“Why did a gym instructor say that when we exercise our DNA gets “upgraded”? As far as I’m aware we are born with our DNA and exercise won’t change that!”
Both you and the gym instructor may be right. You certainly are – for we are all born with our own unique DNA and, fundamentally, that’s it – it won’t change. (Barring damage from radiation, carcinogenic chemicals, and the like.) So unless you choose to exercise on top of a nuclear reactor or something similarly crazy (!), doing exercise won’t rewrite a single letter of your genetic code.
However, there’s a relatively new branch of genetics called epigenetics that looks at inheritable changes to our DNA caused by environmental factors. Or, put simply: how life’s events get passed down to our children through our genes. In one famous study in Sweden (the Överkalix study), it was found that the effects of a famine over 100 years ago were felt not only by the people living at the time – but by their children and grandchildren. Their adversity was somehow ‘imprinted’ on their genetic code. It’s scary to think it, but how long you live could very well depend on what your parents, grandparents and perhaps even great-grandparents did when they were alive.
These ‘epigenetic’ changes are encoded in our DNA in the same way you might use a pen to underline an important word in a textbook – your scribble hasn’t changed the sentences, only extra meaning or emphasis. Similarly, sections of DNA can be activated and deactivated – turned on or turned off – mainly through chemical changes (one such process is called methylation which can change the way DNA is wrapped up in our cells).
We are now fairly certain that smoking, diet and major health adversities can be passed on epigenetically. With exercise, however, the evidence isn’t as clear cut. For one thing, exercise isn’t as dramatic as surviving a famine (although for ultra-endurance athletes, there may be some similarities). What we do have is some evidence for are short-term epigenetic changes on DNA after exercise. Whether these changes are beneficial, how long they last, or even whether they get passed on we just don’t yet know. At a stretch, it’s probably just about acceptable to say that the DNA has become ‘super-charged’ through exercise. Meaning that the gym instructor is right too.
Answer by Lewis Pike and Stuart Farrimond
Image: Superboy by jurek d., on Flickr