A lack of exercise may be twice as likely to lead you to an early death than being obese, a new study by University of Cambridge scientists suggests.

The researched looked at 334,161 Europeans with an average age of 50, and found that those who engaged in a little bit of exercise - even just a brisk 20-minute-walk daily - were 16 to 30 percent less likely to die prematurely than people who were sedentary.

This small amount of activity had the biggest life-boosting benefit on people who were a healthy weight, but even those who were obese lived longer if they were walking daily.

"This is a simple message: just a small amount of physical activity each day could have substantial health benefits for people who are physically inactive," said Ulf Ekelund, who led the study, in a press release.

According to the most recently available data, the researchers calculate that this means that out of the 9.2 million European deaths each year, around 676,000 could be attributed to being physically inactive. Around half of that, 337,000, could be attributed to obesity.

The study also showed that waist circumference had a similar impact on early death to exercise levels.

To work out what was linked to people dying prematurely, the study measured the height, weight, exercise level and waist circumference of the 334,161 participants between 1992 and 2000. They then followed up with each participant over the next 12 years. During that time, 21,438 of their volunteers had died.

The one thing that the majority of those who were still alive in common? They weren't completely inactive (surprisingly, almost a quarter of the participants were - they admitted to having sedentary jobs and then doing no exercise in their free time). 

Even when taking into account how much alcohol each person drank, whether they smoked, their age, sex and education level, the research showed that just burning between 90 and 110 calories a day, which can be achieved by a quick 20-minute walk, reduced the chance of dying from any cause.

The results have now been published in an open access paper in the American Journal of Clinical Exercise.

Of course, even though 20 minutes is useful, the researchers still believe that people should be doing much more to receive further health benefits. But this basic level does provide a very simple message - walking each day can help save your life, even more so than losing weight.

"Helping people to lose weight can be a real challenge," said Nick Wareham the director of the Cambridge Medical Research Council, which ran the study, in a release. "And whilst we should continue to aim at reducing population levels of obesity, public health interventions that encourage people to make small but achievable changes in physical activity can have significant health benefits and may be easier to achieve and maintain."