Going by this, Swan must be close to 22 years old. His hands are smooth and plumpish, his handshake is firm and strong.

I later learn there are multiple studies showing a relationship between the strength of your grip and a variety of conditions including premature death. Sure, it's more about how much muscle you have on the upper and lower parts of your body, rather than whether you can swing off the monkey bars. A firm handshake is not a clear indication of grip strength but it might prove something.

I do, however, sense some hesitation when I stick out a hand for that handshake. Swan, known as "one of Australia's most trusted doctors" has become something of a voice of reason during the COVID pandemic. His podcast Coronacast won a Walkley Award in 2020, he's called on regularly to comment on the current COVID trends, from vaccines to the latest figures. He's been a busy man. Should we be back to not shaking hands? There's so much I want to ask him.

But my first question is why are we so obsessed with youth?

Forget COVID for a little while, if we can (but we'll come back to it), today we're talking about his latest book So You Want to Live Younger Longer: The ultimate guide to longevity.

Why are we so obsessed by youth? I'm 55 (Swan is in his late 60s) and I'm proud to be 55. If I consider myself a (relatively) fit and healthy middle-aged person, shouldn't I be content?

"Yes, you should," he says. "But what I'm talking about is not getting to 55 and being decrepit in the body of a 75-year-old. Wouldn't you rather be in the body of a 45, 50 year old? As we live longer, you don't want to get to extreme old age and be falling apart."

And that's kind of the goal of the book. How can we get to extreme old age - and babies born today can expect to have a lifespan into their 90s - in the body and with the brain of someone much younger.

With his trademark attention to the science, touched by humour and anecdote, Swan looks at ways we can prolong our life. From the latest research, to pills, programs and diets, he outlines what might be helpful, and harmful, in the eternal quest for youth.

Some of the more interesting research he outlines concerns parabiosis, a process where people are transfused with the blood of a younger person in the hope of "rejuvenation".

"There might be something in this one, but it's not about the blood," he says.

"What happens when you're young, the cells in your body turnover at a faster rate ... they're born, they do their job, they die and are eliminated from the body.

"As you age, some of the cells don't die properly and the body doesn't get rid of them. They hang around like grumpy old neighbours who call the cops at 10 past 10 because there's still noise coming from your house. They exude misery, if you like, and that makes the tissue around them older, essentially the rubbish doesn't get thrown out."

But it all comes down to dilution. Tests, on humans and animals, who were given a saline solution via a drip, showed slight signs of rejuvenation.

"It's not a solution for aging, but there's some thinking that the processes of aging that lead to such things as Alzheimer's might be helped if we could clear out the harmful substances in a more systematic way."

Swan is quick to acknowledge there is no magic pill. Although there is a chapter entitled Which Pill and Why, outlining the pros and cons of such things as resveratrol, metformin and rapamycin.

Rapamycin is a substance found naturally in the soil on Easter Island; it's been found to switch off one of the master switches for ageing.

"While that might seem like a good thing, it's a bit like turning out the light in your kitchen by going to the fuse box and cutting the power to the whole house," he says. "It disrupts all kinds of things."

It also, if taken long term and in high doses, increases the risk of high blood sugars and diabetes, not to mention nasty infections of the immune system. There's still much more research that needs to be done on how supplements can prolong our youth.

So what can we do in the meantime? These are the important things for the bulk of us. What changes can I make to my everyday life to get more everydays?

"It might be boring but do the basics no matter what chronological age you are," he says.

"Smoking burnt plants, especially tobacco [and he throws vaping in here too], high blood pressure, raised blood fats, lack of physical activity and being overweight or obese all speed up biological aging."

There's basic stuff you need to do. Quit smoking, get your high blood pressure and cholesterol levels down, your body mass index too. Have all the health screenings done for cancer and the like. Eat a diverse Mediterranean-based diet, get regular exercise, create an occasional calorie gap where you're eating less than you're burning.

"And know what people in your family have died of and at what age, the younger you find out the better. If there's a pattern in your family of people getting heart disease or cancer under 60 then perhaps consider genetic counselling. It could save your life if you screen for cancers you could be at risk of."

It also helps to look at the lives of those people who've lived a long time. Does it come down to good genes?

"Fifty years ago living to 100 was a genetic abnormality. That's changed. It still helps if we're looking at the extremes, say living to 105, 110, but people are living to 100 now because of the life they've lived, the choices they've made.

"If we look at people who live to 100, they haven't had high blood pressure, they've not smoked, or given it up early, they're not too fat, not too thin ... men are usually married but women are not."

It's important also to have social connections, intimacy and positive relationships.

"There's also evidence that centenarians have a way of being in the world where they just get over stuff. It's not that they don't have bad things happening to them but they get over it. Long-term large studies have found the more optimistic you are, the longer you live."

Is it ever too late to start making changes?

"You will gain most the younger you start but it's never too late," he says.

In your 20s, pick up some good habits: don't smoke, exercise 45 minutes to an hour most days of the week, and limit screen time after dark to get your circadian rhythm into shape.

In your 30s and 40s, find a GP you like and stick with them, don't sit on symptoms like bleeding and bruising or new onset of pain just because you're young.

At 50, get breast and bowel screening done, keep eating a diverse diet, keep your abdominal fat as low as possible.

If you've made it to 60 or 70, even 80 or 90, keep up that diverse diet and exercise, learning new skills can deepen neural networks, get as much quality sleep as you can, stay social.

There's an end note to the book which might make you wonder why you'd be keen to live as long as you can. Swan talks about the effect pandemics, overpopulation, climate change and other environmental disruptions all have on our life expectancy.

"If there's one thing that we all found scary during the pandemic is the acknowledgement that life is fragile," he says.

"COVID-19 will have set back average life expectancy globally by one or two years. Future pandemics caused by new organisms from animals will do the same again and again.

"When the Soviet Union fell apart in the late 1980s, life expectancy went backwards, it's only just recovered but I suspect it may well go backwards again given the current situation.

"In the United States life expectancy is going backwards due to obesity, and here in Australia it may well do the same."

I'm surprised Swan, the proud Glaswegian, hasn't heard of Queen's song Who Wants to Live Forever, made popular, in my mind at least, from its use in the 1986 film Highlander. Christopher Lambert played Connor MacLeod, a Scot who's an immortal warrior and remains so unless he is beheaded. Sure, it wasn't very well reviewed, but something stuck in my mind about how terrible it would be to live forever if all your social connections were dead or dying. "Who wants to live forever, oh, oo woh, when love must die."

Does Swan want to live forever? He exercises almost every day, combining strength and aerobic fitness, eats red meat maybe once a week, maintains a diverse diet based on white meat and vegetables. He admits to a few guilty pleasures: tries not to drink too much but sometimes fails; he loves the trays of hors d'oeuvres at functions; he had some chocolate before he came downstairs for our interview.

"I don't want to live forever but I do want to hang around for as long as it's feasible," he says.

We've made it a whole lot easier for you to have your say. Our new comment platform requires only one log-in to access articles and to join the discussion on The Canberra Times website. Find out how to register so you can enjoy civil, friendly and engaging discussions. See our moderation policy here.