Former Labour health minister Lord Darzi has called for people to adopt a "use it or lose it" attitude to their brain to protect against dementia.
Writing in The Telegraph, Lord Darzi said people should act now to change their diet and exercise habits and stimulate their mental capacity using puzzles.
"At an individual level we need to look after our brains - sharpen those chess skills, pick up that crossword and solve that puzzle," he suggests.
"Eating a healthy diet, avoiding obesity and getting plenty of exercise are all important to brain health because what is good for our hearts is also good for our heads."
The former health minister's comments came as a working group prepared to publish a study that suggests three million cases of dementia could be avoided in Britain by 2040 by lifestyle changes.
In February, the findings of a major global report into dementia will be presented at the World Innovation Summit for Health in Doha.
The study states that more than 80,000 people a year could be saved from dementia by lifestyle changes to protect the brain.
Taking action early in life could help to prevent such degenerative diseases, as there is increasing evidence that deterioration of the brain starts in the 40s.
Adopting a healthy diet and exercise could help to reduce blood pressure in midlife and therefore protect against dementia.
Type two diabetes, which is also linked to weight gain, is identified as the next major cause of neurodegeneration and is responsible for more than one third of cases of dementia.
In addition, 4,000 cases a year result from obesity and inactivity - twice as many as those associated with smoking.
The report presents a study of 1,200 people in their 60s and 70s in Finland, half of whom changed their diet, managed their heart health, engaged in more social activity and embarked on brain training.
Those who made the changes had better general health and achieved better results in tests of memory, planning, judgment, problem-solving, and speed of cognitive processing.
Read more about Barchester's dementia care homes.