Fast walking and jogging halve development of heart disease and stroke risk factors

But an hour's walk every day makes no difference: Intensity rather than duration is what counts

The findings indicate that it is the intensity, rather than the duration, of exercise that counts in combating the impact of metabolic syndrome - a combination of factors, including midriff bulge, high blood pressure, insulin resistance, higher than normal levels of blood glucose and abnormal blood fat levels - say the authors.

Genes, diet, and lack of exercise are thought to be implicated in the development of the syndrome, which is conducive to inflammation and blood thickening.

The authors base their findings on more than 10,000 Danish adults, between the ages of 21 and 98, who were initially assessed in 1991-94 and then monitored for up to 10 years. All the participants were quizzed on the amount of physical activity they did, which was categorised according to intensity and duration.

At the initial assessment, around one in five (20.7%) women and just over one in four (27.3%) men had metabolic syndrome. Prevalence was closely linked to physical activity level.

Among the women, almost one in three of those who had a sedentary lifestyle had the syndrome whereas only one in 10 of those who were very physically active had it. Among men, the equivalent proportions were just under 37% and just under 14%

Of the remaining 6,088 participants without metabolic syndrome, just under two thirds (3,992) completed the fourth and final survey and assessment, by which point one in seven (15.4%; 585) had developed it.

Again, the prevalence was higher among those leading a sedentary lifestyle, with almost one in five (19.4%) affected compared with around one in nine (11.8%) of those who were very physically active.

It was not only the amount of exercise, but also the intensity which helped curb the likelihood of developing the syndrome.

After taking account of factors likely to influence the results, fast walking speed halved the risk, while jogging cut the risk by 40 per cent. But going for an hour's walk every day made no difference.

"Our results confirm the role of physical activity in reducing [metabolic syndrome] risk and suggest that intensity rather than volume of physical activity is important," conclude the authors.