An important distinction must be made between arresting the appearance of ageing and actually stopping the ageing process. Most of us are more focused on appearances because the evidence is out there to see. There's also a big difference between reversing the effects of ageing and simply extending lifespan. Western medicine has become particularly good at the latter over the past century or so but has never properly tackled the former.

The scientific name for the process of ageing is senescence: cellular senescence is when a cell loses its ability to divide, and organismal senescence is when an organism starts to respond less well to antagonists in its environment, for example becoming more prone to disease. In humans, the latter usually starts at about the age of 35. This happens in almost all living things, although there are exceptions - turtles, for example - leading to the idea that it might be preventable.

There are many theories about why ageing happens - evolutionary explanations, others based on viruses, accumulation of wear and tear at a cellular level, and even the body's immune system ganging up on it.

What we do know is that certain things hasten the process: smoking; radiation, mainly in the form of the sun's ultraviolet rays; fatty, sugary and processed food; and lack of exercise. Take care of those and half the battle is won - but that's not enough for many people, particularly youth-obsessed Hongkongers.

And so, new clinics offering preventative medicine and aesthetics services - anti-ageing one-stop shops, if you like - have sprung up to cater for our desire for youthful looks.

Once such clinic, launched in May, is Life Clinic in Central, an integrated health and vitality centre that takes a three-pronged approach to regaining youth: internal anti-ageing medicine, aesthetics and regenerative medicine. It was founded by Dr Stephen Chan, from University College London Medical School. His clinic's treatment packages include consultations with a physician, nutritionist and personal trainer or psychologist; testing of hormone levels, free radical damage, anti-oxidants, minerals and essential fatty acids; and three-month courses of personalised supplements and bio-identical hormones.

Medica Esthetica, in Wan Chai's Sun Hung Kai Centre, takes a similar approach to preventing ageing. Soft-launched last year, it caters to a select clientele that founder Tony Agra describes as very high-end. This is the new face of anti-ageing, with an interior that's more spa than clinic and a healthy dose of new-age spin: a recurring spiral pattern motif and a tree of Egyptian crystals in the reception area, among them.

Agra, 52, whose background is in logistics, became interested in clinical research and ended up running similar clinics in Las Vegas and Texas. He was attracted to Hong Kong because people here 'tend to say: 'I don't have to age - I'm not going to take this lying down.''

He stresses that, whatever treatments a patient may undertake, ultimately most of the fight against ageing is in their hands. Each client gets an individual programme focused on lifestyle as well as medical treatments. 'It's a two-way process,' he says. 'We can do our bit, but they need to take ownership.'

He does, however, offer a big helping hand. Vitamin shots, for example, are administered in an area known as the Infusion Cafe. Agra says injecting vitamins means they have a direct impact at a cellular level, rather than having to go through the digestive system first.

Their benefits are disputed, however: Dr John Yu, a specialist in dermatology at Matilda Medical Centre, says our bodies only need so many vitamins - 'the body will just secrete the rest'.

There's also chelation therapy, a practice used in cases of heavy metal poisoning to remove the offending metals from the body. Not only does Agra claim it's effective in combating the effects of ageing; he also says it takes just 20 minutes with the clinic's special machines, rather than the usual few hours.

'The moment you step out there [on the street], you breathe in methylmercury, arsenic and lead,' he says. But Yu says chelation therapy can remove too much calcium from the body, and also affect the heart because the body's electrolyte balance can be disturbed.

Medica Esthetica's key offering is bio-identical hormone optimisation, in line with the belief that we age because our hormones decline, rather than vice versa. Bio-identical hormones are identical in molecular structure to the hormones made by the body, but are synthesised from plant chemical extracts. 'It's never too early,' says Agra, who recommends women start the therapy at about age 28 and men at 35.

Some experts, however, say that such hormones offer little or no benefit, and the risks are high. In an editorial last year in the journal Aging Health, Dr Thomas Perls, an associate professor of medicine at Boston University School of Medicine, remarked: 'The terms bio-identical or all-natural, particularly in the case of the drugs prescribed by endocrinologists, misleadingly convey a sense of safety to the gullible customer. Arsenic is all-natural too, and it even has some medical uses, but it is anything but safe.'

Yu is likewise sceptical about other miracle cures. Sirolimus, or rapamycin, which is usually used to suppress organ rejection after transplants, was found in 2009 to extend the life expectancy of mice by up to 38 per cent - but because it's a powerful immunosuppressant, 'it will kill the patient before increasing their lifespan', he says.

The enzyme telomerase shows promise as a supplement - telomeres, which it affects, are regions of DNA sequences at the ends of chromosomes whose length may help measure biological age - but, Yu says, 'the only studies have been on mice. There's no study to suggest it'll work on humans.' Originally developed for the US space programme, anti-ageing light therapy uses amber, red and infrared LEDs to stimulate production of collagen and elastin. Yu says that this is just about the only anti-ageing treatment with a proven scientific basis, albeit the effect is obviously a purely cosmetic one.

Aubrey de Grey, a biomedical gerontologist and chief scientific officer at the non-profit California-based Sens (Strategies for Engineered Negligible Senescence) Foundation, predicts that in the future, people will go to their doctors for regular 'maintenance'. By then, this will include gene therapies, stem cell therapies, immune stimulation, and other advanced medical techniques.

'I'd say we have a 50/50 chance of bringing ageing under what I'd call a decisive level of medical control within the next 25 years or so,' de Grey said in an interview with Reuters recently.

But, even if all of it works, there's no substitute for a healthy lifestyle.

Take, for example, 67-year-old grandmother Eddie Brocklesby. A social worker who runs her own charity, the Englishwoman is also a marathoner and triathlete who has competed in numerous events and won her age group several times - and who didn't even take up regular exercise until 14 years ago, following the sudden death of her husband.

She doesn't use any anti-ageing treatments, and takes no supplements except glucosamine for joint strength. Instead, she goes through a punishing daily exercise routine, and eats a healthy diet including lots of vegetables, fruit and ground-up seeds.

'If a pill had all the benefits of two-and-a-half hours' exercise per week, a normal healthy diet with fruit and vegetables, and no smoking, it would make a bomb,' she says. Yu puts it more succinctly: 'There is no systemic medication that can arrest ageing,' he says.

Even Agra agrees that 'the final step to self-realisation is something that has to be taken alone'. With anti-ageing, as with everything else, there are no short-cuts, no magic bullets, and no substitute for living a healthy life.

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- projected value of anti-ageing products market in 2015 in billions of US dollars