Lack of exercise is responsible for twice as many deaths as obesity, it says. Couch potatoes face greater danger from deadly cardiovascular problems like heart attacks and stroke as well as some cancers.
However, a 20-minute walk at a vigorous pace, or a cycle ride of the same duration, would move an individual from being classed as inactive to moderately inactive.
That small change alone would reduce their risk of early death by between 16 and 30 per cent, the Cambridge University researchers found.
Across the entire UK population, exercise from a young age would lead to an increase of nearly 12 months in average life expectancy. Individuals moving from total inactivity could gain many more extra years.
Even a small increase in physical activity each day like walking up escalators or using the stairs instead of the lift could provide significant health benefits.
Exercise for 20 minutes is recommended as a minimum and, where at all possible, more extended exercise should be carried out to achieve even greater benefits, the study says.
Professor Ulf Ekelund, head of the research team, said: “This is a simple message – just a small amount of physical activity each day could have substantial health benefits. Physical activity should be an important part of our daily life.”
This is a simple message – just a small amount of physical activity each day could have substantial health benefits
The researchers from Cambridge’s Medical Research Council Epidemiology Unit used the most recent available data to study 9.2 million deaths among European men and women.
Their report, published yesterday in the American Journal of Clinical Nutrition, estimated that 337,000 deaths were caused by obesity but more than double that number, 676,000, could be attributed to physical inactivity.
Research team member Professor Nick Wareham said: “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.”
He said the biggest killers are cardiovascular disease and types of cancer like cancer of the intestines which exercise can ward off.
“Brisk walking is just an example, as doing any exercise for the required time is just as good,” he said.
“The brisk walk is just a little bit quicker than normal, rather than window shopping. Even doing things like using the stairs will help.
“We used brisk walking as most people can do it and have a good relationship with it.
"Adults should aim to do at least 150 minutes of moderate intensity activity a week, carrying it out in sessions of 10 minutes or more.”
The findings are believed to be particularly important because of the scale and length of time carried out on follow-up analysis.
To measure the link between physical inactivity and premature death, researchers looked at data from 334,161 men and women across Europe, with just under a quarter of participants categorised as inactive.
Over a 12-year period it was found that the greatest reduction in risk of premature death came when people moved from the inactive and moderately inactive group into activity.
June Davison of the British Heart Foundation, said: “The results of this study are a clear reminder that being regularly physically active can reduce the risk of dying from coronary heart disease.”
The findings back up those from another recent study in which researchers at Cardiff University School of Medicine concluded that regular exercise, sensible eating, maintaining a healthy weight, minimal alcohol consumption and no smoking were the simple steps that guarantee longevity.