Do you track your steps, sleep and food? You could be signing away your privacy

Big tech encourages health monitoring from heart rate to glucose level, but is it too much?

First we counted our steps, then our heartbeats, blood pressure and respiratory rates. We monitored our sleep, workouts, periods and fertility windows. But there is plenty left to measure as we are sold the promise of self-optimisation by the vast and sometimes controversial frontier of health tracking – an increasingly medicalised market that has flourished since pedometers went digital and watches got smart.

The latest health metric available to consumers comes from a medical device originally designed for people with diabetes; it allows users to track their blood sugar levels. But, as always, the big questions are: will it make us healthier, and is it wise to sacrifice ever more intimate data?

There is no doubt that the device, the FreeStyle Libre, which the HSE has been reimbursing some patients for since 2018, is a revolutionaryway to monitor blood-glucose levels for people with diabetes. Rather than prick a finger and squeeze a drop of blood on to a testing strip, a patient could stick a coin-sized sensor with a tiny probe to their upper arm. The painless probe barely pierces the arm, measuring glucose constantly via liquids just under the skin and giving a readout with the swipe of an electronic reader.

If I saw a spike I'd know what had caused it and avoid that food, because I had the memory of the spike, rather than weighing myself every day and thinking, It's going okay overall

The system promised way more data and control for people with diabetes, who try to avoid dangerous peaks and troughs in blood-sugar levels. Soon they could pair their phones with the sensor, keeping a record in an app without ever having to draw blood. It was a life-changing marriage of medical and consumer technologies.


Laura Douglas isn't diabetic, but a few years ago she began experimenting with one of the sensors, which is made by the US health corporation Abbott Laboratories. In the simplest terms, spikes in sugar levels can induce hunger. You eat a biscuit and your levels go up, then crash: you want another biscuit.

“I found it almost rewired my brain,” says Douglas, a 29-year-old engineer and health researcher based in London. “If I saw a spike I’d know what had caused it and avoid that food, because I had the memory of the spike, rather than weighing myself every day and thinking, It’s going okay overall.”

In 2018, Douglas founded MyLevels. The startup, which is in the testing phase, pairs FreeStyle Libre sensors with its own app to understand the effects of foods on an individual's glucose response, using artificial intelligence to recommend a personalised diet. "A lot of diets will tell you not to eat when your sugar levels crash," says Douglas, who is from Edinburgh and has a master's degree in machine learning. "We say: 'Don't spike too much in the first place.'"

MyLevels has sent sensors to about 300 trial customers around the UK; it plans to launch fully in a few months. (A 14-day programme costs £139, or about €165.) Customers are invited to eat test foods, such as a bar of Dairy Milk, to get a range of individual baseline responses, and log what they eat. Foods are then scored as part of a new recommended diet that aims to avoid sugar spikes.

Douglas is not alone. "The use of continuous glucose monitors in healthy individuals is an exploding area," says Sarah Berry, a senior lecturer in nutritional sciences at King's College London and an expert in postprandial metabolism, or the way we respond to food.

Berry is an adviser to Zoe, a health-science company founded in 2018 that monitors glucose levels as well as body fat and gut health. Meanwhile, Supersapiens, an American app that is available in Ireland – uses glucose monitors to optimise diets and training for top athletes. There were rumours that Apple was going to add glucose monitoring to its latest smartwatch, which goes on sale later this autumn. It didn't, but new devices that use technology called spectrometry are in the pipeline. These can "scan" for blood-glucose levels in your wrist without a probe.

Scientists are pushing the limits of technology and consumer demand, cramming shrinking circuitry into wearables, including smart patches that will work as one-stop diagnostic and tracking centres. "We've probably reached the point where we're mostly satisfied with the size and functionality of our phones," says Sara Ghoreishizadeh, an electronics engineer at University College London, where she is developing a smart mouthguard. The device will track acid levels and hormones in saliva to determine metrics including dental health and sleep quality. "Now it's time to develop stronger technology to allow us to track our health."

I watched the announcement of the new Apple Watch last month with interest. A few weeks earlier my Garmin smartwatch gave up the ghost. Before that I wore a Fitbit to count steps, track my pulse and sleep, and record runs and bike rides. My instinct was to get a replacement. I decided to wait to see how much the new Apple device would cost. Still keen at least to track the time while I waited, I dug an old Casio out of a desk drawer.

It can all seem benign and nice – but what if that data also gets used to decide who gets the next promotion or whose health-insurance policy needs adjusting?

For several weeks I have worn nothing more on my wrist than the time. And – spoiler alert – it has been fine; a relief, even. I no longer feel the need to track every mile I ride or step I take. My activity levels haven’t changed – and I don’t need a device to tell me I have slept badly. But I have a problem, because my health-tracking data has become about more than my own curiosity and good intentions.

A few years ago, in a fit of grownupness inspired by new fatherhood – and my dad’s early death, 20 years ago – I took out life insurance. Like many policies, it links premiums to lifestyles rather than crude metrics such as age and life expectancy. My Garmin account, to which my watch transmitted my step counts and activities, is linked to my policy.

I win points daily by walking far enough or burning calories during activities, as estimated by the rises in my heart rate measured by a smartwatch. My annual points total affects my insurance status and premiums. The more active I am, the less likely I am to die young – and the less I pay.

Although my lifestyle hasn’t changed since my Garmin died, my insurer thinks I have become idle and therefore at greater risk of life-shortening conditions. It hasn’t contacted me, but if I go on like this, without collecting points, I could face higher premiums.

Such quandaries will only become more common and complex, says Btihaj Ajana, a reader in media and digital culture at King’s College London and a specialist in self-tracking. She traces our tracking instincts in the digital age to the “quantified self” movement. It took shape in 2007 as a way for individuals to use technology to optimise themselves like machines. “What started as a positive phenomenon then got hijacked,” Ajana says.

Constant advances in tracking have given tech companies new ways to keep selling their latest devices, while happily collecting the data we generate and sign away without reading the terms and conditions. “You don’t own that data,” Ajana says. Apple promises to encrypt and guard the multiplying streams of health data it collects for us. But much of the concern about privacy in this growing market is what we consent to share with third-party apps and services that have their own privacy policies. “We are so blase about privacy,” Ajana says.

It is easy to imagine the value of health data not only to insurers but also to advertisers and employers. Around 2014 a number of big businesses started giving Fitbits to staff, collecting information on their sleep, activity and location. The rise of corporate tracking, which is presented as an employee perk – Free watch! Better health! – may be hastened by Covid. LifeSignals, a California startup that has developed a chest patch to measure signals including breathing, temperature and even posture, noted a spike in demand last year from big businesses that wanted to screen staff for Covid symptoms.

“Some employers ask employees to compete with each other to be more healthy,” Ajana adds. “It can all seem benign and nice – but what if that data also gets used to decide who gets the next promotion or whose health-insurance policy needs adjusting?” Opting out of such programmes can feel like a career risk of its own.

Meanwhile, the range of data that is being gathered and assessed grows. NatureQuant, a startup in Oregon, is developing an app to track and rate the time we spend outside – not how many steps but where we step, based on the well-established health benefits of fresh air and green space.

The company gathers data, including satellite imagery, street-view photography, road densities and measures of air pollution, to score any location (so far only in the United States). GPS location tracking then pairs user and place. Going for a walk, for example, would earn you a “nature dose” in minutes, towards a 120-minute weekly goal, and a “nature score” based on how green and pleasant it was.

NatureQuant is open about wider interest in its data. "We're in conversations with big insurance providers to provide NatureDose as a tool to improve population health," says Jared Hanley, the company's chief executive. Employers are also keen, as are property developers, who might use nature scores to identify and promote new sites.

Privacy policies vary between health apps, many of which tap into the sensors and hardware developed by device manufacturers. Earlier this year the New York Times analysed the policies of 250 iPhone apps, including 20 health and fitness apps. Thirteen of these apps shared data with an average of three third-party trackers, many of which passed data to advertisers.

The apps included Flo, a period and fertility tracking app used by more than 100 million women. In January, Flo agreed to a settlement with the US Federal Trade Commission after it had been exposed for sharing health data – including users' period timings and declared intention to conceive within the app – with advertising tech companies, including Facebook.

Flo had not given users an opt-out for such sharing, something it has now agreed to do as part of the settlement. Flo did not admit to any wrongdoing, and denied sharing users’ names, addresses or birthdays, saying in a statement: “We are committed to ensuring that the privacy of our users’ personal health data is absolutely paramount.”

If you became obsessed with glucose response, you could reduce your glycemic variability [blood-sugar spikes] while eating bacon and eggs every day, and your fat response would be all over the place

Douglas says MyLevels does not sell or share any personal data, relying instead on subscriptions. Yet she has been courted by investors “pushing for different business models ... You can imagine advertising targeting you when your glucose levels are crashing,” she says.

For advocates of health tracking, the risk of sacrificing data is worth taking. "There is no digital health revolution without breaching some of our privacy," says Bertalan Mesko, a "geek physician" who, as the director of the Medical Futurist Institute, studies the way technology can change healthcare.

Mesko envisages a not-too-distant era in which “digital tattoos” send health-data streams to our smartphones. An app would alert us to worrying symptoms and arrange appointments with digital doctors, which would prescribe personalised medicines based on our data and genomic sequences. Medicines will be 3D-printed in precise formulations. “And you’ve probably just saved yourself from hospitalisation or even a major medical incident,” he says.

Mesko struggles to understand heightened fears of health data sharing. “We use tech every day that has for years been a threat to our privacy, yet here is tech that could promise a better life and now you have concerns?”

Even if tracking might eventually help spot symptoms early, the extent to which it nudges us into better behaviour is moot. While some studies have shown step-counting, for example, can boost motivation and activity, others have questioned its overall effect on the population, particularly after the novelty wears off.

There is also concern about the precision and side effects of health tracking. In 2018 Apple added an electrocardiogram, or ECG, sensor to its Watch. Until then such monitors were used in hospitals to detect abnormal heart rhythms. Now anyone can be alerted to potential problems, but the US Preventive Services Task Force, an independent panel of experts in disease prevention, has recommended against ECG use in healthy people.

Doctors have expressed concerns, for example, about the accuracy of such tracking, and risks associated with further screening prompted by an alert – as well as the potential for health tracking to induce anxiety or obsessive behaviour. "GPs are under immense workload pressure, and it's important they aren't overloaded with patients submitting readings from smartwatches and fitness trackers if they have not been asked to do so," says Dr Michael Mulholland, the vice-chair of the UK's Royal College of General Practitioners.

Berry, the nutritionist, says glucose responses to food can guide someone towards healthier eating as part of a bigger picture. “But the worrying thing is, if you became obsessed with it, you could reduce your glycemic variability [blood-sugar spikes] while eating bacon and eggs every day, and your fat response would be all over the place.”

Douglas, who says glucose tracking has helped her stabilise her own weight, is aware of the risks of potentially obsessive behaviour in vulnerable customers. MyLevels does not recommend weight loss as a goal to customers whose body-mass index is below 18.5, which is categorised as underweight, she says, but adds: “I honestly think it will do more good for people, as it has for myself.”

I, meanwhile, will continue to wait for the new Apple Watch, with all its promise as a virtual nurse, and then decide if I really need it. How will I balance the convenience and potential benefits to my health and insurance premiums of a smartwatch against the instincts of a burgeoning industry of data gluttons in big tech and advertising? Do I really need digital confirmation of a bad night’s sleep or a lazy day? While I ponder these questions, the only thing I can share is the time. – Guardian