I’ve always loved training related gadgets and hope to look at some of those over the coming months in future articles. While most of what I’ve been interested in related to training (e.g. heart rate monitors or what have you) some gadgets help with fat loss and body recomposition. Digital scales and such are part and parcel of many people’s diets of course but here I’m talking about slightly higher tech-stuff.And today I want to look at something that, while not exactly ‘new’ (it’s been around for a few years at least) certainly has a lot of interest and questions about it. And that is the Bodybugg/GoWearFit. Now strictly speaking, both of these devices are different, but they are both made by the same company. And are essentially the same device. So far as I can tell the biggest difference is that the GoWearFit (hereafter GWF) uses slightly different software than the Bodybugg but, for all practical purposes, I’m going to consider them the same device. This is what it looks like.
Go Wear Fit
The device is worn on the left arm, around the middle of the triceps with the bit shown above facing backwards. If you can’t picture that, I’m sure you can Google an image up.
What is it/How Does it Work?
The GWF is actually one of several different recent devices the purports to measure caloric expenditure. While things like heart rate monitors have claimed to this for a while based on heart rate, the GWF type devices got a bit further including 5 different sensors which measure acceleration, temperature, steps, galvanic skin response and heat flux. It plugs all of those into an algorithm and calculates how many calories you’re burning on a minute to minute basis. Some of that algorithm is based on your height, weight, age, gender, etc. that you plug into the system after you sign up.
The device is then plugged into a computer and the data uploaded to a piece of software that interprets it and shows your caloric expenditure over the course of hours or days or whatever. I’d note that there is also an additional watch that can be purchased that will show you a more or less real-time (it’s actually averaging every 6 minutes) measure of caloric expenditure. This can be useful if you’re tracking workouts to a ‘Burn XXX total calories’ goal. But for measuring daily expenditure, you’ll generally use the online tracking software (which also stores previous days which can be nice).
From a technical standpoint, the GWF uses a standard USB cable and charges off of the computer itself (I think this was one big difference than the Bodybugg which used AA Batteries). It lets you know what the battery status is and holds a charge pretty well. If you get in the habit of hooking it up while you’re in the shower, it will stay charged for quite some time.
I’d mention that the device is pretty sturdy and you can sleep with it. One of it’s more interesting features, which I’ll mention below is that it gives you an estimate of sleep efficiency, effectively the percentage of time that you’re actually asleep while you’re laying down. I have no clue how it does this but it seems to be accurate (e.g. it’ll catch if you wake up and roll around or get up to pee or whatever); I honestly suspect a pact with Satan is somehow involved.
The online software is actually fairly good, even if their server seems to have issues with access more often than it should. It will access the armband via a standard USB port and give you a lot of different data including caloric expenditure, sleep efficiency and others. It also has some basic calculators for things like energy expenditure for different activities (e.g. enter that you ran 60 minutes at 6.5 mph and it will spit out calories. You can also get weekly average reports and such.
One thing I want to mention that the GWF does NOT do but some people think it does. On the site, they mention that they will let you track caloric intake. And you can but you do it manually, by entering food records. The device in no way actually measures what you ate in a day. And while a new device worn on the arm claims to do just that, apparently it’s only accurate to plus or minus 500 calories per day which is useless as hell. But the GWF does not measure caloric intake, you can enter your food online manually and that’s it.
I would mention that their interface only works with selected Browsers and this can get irritating; the last time I looked for example, Safari 4 was not supported and neither was the higher build of Firefox for Mac. When I updated my browser I lost the ability to access the online software.
Is It Accurate?
A limited amount of validation data has been done on the GWF but has found that it is at least reasonably accurate. Certainly nothing is 100% and the GWF isn’t either. It seems to mis-estimate certain situations more than others but, overall, seems about 90% consistent or so with other, more accurate measurements. Which is pretty good for the most part.
Speaking empirically, I’d note that I’ve played with the GWF in myself and one of my trainees and compared the values it spits out to other measures. For example there are standard calculations for resting energy expenditure based on body surface area, the GWF hits them pretty much exactly.
I’ve also compared it to things like a heart rate monitor measurement of exercise energy expenditure, as well as the number that the machines spit out themselves. The numbers are never exactly the same but they are always within shooting distance of one another. Certainly the difference is never massive (and since these are all estimations, this is no surprise).
Since I’ve mentioned my Powermeter bike on the site before, you may be wondering if I’ve compared GWF values to the kilojoule numbers the bike produces. And the answer is no. One place where the GWF completely craps out is in estimating cycling energy expenditure. Since one of it’s major determinants is the accelerometer, and that only works if the left arm is moving, the GWF does a horrible job with things like cycling (their site even acknowledges this). I’ve seen it suggested to wear it on the calf while cycling but never tested this out to see if it gave better numbers.
I’d note in that respect that it is possible, in activities where the left arm is being moved vigorously for the GWF to produce absolutely insanely high caloric expenditure values. Just impossible values. I’ll let the more dirty-minded readers do with that statement what they will. Moving on.
I’d note that the daily caloric expenditures that the GWF spits out come awfully close to some of the standard estimations that I’ve thrown out on the site. Which actually raises the question of what the GWF does that the method described in How to Estimate Mainteanance Calories – Q&A doesn’t do for free. Which is a good question.
I’d also note, and this based purely on forum feedback, that the GWF seems to just be horrible at putting out good values for a small percentage of people. I’m not sure why this is the case but a generality that seems to be showing up is that folks with thyroid issues don’t get a good measurement off the GWF, it seems to overestimate.
I’d note that this conclusion is being based on people looking at weight changes relative to what the GWF is saying their expenditure is and what the ysay their caloric intake is. This introduces a number of possible problems (not the least of which being thyroid mediated water retention that masks fat loss or problems with actual caloric expenditure).
But for the most part, I’ve found that the GWF not only correlates well with both standard equations and other measurements of energy expenditure, it can pick up changes in activity very reliably. Get up and walk around for a few minutes, and the GWF will pick it up; go watch a movie and you’ll get a value that is not dissimilar from sleeping for the entire time. It’s not perfect but it’s damn good.
Why Should You Care?
Even with standard estimate equations like the ones I constantly talk about on the site, there can still be some real questions about total daily energy expenditure. If nothing else, the GWF at least takes a decent stab at actually measuring it. For people with either very high or very low activity (or simply activity that changes a lot on a day-to-day basis), having an actual number to put with that activity can be helpful.
So, in terms of who the GWF can be good for, one of those is the typical dieting obsessive compulsive. For those people who just have to have a better value than what estimate equations provide, the GWF is worth considering.
As well, for people who have varying activity levels, whether in terms of work or exercise training, the GWF can help to get values on the different workouts. Days off or very easy days may end up having very different energy expenditures than heavy training days. Athletes or dieters trying to really match intake to output can get data on those different days to better set their nutrition.
The GWF can also have a couple of other less obvious uses. One of them is this: many people find themselves subconsciously trying to move more when they start using the GWF. The graphs are kind of exciting and people start moving more to watch the numbers go up (one trainee who used it had a goal of hitting a 4000 cal expenditure day for example). It’s like when you make people start writing down their food and they start eating less spontaneously. Something about knowing that the device is measuring energy expenditure makes people want to move more.
In that vein, one of the more intriguing things that the GWF shows is how much small bits of activity throughout the day really add up. That is, the difference between someone who literally sits for 8 hours per day and one who gets up even a few times during the hour to move around can add up to a fair few hundred calories. Over the course of a week or a month or a year this makes a massive contribution to energy output.
Related to that, many people are actually quite disappointed to learn that activities of daily movement often burn far more calories than formal exercise. One trainee was distraught when she found that 3 hours of yardwork burned TONS more calories than 3 hours in the weight room.
A final effect (more than a use) of the GWF is that it’s done a good job of getting people who ‘swear they only burn 1200 calories a day and have to starve to maintain weight’ to realize that their daily energy expenditure is actually much higher than that. Many people on forums have found that they can raise calories a lot higher than they had been eating without weight or fat gain. Basically, it ends the “Slow metabolic rate/low energy expenditure” claim because it gives objective data on what’s really going on. Of course, people determined to believe that they are special will just ignore the data.
But in terms of actually getting a good estimate on what different days of the week or different activities burn on a day to day basis or what have you, the GWF is a step above using an estimation equation or trusting the caloric expenditure reading on the treadmill.
I should mention sleep efficiency. As I discussed in Obesity and Inactivity: The Relevance of Reconsidering the Notion of Sedentariness sleep deficiency is not only fairly widespread in modern life but a real problem in terms of health and propensity to weight gain. One thing the GWF does is give a measure of sleep efficiency, a simple percentage indicating how much of the time laying down was spent sleeping.
This gives users the ability to track how lifestyle changes (e.g. sleep hygeine, sleep supplements) are impacting their sleep so they can try to raise the total amount of sleep they are getting. You can test different dinner meals or when you train or whatever and see what gets you higher efficiency numbers (my limited googling suggests that 85%+ is a good value, nobody gets 100%). For people with sleep issues, the GWF might be useful just for that.
What’s the Catch?
So the above section is sort of the pros of the GWF. Let’s you get a more accurate picture of what you’re doing on a day to day or workout to workout basis, etc. What are the cons?
The first of course is price. The unit is not cheap (it’s not absurdly expensive), Amazon currently lists it at $179.00. However, for reasons I’ll come to, you can usually pick up one on Ebay. Unfortunately, that’s not the only cost involved. To get the data off the thing you have to have a monthly account with Bodymedia to access the data. And no you can’t use the watch to get around this, it will eventually fill up and you can only clear it out by accessing the website.
Admittedly the website isn’t expensive, like $12.95 per month or something (I can’t actually find the value on their site at the moment). I’d note, and they go out of their way to avoid admitting this is the case, but you can transfer accounts. So if you chose to buy a unit off of Ebay you can take over their account and change the user data and it will work just fine.
Also, the GWF can’t be purchased outside of the United States; I have no idea why but anybody who isn’t in the US will have to have a friend buy it and ship it over.
And that brings me to possibly the biggest issue with the GWF. For most people, day to day and week to week activity doesn’t change massively. You probably work Monday through Friday, weekends off, train certain days and you’re training is unlikely to change massively over time (this may be different for athletes whose training changes a lot during the year).
What this means is that after you’ve gathered data with the GWF for maybe 2 weeks, it becomes fairly useless. Unless you’re in that situation where your activity is highly variable, you’ll have every thing you need from the device after that short time span. And that’s a fairly large investment for 2 weeks of use.
There are options around that. One is to buy one used off of Ebay. And then sell it again when you’re done with it. As I mentioned, you can change the user data and transfer accounts even if GWF says you can’t. Another option is to get together with a few like-minded fitness obsessives and buy it in a group. Split across 4-6 people, it’s fairly cheap and you can just rotate it through every 2 weeks as people use it and get the data that they need.
So the GWF, is it worth getting? Overall I say yes. It’s one of the more accurate devices and for people trying to optimize their overall nutrition and body recomposition can provide some rather invaluable data on what’s actually going on. The problem being that, once you have those 2 weeks of data, it’s fairly useless. You can keep using it, and if your training changes or increases drastically, it may have use beyond that. It’s not super-cheap and the monthly fee to use the website is annoying but that can be gotten around with creative sharing or Ebaying.
About the Author Lyle McDonald
Lyle McDonald is the author of the Ketogenic Diet as well as the Rapid Fat Loss Handbook and the Guide to Flexible Dieting. He has been interested in all aspects of human performance physiology since becoming involved in competitive sports as a teenager. Pursuing a degree in Physiological Sciences from UCLA, he has devoted nearly 20 years of his life to studying human physiology and the science, art and practice of human performance, muscle gain, fat loss and body recomposition. Lyle has been involved, at various levels of success in competitive sports since his teens. Starting with triathlon, he spent altogether too many hours on his bike during college. Becoming involved with inline skating at the same time led him to compete for several years until he burned himself out with chronic overtraining. Many years passed until he decided to return to speed skating and move to the ice. He moved to Salt Lake City Utah to train full time at the Olympic oval, he is currently still there training with his coach Rex Albertson attempting to make the US National team or beyond.Lyle has written for the print magazines (Flex and the now defunct Peak Training Journal), too many online sites to mention (including Cyberpump, Mesomorphosis, MindandMuscle, ReadtheCore) and has published 5 books on various aspects of exercise and diet. Over the years, in addition to working with the general public, Lyle has worked primarily with endurance athletes, a few powerlifters, and some bodybuilders. Through his books, articles and his forum, he has helped thousands lose fat, gain muscle and get stronger or perform better.