Identical twins: same body, same brain, same everything ... right?
Well, not exactly. Apparently, the similarity between identical twins depends not only on the body they're born with, but also how they treat that body.
Identical twins in Finland who shared the same sports and other physical activities as children but different exercise habits as adults soon developed quite different bodies and brains, according to a new study summarized by The New York Times. The study attempts to demonstrate the extent to which exercise shapes our health, even in people who have identical genes and nurturing.
Scientists at the University of Jyvaskyla and other Finnish institutions turned to Finland's extensive FinnTwin16 database, which contained twins' answers to questionnaires about their health and medical conditions, beginning when the pairs were 16 and repeated every few years afterward.
The researchers wanted to focus specifically on identical twins in their early- to mid-20s whose exercise habits had gone in complete opposite directions after leaving home — which was pretty difficult to find.
But eventually, the researchers honed in on 10 pairs of male identical twins, one of whom regularly exercised, while the other did not. According their questionnaires, the differences in their exercise routines had mostly started within the past three years.
The scientists measured each young man's endurance capacity, body composition, and insulin sensitivity to determine their fitness and metabolic health. They also scanned each twin's brain.
This is what they found, according to the Times:
It turned out that these genetically identical twins looked surprisingly different beneath the skin and skull. The sedentary twins had lower endurance capacities, higher body fat percentages, and signs of insulin resistance, signaling the onset of metabolic problems. (Interestingly, the twins tended to have very similar diets, whatever their workout routines, so food choices were unlikely to have contributed to health differences.)
The twins' brains also were unalike. The active twins had significantly more grey matter than the sedentary twins, especially in areas of the brain involved in motor control and coordination.
Co-author Dr. Urho Kujala said he believes that this is strong evidence that the differences in the twin's exercise habits caused the differences in their bodies. Other than that, he said, the findings also point out that genetics and environment "do not have to be" destiny when it comes to exercise habits.
So what does this mean for the rest of us? We don't need to let DNA control our lives entirely. Even if the input from both our genes and upbringing urges us to be couch potatoes, we can push ourselves to move more, and, based on this study, quickly and dramatically improve the condition of both our minds and bodies.
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