It’s a well-known fact that being a couch potato is no good for your health, but research has discovered that  lack of exercise may even shrink your brain. Scientists at Boston University School of Medicine analysed medical data from around 1,600 people over 20 years. Each participant undertook a fitness test on a treadmill in the late’70s and early ’80s, during which time they were aged between 31 and 49. The volunteers ran on the machine until they reached a certain heart rate, with those who were more fit taking longer to reach it than those who did little exercise.

Fast forward two decades later to between 1998 and 2001, when the participants underwent neurological tests and MRI brain scans. It was found that those who had lower fitness levels were more likely to have smaller brains after 20 years. On average, total brain volume shrank by around 0.2 per cent annually, with those less fit in their 30s and 40s’ brains shrinking faster. This is said to be because keeping fit reduces blood pressure, thus resulting in less strain on the brain. The brain getting smaller can lead to early cognitive decline, dementia and premature death, and experts believe a sedentary lifestyle accelerates a person’s ageing process.

Brains naturally shrink with age, but this detection suggests exercise levels control the rate at which it happens. “We found a direct correlation in our study between poor fitness and brain volume decades later, which indicates accelerated brain ageing,” study author Dr Nicole Spartano said of the findings, published in the Neurology journal. “While not yet studied on a large scale, these results suggest that fitness in middle age may be particularly important for the many millions of people around the world who already have evidence of heart disease.”

By Collen Taku Hanyani