to 15, from 105 countries. They found three in ten and eight in ten youngsters do not do enough - brisk walking for 30 minutes or more, five times a week, or vigorous exercise for 20 minutes, three times a week. Within Europe, the country with the greatest prevalence of inactive adults was Malta (71 per cent), followed by Serbia (68 per cent) and the UK (63 per cent). Study leader Dr Pedro Hallal, of the Federal University of Pelotas, in Brazil, said: "In most countries, inactivity rises with age and is higher in women than in men - 34 per cent vs 28 per cent. Inactivity is also increased in high-income countries.