For the longest time, people thought that the best way to avoid dementia is to eat a healthy diet and to stop smoking. However, new research revealed that the best way to combat dementia is to exercise.

Joseph Firth from the Western Sydney University said in his study that being active several times a week actually helps maintain the size of the region of the brain associated with memory, according to the Daily Mail. The region, known as the hippocampus, is the first to deteriorate when patients develop Alzheimer's disease.

"When you exercise you produce a chemical called brain-derived neurotrophic factor (BDNF), which may help to prevent age-related decline by reducing the deterioration of the brain," he said. "In other words, exercise can be seen as a maintenance programme for the brain."

Firth conducted 14 studies among 737 participants aged 24 to 76, with an average age of 66. The participants were classified as healthy, those with Alzheimer's, and people with mental health problems such as depression and schizophrenia.

He scanned the brains of the participants before and after completing exercise, which were done twice or five times a week ranging from three months to two years. The exercise could be as simple as walking or running on the treadmill, or other forms of aerobic exercise.

The results, according to Firth, were amazing as he found that exercise significantly increased the left side of the brain's hippocampus. "Our data showed that, rather than actually increasing the size of the hippocampus per se, the main 'brain benefits' are due to exercise slowing down the deterioration in brain size," he said.

Firth's findings are backed up by a study conducted by Dorina Cadar, a research associate in the department of behavioral health science at the University College of London.

Cadar told TIME that education and exercise really help prevent dementia. "We should really look at not just a single individual factor but a combination of factors: exercise, a healthy diet, having contact with friends and relatives," she said. "Together, they seem to help people in older age."