Like many celebrities and entrepreneurs, 45-year-old US tech billionaire Bryan Johnson is trying to reverse the ageing process.

Spending an average of $US2 million a year on an anti-ageing regimen, Mr Johnson claims he ages slower than some children.

He said: “The pace my body accumulates ageing damage is less than the average 10-year-old.”

Many of Mr Johnson’s age-reversal methods are questionable, involve dodgy science, and have known side-effects.

Although you can’t stop the ageing process, and the gradual decline our bodies experience as we advance in years, there are some things we can all do – for free – to maintain our health as we age.

What does Mr Johnson do? And is it scientific?

Fasting

Mr Johnson reports fasting for 23 hours a day. He then eats one meal a day: 2250 calories of nutrient-dense food “customised” to his body’s needs.

Eating for time-restricted periods in the day can have a positive effect on how we metabolise nutrients, inflammation levels, hormonal regulation, and cardio-metabolic health, blood sugar, triglycerides, cholesterol, blood pressure, BMI and waist circumference.

However, a Spartan-like food intake can impair how our body responds to sugar, known as glucose tolerance.

And it’s not necessarily any more effective for weight maintenance than reducing calorie intake at each meal.

Large-scale, long-term human trials are needed to confirm the limited risk-benefit findings of fasting.

Acid peels

Mr Johnson has weekly acid peels that use a mild acid to exfoliate the skin to maintain a “youthful glow”.

But you cannot smooth sagging facial skin or remove deep scars or wrinkles. Acid peels also come with risks, including organ damage, infection, scarring and swelling.

Plasma infusions

Perhaps the most bizarre youth-inducing procedure Mr Johnson has attempted is receiving blood transfusions from his 17-year-old son, Talmage.

US biotech companies have explored plasma infusions to tackle age-related diseases in humans for decades. But there are no proven clinical benefits.

Side-effects from blood transfusions include blood-borne infections, fever and allergic reactions.

Plasma infusions have side-effects. Photo: Getty

Historical attempts to stay youthful

Humans have been experimenting with anti-ageing methods for centuries.

These have included all sorts of behavioural and lifestyle practices that are quirky, questionable and even sadistic.

Ancient practices included crocodile dung face masks, which the Greeks and Romans used to brighten their complexions.

Romans also used donkey milk and swan fat to minimise wrinkles, due to their acclaimed rejuvenating properties.

Cleopatra apparently took daily baths in sour donkey milk. To sustain this lavish habit, she had a herd of 700 donkeys.

Sour milk contains lactic acid, a naturally occurring alpha hydroxy acid (AHA) that exists in many modern-day exfoliants. So this idea was grounded in basic science, at least.

During the 16th and 17th century, ‘Countess Dracula’, aka Elizabeth Bathory, allegedly resorted to serial killing to quench her thirst for youthfulness, bathing in the blood of her young victims.

Cryotherapy

Fountain of youth fixations have inspired many contemporary anti-ageing trends. Exposure to cold is a firm favourite.

Some research suggests this could have benefits relating to longevity, by slowing cellular degeneration, stimulating collagen and elastin production, increasing the metabolism, and reducing inflammation.

Dutch motivational speaker Wim Hof includes cold water immersion as one of the three pillars of his Wim Hof Method to “increase mind-body connection”.

Athletes such as Cristiano Ronaldo use cryotherapy, exposing their bodies to extremely cold temperatures for two to four minutes to decrease the signs of ageing and enhance their general health.

However, the risks of cryotherapy include bone fractures, frostbite, nerve damage, bleeding, cramping, swelling and skin infections.

Ageing well

Two of the more mainstream anti-ageing methods that Mr Johnson recommends are the daily self-care habits of sleep and exercise.

He has a strict sleep schedule that involves retiring to bed at 8pm, with a one-hour wind-down in a darkened room.

Adults report poorer sleep quality and difficulty being able to sleep for long enough as they age.

Sleeping too much or too little is associated with a greater risk of obesity, heart disease and premature death.

Developing a regular sleep routine, reducing bedroom distractions such as mobile phones, and exercising regularly can all help to alleviate sleep problems.

Exercise, often cited as a wonder drug for healthy ageing, is something Mr Johnson takes very seriously.

He does a ‘Blueprint‘ workout that includes specially designed daily techniques, as well as high-intensity interval training sessions, hiking and playing sport.

From middle age onwards, we all need to exercise regularly, to increase our muscle mass, bone density, strength, endurance, co-ordination and balance.

One of the greatest health risks for older people is falling, which balance, flexibility, endurance and strength training can help reduce.

Physical activity can bring social benefits in older adults if undertaken in groups, and there are well-known mental health gains.

Small changes in sleep, diet (eating plenty of vegetables, fruit, whole grains, healthy fats, and enough protein), and exercise can support healthy ageing, reducing the chance of early death, and help us all to lead an active and independent life in our senior years.

Now that is something worth investing in.

Rachael Jefferson-Buchanan is lecturer in Human Movement Studies (Health and PE) and Creative Arts at Charles Sturt University.

This article was originally published on The Conversation.