By comparing twins — one fit and another unfit — Finnish researchers have proven the powerful impact of exercise on the body. They found 10 pairs of male identical twins in which one exercised regularly and the other didn’t. Though genetically identical, the unfit twins had higher body fat, lower endurance and showed signs of likely insulin resistance and metabolic problems. But that’s not all. The fit twins had far more grey matter in the brain, particularly in areas of motor control and co-ordination. Case closed.