This week, I discovered how many calories I burn climbing stairs, riding trains, sleeping, and having sex. The data come courtesy of a plastic device called the bodybugg, which is currently strapped to the underside of my right arm, like an oversized ladybug about to nuzzle the armpit. The bodybugg is designed to measure the number of calories burned minute by minute over the course of a day, in order to help people lose weight (or gain—it's apparently popular with bodybuilders).
Bodybugg is part of a new wave of personal monitoring gadgets that promise to track various aspects of our health, fitness, or risk of disease. Nike + iPod, for instance, uses sensors in sneakers to track a runner's time, distance, and calories burned. An experimental alarm clock works with a headband that monitors sleep stages, promising to wake you up in a lighter phase so you feel less groggy. A specialty shirt, currently in clinical trials in Europe, is packed with sensors that monitor heart rate and breathing. A toilet now on the market in Japan tests urine streams for glucose, gathering data that could be used to monitor diabetes. These gadgets threaten to serve up more data than we know what to do with, not to mention make us ever more self-absorbed. But they also dangle the hope of better understanding and better health. What's it like to spy on one's own body 24/7? I decided to find out. I chose the bodybugg because it's commercially available, doesn't require the continuous wearing of sneakers, and does not involve renovating my bathroom.
When the bodybugg arrived, a guy named Rich set up my online account and walked me through questionnaires that swerved from the personal to the medical—does "steak for breakfast sound good to me"? Am I "tired in the morning even after 7-8 hours of sleep"? Do I have high blood pressure or food allergies or pancreatitis? Rich explained that he would keep an eye on my data, describing himself as a cross between "a trainer and a stalker." The bodybugg has four different kinds of sensors, he said, to track arm motion, heat flux, temperature, and galvanic skin response. When data are uploaded from the device to the company site, an algorithm crunches input from all four sensors and generates a graph of calories burned.
My bugg didn't look particularly sleek. When I hung up with Rich and strapped it on, it made a feverish whirring sound, vibrated for a moment, and fell silent.
10:40 p.m.: With no particular plans, I fidgeted, clicked on e-mail, opened and closed the fridge.
10:47 p.m.: I decided to see what that living room loop amounted to. I logged in to the site, connected a cable from computer to bugg, clicked a couple more times, and presto—1,632 calories burned!
Not really. Since I'd missed most of the day, the program extrapolated, assuming I'd been fidgeting, checking e-mail and opening and closing the fridge continuously since early morning. Still, running my cursor over the past seven minutes, I saw I'd averaged a little more than a calorie per minute: 1.6 calories a minute walking around and 1.3 calories a minute deleting junk mail.
In the morning, I discovered that sleep burned off another 600 calories. I could pinpoint a spike just before midnight when I'd brushed my teeth (2 calories a minute). Then the graph dipped where I got into bed, and I could see the moment I nodded off: a further dip to 0.9 calories a minute. For the rest of the night, I oscillated between 0.8 calories a minute and 1.1 calories a minute, maybe cycling through various sleep stages or dreams.
The company's Web site has an option to log food intake, which allows dieters to compare input with output. But after fussing with the drop-down menus—scrolling through protein-fortified yogurts, presumably for the body builders, and finding nothing much like the sandwich I planned to eat for lunch—I decided to estimate calories on my own.
In any case, it was time to put the bugg through some paces. At the gym, I looked skeptically at the Nautilus machine readout, which told me I was burning between nine and 10 calories a minute. That estimate was based broadly on my age, weight, and rate of strides at a given resistance level. It seemed a little high. My friend Matthea insisted we do extra push-ups, to see if they were really worth it for the future.
Outside, it was pouring. I had to get to Columbia Medical School for a lecture, which meant switching trains several times—now at least I figured I'd have proof of how taxing city schleps can be. Sitting on the train, running through the rain, meeting up with friends, dropping in to an art opening … It wasn't bad to feel that every moment was somehow tallied. It's nice to get credit just for existing
At home again, I slipped the bugg off my arm and plugged it in for the day's results. I discovered that gym machines indeed should not be trusted. I'd burned no more than 5 calories a minute working out, plus 3.7 calories a minute for the push-ups, 3.6 calories a minute running up subway stairs, 1.7 calories a minute pacing the platform, and 1.4 calores a minute sitting on the train, whether reading sci-fi or staring up at personal-injury lawyer ads. (So much for more calories for the tedium or stress of the trip.) My friend's art opening consumed 1.7 calories a minute, more than walking around at home, maybe because the room was hot and crowded, and I was navigating while tipsy on two pink drinks. The data were almost a microdiary of the day. I was already hooked on my own read-out and hungry for an even finer-grained portrait—what about the little energy spikes of chewing, sneezing, opening and closing my umbrella, blinking, yawning, or laughing?
I also began to wonder how I compared with other female thirtysomethings. In the course of the week, I burned between 1,500 and 2,000 calories a day and ate roughly the same amount. Work consumed only slightly more calories per minute than sleeping. And having sex burned fewer calories than aerobic exercise at the gym (though research on this is ever ongoing).
Self-monitoring may have upped my motivation, but I'd probably really have been driven to new heights if I'd been posting my data. I haven't quite seen the appeal of microblogging sites like Twitter, which allow users to blast zillions of short posts on what they're doing, where they are, what's on their mind. But obsessive sharing seems useful when it comes to fitness. The bugg does not have a social networking component; Nike + iPod, on the other hand, has a platform that allows runners to compare notes and challenge one another through the data they share online. Researchers predict that groups of friends or patients will someday keep tabs not only on one another's exercise routines or weight loss but on vital signs or heart patterns or blood glucose levels. (Think Facebook meets the diabetes toilet.)
In theory, all this could produce more than just a heap of physiological trivia; it could be a treasure trove for medical research. If companies can churn out gizmos that are cool and fun—and just useful enough—people may be willing to pay to gather data on themselves. And if the information is uploaded or shared, scientists might someday have access to copious minute-to-minute records, unlike anything available today. Then they might be able spot patterns to help predict when people are likely to have heart attacks or suffer memory loss or pull a muscle or slip into depression. I know the bodybugg sounds sort of indulgent, but it all could be game-changing for medicine.
Of course, only a fraction of today's ideas will turn out to work or have real utility. And just as certainly, privacy concerns abound. Last year, computer scientists discovered that Nike + iPod users could be easily tracked by strangers, since the sneaker-to-iPod signal was easy to intercept. (Nike did not return calls asking whether the problem has been fixed.) When it comes to physiological data, I'd rather see better protections built in from the beginning, with names and identifying features omitted.
Still, my week with the bugg nudged me closer to seeing the appeal of a true mechanical diary—an ongoing objective record of my body's interior. And I'm planning to keep the little guy on my arm a little longer, if only to see how many calories it takes to finish this article.