A study on identical twins who did the same levels of activity as children, but developed different exercise habits as adults, has provided fascinating insights into the effects of exercise on health.

Twins are so valuable for research since they share both the same DNA and upbringing. Ten pairs of twin men in Finland, with different exercise habits – one active, one not – were studied over the course of three years.

Their endurance capacity, body composition and insulin sensitivity was measured, and their brains were scanned.

Sedentary twins were found to have lower endurance capacities, higher body fat percentages and signs of insulin resistance, signalling the onset of metabolic problems.

Active twins had significantly more grey matter than sedentary twins, especially in the area of motor control and coordination.

Dr Urho Kujala, a professor of sports and exercise medicine at the University of Jyvaskyla, who oversaw the study, said presumably these changes had all occurred in the last three years, since their exercise habits had changed. He said it underscores how rapidly and robustly exercising, or not, can affect health.

Another positive outcome of the study is that genetics and environment do not have to be destiny when it comes to exercise habits.