National Geographic fellow and author Dan Buettner has shared the 'one thing' you can do to improve your chances of reaching 100 years old.

The explorer and educator, 63, recently took to Instagram to tell his followers to get 'better friends' since this is the way that you're going to make lasting changes to your life. 

Buettner advised: "If you really want to live until you're 100, you need better friends because, at the end of the day, the only way you're going to live a long time is through long-lasting changes to your life.

"Diets and exercise programs generally don't live a long time, friends tend to be long-lasting adventures, and they have measurable impacts on your health behaviours for the long run".

Dan Buettner says 'you need better friends' for a longer life

The author suggested that people should "re-curate" their "immediate social circle".

The expert continued: "Those three friends who you count on when you're having a bad day or people with whom you can have a meaningful conversation.

"Those people are going to have a measurable and long-term impact on how active you are and what you eat".

He concluded with a warning: "It's counter-intuitive, nobody can make any money off you but be very careful about who you let in the room."

Buettner has become well known for his research into five "blue" zones across the world where inhabitants regularly live well into their old age.

The explorer regularly shares lifestyle advice on his platform based on his studies of these zones including tips on diet and exercise to promote life longevity.

Recently, the expert highlighted the benefits of drinking at least three cups of green tea a day.

Speaking on Jay Shetty's Podcast ON Purpose, Buettner said: "Seven is ideal but as little as three cups of Green tea a day is associated with four extra years of healthy life expectancy".

The expert admitted that we currently don't know why this is but he suggested it could be due to the antioxidants.

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The author elaborated: "There's probably 1500 in Green tea, we don't know for sure.

"Green tea has been around for a long time and it is consumed daily in volume by at least two of these blue zones.

"It's one of these things of rather than turn to the superfood or the super beverage - why not drink from what we have learned from our ancestors who've achieved the outcomes we want which is a long and healthy life?"