These 3 men claim they've reversed their biological age. Here are their daily routines.

• These people claim to have reversed their ages between five and 20 years.
• All three follow plant-based or vegan diets and exercise regularly.
• Bryan Johnson spends $2 million on keeping himself young through MRIs, blood tests, and supplements.

It's not just Peter Pan who wants to stay young forever.

There is a growing trend of biohackers and longevity experts who take extreme steps — and a small fortune — to keep themselves young and achieve their maximum lifespan.

They combine eating well, avoiding stress, exercising, waking up at 5 am, drinking matcha, having regular blood tests and MRIs scans, taking dozens of supplements every morning, and more, all in the name of hopefully shaving a few years off .

Insider looked at three men who claim to be experts at keeping their biological ages young to see how they did it.

David Sinclair

Harvard biologist and anti-aging researcher David Sinclair, 53, previously told Insider that his biological age is 10 years younger than his chronological age. He's calculated this based on science from his own startup, Tally Health, a platform that allows consumers to test their biological age and then make lifestyle factors to improve it.

Sinclair said that he drinks one to two green matcha teas every day that contain cancer-preventing molecules, and takes supplements that contain resveratrol, a chemical mainly found in red grapes. According to his team's research, this has been shown to extend the lifespan of organisms like yeast and worms — though other research has debunked the claim that this will work in humans. 

Sinclair also abstains from alcohol, eats a plant-based diet, and practices intermittent fasting "whenever possible" which he said has positive effects on his biological age. He also uses a standing desk to avoid sitting for long periods.

He emphasizes the importance of stress reduction and makes sure he "avoids jerks" to keep his stress levels low. He also sets aside periods of the day for quiet time to support healthy aging.

Dr. Mark Hyman

Dr. Mark Hyman, a longevity expert, is 63 but says that his biological age is two decades younger at 43.

Hyman previously told Insider that health problems that come with aging like achy joints, foggy thinking, and chronic illness can, in fact, be avoided or reversed.

"It's a treatable condition, as opposed to an inevitable decline," he said, and credits good nutrition and exercise to living both a long life and having a better quality of life.

His day starts at 6 am with 20 minutes of meditation — which is found to be beneficial to mental health and reduces stress — and coffee — which is linked to a lower risk of heart disease and dementia in some studies. 

Hyman then does resistance training to help with back pain and build muscle, followed by a 40-degree three-minute shower as he believes the cold temperature improves his metabolism and reduces inflammation.

Hyman follows a paleo and vegan diet, focused on mostly plant-based whole foods — which is good for the heart — and takes a series of supplements that he thinks maintain his energy and stress levels.

Bryan Johnson

A biotech entrepreneur, Bryan Johnson is 45 but says his biological age is actually eight years younger than that, Bloomberg previously reported.

And while he claims his heart is that of a 37-year-old, Johnson and his doctors told Bloomberg, his other organs are even younger: They claim he has the skin of a 28-year-old, and the lung capacity of an 18-year-old. 

They also claim he has the gum inflammation of a 17-year-old and the rate of nighttime erections of a teenager — because who wouldn't want to revert back to their pubescent self?

Hyman and Sinclair's lifestyles may seem a stretch, and Johnson follows similar principles: He maintains a vegan diet and exercises regularly — daily in fact.

But Johnson's lifestyle is one step further into the realm of outlandishness.

He gets up each day at 5 am and chugs down two dozen medicines and supplements including turmeric, zinc, metformin, and lithium.

Johnson also restricts his daily calories to the very exact number of 1,977 and has blood tests, MRIs, and colonoscopies each month to monitor and achieve his organ's young status.

This totals to about $2 million a year, Bloomberg reported — perhaps not achievable for the average Joe.