Know thyself: the Quantified Self devotees who live by numbers

A large man in an orange shirt is hopping up and down on one leg at the front of the hall explaining how the exercises had no effect on his sleep patterns. A researcher from Liverpool tells how he learned about the effects on his body of calorie-laden sandwiches, drinking sessions and Christmas feasting by monitoring his heart rate non-stop for a year. Elsewhere speakers with Parkinson's disease, chronic social anxiety and back problems explain how tracking their personal data helped ease their symptoms.

Welcome to the sometimes wacky and often intriguing world of the Quantified Self, an eclectic band of hackers, geeks, fitness freaks, patients and early adopters that, from its birth in California in 2008, has grown into a global movement of more than 5,000 members in 11 countries. Last weekend 260 delegates gathered in Amsterdam to share their experiences at the first Quantified Self Europe conference.

In science, politics, medicine and many other spheres, data is routinely collected to fine-tune performance. The realm that has so far evaded the cult of numbers is our personal lives. The idea of someone keeping spreadsheets of data on their mood, health, diet, physical location, personal productivity and sleep patterns might in the past have attracted a certain amount of scorn.

That is changing and fast, if the self-quantifying vanguard is to be believed. Smartphones are already packed with sensors, from cameras and GPS to accelerometers and gyroscopes. A growing range of cheap consumer gadgets aimed specifically at self-trackers is being launched, such as the Zeo, which monitors sleep cycles, and the fitbit, which measures physical activity and estimates calorie burn.

At the Amsterdam gathering, Robin Barooah, 39, an English software and product designer who lives in Oakland, California, spoke about his experiment in which he claims to have lost 20kg of his original 100kg weight by writing either the word "lethargic" or "energised" on a flash card at 3pm every day for 18 months, depending on how he felt. He puts it down to improved self-awareness.

"I gradually noticed that my perception of some foods shifted from thinking they were delicious to starting to feel their heaviness and the effects they were going to have on me. The act of paying greater attention has an effect on your behaviour."

Christian Kleineidam from Berlin was left with reduced lung function following treatment for a serious spinal condition in 2002. Traditional treatments such as physiotherapy and an inhaler didn't help, so he began taking measurements with a device called a peak flow and forced expiratory volume monitor. This revealed that his lung function improved when he performed certain relaxation exercises. By focusing on these he says he improved his lung function by around 30%.

Dozens of personal experiments such as these were reported and discussed in Amsterdam. Their flaws, such as the likelihood of other, confounding factors being involved, are obvious. But proponents of a more individualised approach to health argue that traditional clinical trials also have flaws, such as producing results that are averaged over groups that may not apply to individuals with particular genetic make-ups or other variations. Some even talk of "hacking" their own bodies – using the more detailed information to change things for the better.

"We all look for information about how to improve things for ourselves," says Barooah. "You can look to other people to provide advice, by going to the doctor or reading a book. However, by definition conventional, mass-produced knowledge is broad and non-specific. By collecting your own personal information you know it is appropriate to you as an individual."

Steve Dean of product innovation studio Prehype and organiser of the New York Quantified Self group, told conference participants about Asthmapolis, a system on which he worked as a designer. Asthmapolis links sensors attached to the inhalers used by asthma patients when they have attacks to smartphones, which gather data on where and when they are used. Tracking this information over time helps patients identify the triggers that make their conditions worse. Patient tests are due to start next year.

But it is the combination of data from large numbers of individuals that may be most likely to lead to new insights. Thousands of patients are carrying out their own crowdsourced comparisons of symptoms and treatments for more than 500 illnesses on the social networking health website CureTogether. For example, one of hundreds of data aggregations revealed that people who experienced vertigo in conjunction with migraines were four times as likely to have painful negative reactions when using the migraine drug Imitrex as those who did not have vertigo.

Sponsors of the conference included big names such as Philips, Vodaphone and Intel. Their funding provided for unusual refreshments including "weed grass" cocktails, which may or may not have been wheatgrass, and a table of fruit including exotic star and dragon fruit, and rambutan. The organisation and language was very Californian, with frequent breaks to facilitate "spaces for conversations" about our "journeys" as well as numerous spontaneous agenda changes.

Gary Wolf, a journalist and co-founder of the Quantified Self movement, argues that the combination of the proliferation of small, cheap sensors, portable computing and the emergence of social media is bringing about profound shifts that are laying the groundwork for self-quantification to enter the mainstream. He says the same early adopters who turned computers from scientific data-gathering machines into the core tools of our personal lives are the same species as the self-quantifying pioneers who are pushing personal data tracking as a logical and inevitable next step in human development.

"Some decades ago computing was for doing calculations so that managers and scientists could better understand and run the world, but then it began to mean communication, self-expression, education, the development of personal knowledge," he says.

"We advanced users are not like other people. We are strange. Look at all the weird stuff we're willing to do. But advanced users teach new technologies to do new things. They are willing to use tools that are harder, but they use them for many of the same human purposes that everyone wants to use them for. We use them to sleep better, understand things about diet, our work and productivity, our learning, our moods.

"If we use our imaginations we can easily see how the homemade or complicated tools we use for self-tracking might have popular incarnations very soon."