It's pretty easy for us to all agree that going for a run, a walk, or a bike ride improves our health and reduces the risk of certain diseases. The data supports this. But how does this happen? What is going on in out bodies that converts exercise into a healthier you?
Turns out that, at least in part, there are changes happening at the level of the DNA. Numerous studies now show that exercise changes the epigenetic profile of our genes, and these changes correlate with improved health and fitness.
Although all the cells in your body have the same DNA sequence, which genes are active and which are shut off depends on the epigenetic profile of each cell type. Moreover, the time at which these genes are active or inactive depends on specific environmental cues. Your body is a spatiotemporal symphony of gene expression. Exercise puts the music in tune.
Epigenetic marks sit on top of the DNA. Think of it as molecular dust. As this dust settles on parts of your genome, it makes it difficult for other signaling molecules to cue genes to make proteins. This pattern of molecular dust can be changed by a number of negative factors (smoking, obesity, aging) and positive ones (diet and exercise). Depending on which genes are affected, these changes can increase or decrease our risk for disease.
Scientists know that methylation patterns change in response to lifestyle. Eating certain diets or being exposed to pollutants, for instance, can change methylation patterns on some of the genes in our DNA and affect what proteins those genes express. Depending on which genes are involved, it may also affect our health and risk for disease.
There have been several recent studies that have established changes in DNA methylation are associated with exercise. However, it is difficult studying freely moving humans and, subsequently, it difficult knowing exactly what caused the epigenetic changes - was it exercise, diet, or some other change in behavior?
To address this question, one study from the Karolinska Institute invited 23 men and women to their lab to exercise just one leg for 45 minutes, 4 times per week. The other leg they left unexercised. The idea was both legs would be subject to epigenetic changes from diet and other behaviors, but the effects of exercise would be isolated to the one leg.
After 3 months of training, the exercised leg was certainly stronger than the other leg. No shocker there. However, they also found more than 5000 sites on the genome were epigenetically different between the two legs from muscle biopsies. Many of the gene that saw epigenetic changes are involved in metabolism, insulin response, and inflammation. Pretty strong evidence for epigenetics affecting the health of our bodies.
Okay, fine. Exercise changes the epigenome of muscle cells. But what about other cells in the body?
In a 2015 paper, an Australian research group looked at epigenetic changes in sperm cells. 24 men were split into two groups - one group engaged in 3 months of sprint interval training, the other group did nothing. The investigators collected sperm samples at the start of the study and at the end and looked for epigenetic changes in the sperm.
They found that exercise training significantly changed the epigenome of the sperm. What was particularly striking was that they found increased methylation (suggestive of gene silencing) at regions associated with debilitating diseases such as schizophrenia, Parkinson’s disease, cervical cancer, leukemia and autism. Many of these methylation changes occurred in paternally imprinted genes that escape DNA methylation reprogramming after fertilization, suggesting these exercise-induced changes may be heritable across generations!
Another interesting finding is that they found global decrease in methylation after exercise training. In many different tissue types, aging is associated with increased DNA methylation. Perhaps exercise could serve as a method for counteracting the effects of aging? An intriguing idea.
The evidence for exercise-related changes in your epigenome is strong. Now you can feel confident that you're not only going to look and feel better, but your DNA will work bettter, too!