To publish a book in January is to signal to the world that you hold the secret to miraculous self-improvement. Venture into a bookshop today and you’ll find brand new volumes on how to eat better, drink better, sleep better, prevent dementia, overcome anxiety, heal intergenerational trauma, and generally become invincible in the process. It is, quite frankly, exhausting.

And then there’s professor of immunology John Tregoning, who opens his new book Live Forever? by pointing out that you are definitely going to die. No matter what you do, he writes, time is guaranteed to defeat you. “It wants your heart to stop and your lungs to fail … and you to fade from the world, your only traces residing in the memories of others.” And a happy new year to you too, professor.

Over the next 430 pages Tregoning shows the reader how each and every organ can let them down. Maybe your heart will succumb to disease, or you’ll have a stroke. Maybe cancer will take you out, or your lungs starve you of oxygen. And don’t forget issues with your kidneys, or your liver, or your pancreas. Oh, or dementia. Whatever it is – assuming you’re lucky enough to avoid poison, serious accidents or infectious diseases – at some point your body will turn on you.

Tregoning points out that death is “the original zero-sum game”. There was a time when people mainly died of things they’d caught from other people. Science stopped this, so then people started dying of heart disease. Those figures are starting to improve, so now more people are dying of cancer. Maybe one day we’ll cure that too. But guess what? Something else will kill us instead. It always does. It is the bleakest of all subject matters. With this in mind, then, the most surprising thing about Live Forever? is just how delightful it is. This is a warm, charming and often laugh-out-loud funny book, and that is entirely down to Tregoning’s willingness to use himself as a guinea pig at every turn.

Organ by organ, he submits himself to a test, diagnostic tool, or so-called cure in the hope that his life will somehow be lengthened. He gets his genes sequenced, restricts his calories, goes cold-water swimming and embarks on a nightmarishly fibre-filled diet. The experiments annoy his family and colleagues, sporadically change the colour of his urine and often make him despair about the wellness industry as a whole. But do they work?

It might come as a disappointment to some that Professor Tregoning doesn’t reach any kind of groundbreaking conclusions here. There is no hidden secret to outpacing death, just a reinforcement of the fundamentals we knew anyway. Smoking is bad for you. Exercise is good for you. Avoid too much salt, alcohol and red meat. Stress and isolation won’t help, but sunscreen will. Also, if you’re a man, try to ejaculate at least 21 times a month. The latter advice mortifies Tregoning to such an extent that he has to hide it behind two separate warnings and a full pagebreak, but its effect on prostate cancer is undeniable.

Sadly, even relentless ejaculation won’t stop death. It’ll get you in the end. Maybe you’ll live into triple digits and die of plain old cellular wear and tear, although by that point all your friends will be dead, you’ll be heavily reliant on medication and your quality of life will probably suck. With that in mind, would it be better to smoke and drink and eat steak in the hope that a monumental heart attack will take you out without warning? Also no, because as Tregoning points out, those things are just as likely to contribute to diseases that will leave you staggeringly unwell for years and years. Death is less scary than decline, he says. That’s the thing we can hopefully learn to manage.

The beauty of Live Forever? is that it acknowledges the fix we’re all in, but manages to do so in a way that almost feels like a comfort. By taking care of ourselves and, crucially, by leading happy and fulfilling lives, Tregoning reassures us that we can still make a decent fist of a bad hand. We’re all headed for the grave, but he’s as good a person as any to lead us there.

• Live Forever?: A Curious Scientist’s Guide to Wellness, Ageing and Death by John S Tregoning is published by Oneworld (£18.99). To support the Guardian and Observer, order your copy at guardianbookshop.com. Delivery charges may apply.