People who exercise regularly are up to nine years younger, biologically, than sedentary people of the same chronological age, according to a new study by a team of British researchers.
You already knew that people who keep fit live longer than people who don't. Studies have shown they're less likely to have heart attacks, or to suffer from diabetes, cancer and other degenerative diseases. What makes this study by a team from Kings College in London different from all others that have come before it is that it may explain why.
"It helps prove what your doctor says all the time," said Dr. George Gabriel, a cardiologist at Allegheny General Hospital. "It's normal for your function to slow down. Exercise helps protect against the slowing-down mechanism."
The British researchers studied 2,400 twins. Their research focused on telomeres, the caps at the end of chromosomes, the structures that carry genes.
When we're young, our telomeres are long. But every time a cell divides, telomeres get shorter. When telomeres get too short, the cell can no longer divide. Cells die. Muscles weaken, skin wrinkles, eyesight and hearing fade.
Prof. Tim Spector and Dr. Lynn Cherkas of Kings College, and Prof. Abraham Aviv of the New Jersey Medical School found the telomeres in those who exercised vigorously were significantly longer than those in their twins who didn't. The difference was still significant even if the twin who exercised smoked or was overweight.
"These data suggest that the act of exercising may actually protect the body against the aging process," said Mr. Spector, who is a professor of genetic epidemiology. The study was published last month in the Archives of Internal Medicine.
"Overall, the difference in telomere length between the most active subjects and the inactive subjects corresponds to around nine years of aging," Dr. Cherkas said.
To maximize the anti-aging effect of exercise, you need to work out vigorously for at least three hours a week, the researchers said.
"It is not just walking around the block," said Prof. Spector. "It's really working up a sweat."
But people who work out at a moderate pace for an hour to an hour and a half a week can still reduce their biological age by as much as four years, the researchers said.
The study indicates that exercise "is actually a buffer against oxidative stress," said Dr. Moira Davenport, director of sports and emergency medicine for Allegheny General Hospital.
Oxidative stress is what damages and kills cells.
"Oxygen is essential to life itself. But it is also inherently dangerous to our existence. The same process that causes a cut apple to turn brown or iron to rust is the cause of all the chronic degenerative diseases we fear and even the aging process itself," said Dr. Ray Strand, a specialist in nutritional medicine.
"As oxygen is utilized within the furnace of the cell to create energy, occasionally a charged oxygen molecule is created, called a free radical," Dr. Strand said on his Web site, nutritional-medicine.net. "If this free radical is not readily neutralized by an antioxidant, it can go on to create more volatile free radicals, damage the cell wall, vessel wall, proteins, fats, and even the DNA nucleus of our cells."
Dr. Davenport said she was impressed with the British study, but cautioned that "it is a retrospective study. You can imagine how difficult it is to remember what you did 20 years ago. I can barely remember what I did last week."
Jack Kelly can be reached at firstname.lastname@example.org or 412-263-1476.