As the world's oldest man, John Tinniswood, turns 112 today, many of us may wonder about the secret behind an exceptionally long life.

Mr Tinniswood from Merseyside has put his longevity down to fish and chips, while others have named sleeping and home cooking as secrets to getting past the 100-year-mark.

However, while the world's oldest people might believe they have all the answers, scientists warn that you should think twice before taking their advice.

From a daily shot of hard liquor to regular trips to the chippy, some of the advice from the world's oldest people might be useless or even bad for your health.

Professor Richard Faragher, an expert in the science of ageing from the University of Brighton, told MailOnline: 'It's probably not a good idea to adopt these guys' health tips.'

Many of the world's oldest people tend to attribute their long lives to a specific habit or lifestyle choice.

Spain's Maria Branyas Morera – who was the world's oldest person until her death earlier this month – put her longevity down to positivity, a good connection with family and nature as well as 'staying away from toxic people' and 'emotional stability'.

Others, such as John Tinniswood – the world's oldest man at 112 – suggest that diet may be a big factor in their prolonged good health.

Mr Tinniswood, who was born in Liverpool in 1912 and lives in Southport, became the world's oldest man in April and turns 112 today.

He has attributed his long life to having 'everything in moderation' and a daily serving of battered fish and chips.

The previous world's oldest man Juan Vicente Perez Mora, who died at 116, also suggested diet was a factor – citing his daily glass of aguardiente, a sugar cane liquor, as a key factor.

However, according the Professor Faragher, trying to follow the lifestyles of the world's oldest people might be useless, or at worst, actively harmful.

Experts are still not sure exactly why some people are able to live so long but Professor Faragher explains that there are two likely reasons which are not mutually exclusive.

The first theory is that people who live an extremely long time may be different at the genetic level.

Professor Faragher says the reason centenarians live so long is that they have stayed healthy throughout most of their lives.

For example, the family of Ms Morera have previously said the supercentenarian had experienced an almost unblemished health record.

Her daughter Rosa Moret, speaking to regional Catalan television in 2023, said: 'She has never gone to the hospital, she has never broken any bones, she is fine, she has no pain.'

The waters are muddied further by the second possible explanation for why people live so long – they are simply very lucky.

'The key thing about it is whether its fundamentally different genetics or they're the luckiest b**ger alive,' Professor Faragher added. 

When centenarians are asked about the secret to a long life, they tend to name certain life habits – whether it's eating fish and chips, believing in God, drinking strong liquor or getting eight hours of sleep. 

But it's not necessarily these habits that caused their longevity, as others have engaged in these habits too and not lived as long – something known as 'survivorship bias'. 

To put it another way, if someone lives to 112 and eats fish and chips every day, it is easy to assume that they live that long because they eat fish and chips.

But just because someone has a particular habit and lives a long time, there should be no reason to assume that one causes the other.

In fact, it may be the case that many of the world's oldest people live past 100 despite their lifestyle habits rather than because of them.

Interestingly, this is a view shared by John Tinniswood who said: 'You either live long or you live short and you can’t do much about it.'

Several centenarians have also been smokers, with one 112-year-old Nepali woman, Batuli Lamichhane, smoking 30 cigarettes a day.

This clearly flies in the face of population-wide studies about smoking and life expectancy so we shouldn't expect smoking to have caused Mrs Lamichhane's long life.

Overall, whether it is genetics, sheer luck, or a combination of both that has led to these people surviving for so long, Professor Faragher says you shouldn't follow their advice.

He explains: 'If they're genetically different, it's not going to do you any good and if they're phenomenally lucky, the chances are that you aren't.

'What you should probably do, if you're interested in staying healthy, is not follow the advice of centenarians.'

This means that there is not much point in drinking a glass of strong liquor every day since it probably won't help you live longer and may even make you less healthy.

The exception to that rule is when a centenarian's advice aligns with what we know about healthy life expectancy at the population level.

For instance when someone like the then 114-year-old Elizabeth Francis said to avoid alcohol, maintain friendships, and exercise regularly – this is still sound advice.

Ultimately, experts say the best way to add a few extra years to your life is to address the simple factors that affect your health like diet and exercise, rather than pursuing very specific advice.

Professor Faragher concludes: 'I think of myself as a down to Earth person, so my advice is always to do the basics first.

'Before people start wondering about what marvellous supplement they should take, knock off the curry and six pints of beer first of all.'