HABITS: Solitary, impulsive
APPETITES: Food, work, sex
EXERCISE: None
ATTITUDE: Optimistic

We think science can tell us almost anything: we live in an age when experts can say how a mummy died 4,000 years ago, or name the Yorkshire Ripper hoaxer in hours by taking DNA from an envelope licked in 1979. We have MRI scans, genetic and hormonal testing, and tiny cameras that can explore inside us. What can science reveal to us? And how much would you really want to know?

Tucked away in an up-market shopping mall in Scottsdale, Arizona, is a research institute where you can walk in off the street and get yourself tested to the extreme. This is the Kronos Optimal Health Centre, which asks its clients for seven tubes of blood before a two-day programme of physical testing. Then, in Britain, there are experts in psychological testing who will describe your personality with frightening accuracy; people who can divine what you eat and where you live, from a strand of hair; a professor of eye surgery who was able to study my tears and see what I’d had for lunch the previous day. How much do these people know?

This is the exercise, then. Take one Adam, one Eve. Each outwardly healthy, each old enough to harbour hidden killers. Ariel Leve is 38; I turned 46 this month. She is a vegetarian New Yorker who is anxious about her health; I’m a careless Englishman who knows every dietary pronouncement and follows none. We invited scientists on two continents to tell us whatever they can, with life-changing results.

In Britain, we have a simple model of health care: we wait for disease to show, then we treat it. What doctors do not find, they do not have to deal with until there are symptoms. Take eye examinations. The eye is the only place in the body where nerves and blood vessels are on display, which means it has a story to tell about health. In Britain, eye tests are done mainly on the high street and the motive is to sell spectacles, not detect disease. In middle age, I still have good vision; “super-vision”, in fact. Thus I have never had a proper eye examination. That’s Britain, and it’s why our elderly have higher rates of eye disease than in other developed nations.

Private health screening tends to give broad advice on diet and lifestyle. Yet scientific advances in the last decade have introduced real precision, allowing the purchase of knowledge that was once the property of fate. Women can find out how many eggs are left in their ovaries in the comfort of their bathroom, while men can test their sperm count without stepping out of the house. The new era raises the exciting prospect of individual care – of preventive treatment tailored to your actual make-up, with health resources used efficiently for the first time.

“There is little doubt that in 50 years’ time a genetic profile will be part of your health check,” says Kay Davies, an Oxford professor of anatomy. “It may not tell you how long you will live, because of the large environmental component, but it will say how to minimise any risks for heart disease, Alzheimer’s and so on.”

In half a century? We want this now. And guess what – you can have a version of it immediately.

Unlike Ariel, who approached this exercise with respect for the tests and dread of the results, I was cheerfully sceptical. So what if I turned out to have the genetic markers for cancer or heart disease? We’re such complex beings that genes are just part of the story. Intimate flirting with science holds no fear. Friends asked if we were going to receive counselling with the findings.

I don’t need counselling, I thought: I would rely instead on a study of 678 nuns in the Journal of Personality and Social Psychology, who were asked in the 1980s to write self-portraits. The women who were positive about themselves tended to live significantly longer. I am an optimist, and how is science going to factor in that?

At Kronos, medicine is based on risk assessment: it tries to do now what our Oxford professor sees as the future. At the frontier of commercial science, the tests are familiar but more sophisticated. When you run on a treadmill for a health insurer in Britain, electrodes monitor how the heart performs under stress. At Kronos, you also wear a face mask to measure how efficiently you process oxygen. In Britain, the body mass index is indicative of the content of fat in your body; in Arizona a full body scan shows where this fat is. The work yields more statistics than a person needs: the report on my screening runs to 257 pages.

I now know my left arm is 20.7% fat, and so is my right. I can see not only the levels of “good” cholesterol and bad in my blood, but the precise make-up of these fats, and the fact that my level of coenzyme Q10, “a terrific antioxidant” that is made in the body and can be found in a variety of foods, is barely acceptable at 0.591. My bones are so dense they are almost off the scale, but feeble habits mean my upper-body muscular strength is poor. My biological age is 53, seven years older than my chronological age. I know from a brain scan that I have mild diffuse cortical atrophy. This means my brain has shrunk. It is common with age and moderate drinking. So what?