Sorry, couch potatoes -- the verdict is in: People who exercise regularly do look at least a decade younger than those who don't.

A study by a team of international researchers found that half-an-hour of exercise daily can not only slow the ageing process but also makes a person appear 10 years younger than an obese person of the same age.

According to lead researcher Prof Tim Spector of the King's College, London [Images], "The US guidelines recommend that 30 minutes of moderate-intensity physical activity at least five days a week can have significant health benefits.

"Our results underscore the vital importance of these guidelines. They show that adults who partake in regular physical activity are biologically younger than sedentary individuals."

In fact, the researchers came to the conclusion after monitoring a group of over 2,000 twins -- they measured the length of the telomeres (which cap the chromosomes in cells and protect the same from damage) of the participants. The telemores shorten with age, meaning more damage occurs. The team found that people who were active had longer telomeres than those of the same age who were sedentary.

The researchers also noticed that the effect was such that those who did 199 minutes or more a week of moderate to vigorous exercise, such as running, tennis or aerobics, were found to be 10 years younger than those who did less than 15 minutes of moderate exercise, even after considering factors like weight and smoking.

"Our study, performed on a large cohort, indicates that differences in telomere length between active and inactive individuals cannot be explained by variations in genes, smoking, BMI and SES.

"A sedentary lifestyle appears to have an effect on telomere dynamics -- thus providing a powerful message that could be used by clinicians to promote the potentially anti-ageing effect of regular exercise," the British media quoted Prof Spector as saying.