What is the importance of exercise if you are young, fit and healthy? Researchers in Finland have tried to answer this question by studying male identical twins. As these brothers are identical at the gene sequence level, any difference should be due to lifestyle factors.
They recruited 10 healthy male identical twins between 32 and 36 years old, of which only one brother had been exercising regularly for the last three years. They then measured their body weight and fat percentages, assessed their glucose levels and insulin sensitivity, and calculated the volume of their brains’ grey matter using magnetic resonance imaging.
The active twins had a higher VO2max and less visceral fat than their sedentary brothers, even though their body weight was not that different. Their glucose levels were lower and their insulin sensitivity* was higher. They also had a higher volume of grey matter in those areas associated with motor control.
The researchers concluded that even among healthy young adults exercise makes a difference. This is important, as lower fitness levels, more visceral fat and poor glucose metabolism are associated with chronic diseases later in life. Obviously, the negative effects of being sedentary begin early!
You might wonder if you have taken up exercise because you have a more favourable genetic profile than sedentary people. If so, you would be healthier whatever you do. This study suggests that this is not the case and that exercise makes a real difference, since identical twins should have the same genetic profile. This does not mean that genes do not matter. They are very important indeed, but you can influence them by your lifestyle.
This is only a small study. It would be great to confirm it with larger ones, but it must be very difficult to find a large group of identical twins of the same sex and age group with different exercise habits.
* Insulin sensitivity = how sensitive the body is to insulin stimulation. Low sensitivity is associated with higher risk of diabetes type 2.
Rottensteiner M, Leskinen T, Niskanen E et al. Physical acivity, fitness, glucose homeostasis, and brain morphology in twins. Med Sci Sports Exerc. 2015; 47(3): 509-518.
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