The fountain of youth may be at the gym. A new study described in The New York Times suggests that exercise not only helps prevent skin aging, but also may be able to reverse skin aging in older adults who begin exercising later in life.

With increasing age, skin tends to become wrinkled and saggy due to changes within the layers of the skin. The top layer of the skin usually tends to thicken and dry out starting around age 40. In addition, the supporting layers below tend to thin, losing elasticity and starting to cause sagging. Add the effects of years of sun exposure to these age-related changes, and you get wrinkly, old-looking skin.

Following a prior study that showed that mice who exercised were able to age more slowly, scientists at McMaster University in Ontario decided to test the theory that exercise could slow or reverse aging in people. They took 29 volunteers between the ages of 20 and 84. Half of them did at least three hours of moderate to vigorous activity a week, while the others exercised less than an hour a week. When the researchers took skin samples from an area not exposed to the sun, they found that men and women over age 40 who exercised frequently had thinner, healthier outer layers of skin and thicker middle layers, making their skin microscopically resemble the skin of someone decades younger.

To further test their hypothesis, the researchers then asked a group of sedentary subjects over the age of 65 to begin exercising. These volunteers worked out twice a week for 30 minutes by jogging or cycling, attaining about 65% or more of their maximum aerobic capacity. The volunteers did not make other major lifestyle changes apart from exercise. After three months, the scientists compared skin samples taken before and after the exercise regimen. They found that the skin looked markedly different, with the second sample resembling the skin of someone who was between 20 and 40 years old.

The researchers are not sure how or why exercise appears to reverse skin aging, but they did find that exercise increased the levels of a particular substance generated by muscle, called IL-15. They believe this substance may be responsible for the effects they observed. However, further study is required to see if their results can be replicated on a larger scale and to try to explain exactly how exercise may exert these anti-aging effects.