A brisk 30-minute walk six days a week is enough to trim waistlines and cut the risk of metabolic syndrome - an increasingly common condition that is linked to obesity and a sedentary lifestyle, a new study indicates.

"Our study shows that you'll benefit even if you don't make any dietary changes," study leader Johanna Johnson, a clinical researcher at Duke University Medical Center, Durham, North Carolina, said in a statement.

It's estimated that about one quarter of all US adults have metabolic syndrome - a cluster of risk factors that raise the odds of developing heart disease, diabetes and stroke. To be diagnosed with metabolic syndrome, a person must have at least three of these five risk factors - a large waistline, high blood pressure, high levels of harmful triglycerides, low levels of "good" HDL cholesterol, and high blood sugar - and according to many studies, a growing number of people have these problems.

The new findings stem from the STRRIDE study - an acronym for Studies of a Targeted Risk Reduction Intervention through Defined Exercise - in which investigators examined the effects of varying amounts and intensity of exercise on 171 middle-aged, overweight men and women.

Before exercising regularly, 41 percent of the study subjects met the criteria for metabolic syndrome. At the end of the 8-month exercise program, only 27 percent did.

"That's a significant decline in prevalence," says Johnson. "It's also encouraging news for sedentary, middle-aged adults who want to improve their health. It means they don't have to go out running four or five days a week; they can get significant health benefits by simply walking around the neighborhood after dinner every night."

The results of the STRRIDE study, which was funded by the National Institutes of Health, appear in the American Journal of Cardiology this month.

People in the study who exercised the least - walking 30 minutes six days a week or the equivalent of about 17 km per week - gained significant benefit, while those who exercised the most, jogging 27 km per week, gained slightly more benefit in terms of lowered metabolic syndrome scores.

People who did a short period of very vigorous exercise didn't improve their metabolic syndrome scores as much as those who performed less intense exercise for a longer period, the researchers found.

This suggests, they say, that there's more value in doing moderate intensity exercise every day rather than more intense activity just a few days a week.

All of the exercisers lost size around their waistline over the 8-month study period, whereas the inactive control group gained an average of about one pound and a half-inch around the waist. "That may not sound like much, but that's just 6 months. Over a decade, that's an additional 9 kg and 25.4 cm at the belt line," notes Duke cardiologist Dr William Kraus, the study's principal investigator.

"The results of our study," he adds, "underscore what we have known for a long time. Some exercise is better than none, more exercise is generally better than less, and no exercise can be disastrous."

(Agencies via China Daily December 26, 2007)