Everyone knows that exercise is good for human health, but a new study has shown that it can actually alter DNA expression in our bodies.

The study, published in the journal PLOS Genetics, looked at fat cells in the bodies of 23 “slightly overweight,” but otherwise healthy middle-aged men. Though the men had not previously exercised, they were put on a regimen of spin and aerobics classes. Researchers then examined the genetic makeup of the men’s fat cells after six months. They found genetic changes in 7,000 different genes.

“Our study shows the positive effects of exercise, because the epigenetic pattern of genes that affect fat storage in the body changes”, said Charlotte Ling, a co-author of the study and an associate professor at the Lund University Diabetes Centre, where the research took place.

Though human genes do not change once inherited, different genes can be activated or deactivated by molecules in a process called “DNA methylation.” The study of this process is called epigenetics.

In addition to changes to their bodies’ fat storage, researchers found that exercise changed the DNA expression of genese linked to type 2 diabetes, suggesting that epigenetics may play a role in the disease.

“We found changes in [type 2 diabetes-linked] genes too, which suggests that altered DNA methylation as a result of physical activity could be one of the mechanisms of how these genes affect the risk of disease”, said Tina Rönn, lead author of the study and an associate researcher at Lund University.