Measuring Calorie Expenditure with a BodyMedia

 know I’ve been M.I.A. for a long time, but I’m back because I have something really interesting to talk about: my BodyMedia!

What’s a BodyMedia?

A BodyMedia is a on-body device that tracks your footsteps, heartrate, sleeping patterns, and daily calorie expenditure, and then uploads them to an online dashboard for you to easily view and track.

It looks like a wristwatch worn on your upper left arm, but in fact it’s a sophisticated device that constantly captures data on your movement, skin temperature, and energy expenditure, then uses this information to determine your caloric burn. It’s more sophisticated than a pedometer or heart rate monitor because neither of those can accurately measure calorie expenditure–this does. Of all the products out there, this is the most accurate, with no guesswork or estimation on your part. You can learn more at the BodyMedia website.

Why Use A BodyMedia?

The BodyMedia produces so much data that I haven’t had time to explore all of it’s potential uses, but for now I’m going to focus on calorie tracking. If you’ve ever tried to lose weight, chances are at some point you’ve thought about calories. Too many people obsess over counting and measuring and tracking every bite of food in order to hit some magic calorie goal without ever stopping to consider whether this is the right amount for their body and weight loss goals. Or they spend hours surfing the web and reading articles and crunching numbers trying to figure out how many calories they just burned at the gym and how many miles they need to run to “burn off” last night’s dinner. Or they get hung up on hitting the right number of “net calories” *cough everyone on tumblr cough*, a concept that is inherently meaningless.

None of this makes sense, and none of this is the right way to think about food, exercise, and weight loss. It doesn’t make sense to pull a calorie goal out of thin air without first considering your calorie expenditure. It doesn’t make sense to meticulously track your exercise calories when they’re really just a rough estimate. And it doesn’t make sense to fixate on the calories you burn in an hour at the gym without thinking about the calories you burn during the other 23.

Calories aren’t just something that you burn off running on the treadmill; they’re units of energy that your body uses constantly to survive. Your body doesn’t just shut off when you’re not formally exercising; it’s burning calories constantly as your working, studying, eating, sleeping, and otherwise going through the motions of daily life. This is why trying to eat back your “exercise calories” to hit 1200 “net calories” is so silly: your body doesn’t differentiate between “exercise calories” and any other calories–all that matters is that your intake is less than your output.

Problem is, how do you know your calorie output? A magazine article can’t tell you. An online calculator can’t tell you. And the computer screen on the elliptical sure as heck can’t tell you. These estimates are a good place to start, and they’re certainly better than pulling a number out of thin air. But if you’re going to let your life revolve around those numbers, then you should at least make sure they’re the right numbers, right?

And that’s where the BodyMedia comes in. It eliminates the calculations and estimations and guesswork by giving you an accurate picture of your daily calorie expenditure. It tells you more about your own body than a doctor, trainer, or one-size-fits-all formula ever could. If your goal is to lose weight, it will enable you to calculate exactly how much you need to eat to reach your weight loss goals, allowing you to avoid sabotaging yourself by eating too much or too little. Moreover, you will be able to see the impact that different exercises, activities, and eating styles have on your body both at the time and throughout the day, helping you to find the lifestyle that is best for YOU.

Why I’m Using A BodyMedia

I get asked this all the time at work when my coworkers or tables see my BodyMedia! Right now I’m just using it to gather data and learn more about my body. I’m not actively trying to lose weight in the sense that I’m tracking or limiting my calorie intake–I’m just curious about my calorie expenditure. Specifically I’m interested in how weight-lifting impacts calorie expenditure in the short-term (how much does it increase calorie burn on a daily basis) as well as the long-term (can it permanently increase your metabolism?) I’m also curious about how much I’m burning at work waiting tables.

My BodyMedia Data

First here’s some background on me: I’m 22 years old, 5’8, and about 150 lbs. For the past month, I’ve been lifting heavy weights for 30-75 minutes 4-5x/week. I also have a very active job waiting tables 30-40 hours/week, and am usually fairly active when I’m not at work (biking, housework, running errands etc). Based on BMR calculations, my BMR should be around 1520 calories, meaning that my calorie expenditure should be about 2600 – 2900 assuming a high activity level. I’d estimate I eat about 3000 calories per day, but that’s just a guess since I don’t currently track calories.

I’ve been wearing the BodyMedia since November 9. Shown below are 17 days worth of data (rounded to nearest 10):

During this 17 period, I burned an average of 3290 calories per day. My calorie expenditure ranged from 2430 to 3860 calories. I expended over 3000 calories on 13 out of the 17 days.

My first reaction was, holy shit, no wonder I’m always hungry! This explains why I eat so much! My second reaction was to wonder about the variance from day to day–that’s almost a 1500 difference between the highest and lowest days!

However, this disparity makes sense if you take into account my activity level, particularly the two biggest factors: lifting weights and working. I’ve reproduced the data below using an “L” to indicate days that I lifted, and “W” to indicate days that I worked.

During this 17 day period, I worked 14 days and lifted 10 days. There were 8 days when I lifted and worked, 6 when I worked but didn’t lift, 2 when I lifted but didn’t work, and 1 when I did neither. I summarized the averages for each category below:

  • Worked and lifted (8 days): 3540
  • Worked but didn’t lift (6 days): 3100
  • Lifted but didn’t work (2 days): 3260
  • Didn’t lift or work (1 day): 2430
  • Overall worked vs didn’t work (14 days/3 days): 3350 vs 2980
  • Overall lifted vs didn’t lift (10 days/7 days): 3490 vs 3000


Right now my conclusions are preliminary because I don’t have much data–I just wanted to share what I had now! However, here’s a few of my thoughts right off the bat:

  1. First off all, I’m burning a LOT of calories. Significantly more than you’d expect based on standardized calculations for my age, size, and activity level. It’s a good reminder that estimations are just that–estimations–and the standard 2000 calories/day doesn’t apply to everyone–if you’re young and active you probably can and should be eating more than that.
  2. Lifting makes a difference. I average almost 500 calories more on days that I lift versus days that I don’t (3490 vs 3000). HOWEVER, this doesn’t mean that I necessarily burned 500 calories during that particular hour of lifting–just that lifting increases overall daily burn (the BodyMedia can show the exact calorie burn during a particular time to prove my point, I just haven’t analyzed it that deeply yet).
  3. Also just because I average 3000 calories per day on my days off from lifting doesn’t mean I’d burn 3000 calories anyway if I’d never picked up a weight. Your metabolism depends on your general pattern of activity, not just your day-to-day activity, and I have a feeling that if I took a month off lifting, my baseline would be much lower. I’m not going to do this on purpose, but it might occur naturally, hence my effort to constantly gather data for comparison purposes.
  4. Activity level matters too: an active lifestyle beats hours of cardio. Over these 17 days I averaged 370 calories more on days that I worked (3350 vs 2980). Moreover, when I look at the breakdown of individual days, I can see a big difference–all the days I hit over 3600 calories were ones I worked long, busy shifts and/or was active outside of work (in addition to lifting). Note that none of this is “formal exercise” but it still burns calories.
  5. My metabolism didn’t used to be this fast. In fact, my whole life I thought I had a pretty slow metabolism, based on the fact that I was overweight as a kid despite having normal eating habits. But I believe that you can increase your metabolism by weight lifting and by EATING, and this supports my belief.
  6. On the other hand, I don’t think I’m eating and expending exponentially more calories than the average person–I just think I’m more aware of it. Most people can and do eat more than they realize, but they aren’t really tracking their intake so they just assume they’re eating the “normal” amount you commonly hear thrown about: 1500, 1800, 2000 etc. When people do track calories it’s usually because they’re trying to lose weight, so that number isn’t going to be representative of an average day. And everyone underestimates.
  7. Based on this you can see why low-calorie diets are often doomed to fail. If Joe Schmo thinks he’s eating about 2000 calories a day, since that’s what the cereal box says (seriously, I’m pretty sure this is where I got my idea of a”normal” amount of calories from), then a 1500-calorie weightloss plan sounds reasonable. But in reality, he’s eating more like 3500 calories a day, he just doesn’t know it. So when he goes on a 1500 calorie doctor-approved diet plan, he feels like he’s starving–because he literally is. After a few days he can’t take it anymore and goes on a fast food binge. Or decides dieting is impossible and gives up altogether. Whereas if he had changed his target to 2500 calories he could having stuck to the diet for much longer, steadily losing 2 lbs/week until he hits his goal.

Stay Tuned…

I need to wrap it up for now, but I’ll be back with more posts as I get more data and delve more deeply into the data I have. I hope this was helpful and feel free to get in touch with any questions; I intend to be more active on here from here on out!


Why I Don’t Eat Back Exercise Calories (And Why You Shouldn’t Either!)

One of the questions I see all the time in the online health/fitness/weight-loss community is whether or not you should eat back your exercise calories. The general consensus seems to be yes. I say no. I don’t eat back my exercise calories, or even track them at all! Here’s why:

The simple reason is that to calculate my calorie needs, I take my BMR (Basal Metabolic Rate–the number of calories your body would burn everyday if you were lying in a coma), and multiply by an activity level factor, then subtract to create a deficit if I want to lose weight. (I explain how to do this here). I eat that number of calories on a daily basis, whether I exercise that day or not. My general level of exercise is already reflected in my choice of an activity level multiplier, so if I ate back my exercise calories I would be eating them twice!

Of course, the other alternative would be to use your daily calorie needs at sedentary (or some other arbitrary calorie level) as a baseline and add back exercise calories on a daily basis. This seems to be the more commonly accepted approach. However, I find this approach problematic for multiple reasons. Here’s why:

1. Eating back calories is inconvenient for planning ahead and meal timing

So you might go to the gym at night after class, in which case you’ll probably burn 500 calories. Do you eat those calories now or later? If you wait until afterwards, you won’t have enough energy for the gym, so you should probably eat them now, maybe in the form of a delicious grilled salmon salad while you’re out to dinner with your friends. But what if you don’t make it to the gym–you’ll go over your calorie count for the day! So instead you order a dry side salad, and plan to gulp down an unsatisfactory protein bar on the way to the gym if you end up going. Wouldn’t it be so much easier just to know in advance how much you can eat every day?

2. In fact, your calorie needs shouldn’t actually change that much from day to day

The majority of the calories you burn come from just living–breathing, circulating blood, digesting food, as well as the activities you do on a day to day basis. You need these calories every day whether you exercise or not. And if you do exercise on a regular basis, your needs should be fairly consistent too. For example, if you’re training for a marathon, you’ll want to fuel on the days before your runs, not just on the days you run. If you lift weights, the muscle growth and repair process actually happens in the 48 hours afterwards, so your body still needs the fuel on the day after your lifts. Unless your exercise habits are extremely sporadic or a particular day is out of the norm (ie you’re normally sedentary but once a month you’ll go on a 10 mile hike), there’s no reason to deliberately vary your intake beyond what results from natural hunger levels.

3. Tracking exercise calories is difficult, time-consuming, and rarely accurate

You know the calorie burn amount that the elliptical or other cardio machine gives you? It’s wrong. Those machines lie, and the only thing you can say for certain is that the number is WAY too high. So if you’re eating back those calories, you’re automatically going to be eating too much. Non-cardio machines don’t even give you a calorie count to work from. And what about jogging, or biking, or “unofficial” exercise like going on a hike or playing a pick-up soccer game or just a particularly vigorous video game? You could spend your life googling calorie burns and tracking every minute of physical activity, but that would get old fast–and again, your calculations might be wrong. What’s the point of eating back exercise calories if the number isn’t even right?

4. Moreover, it steers you toward the wrong kinds of exercise

Which burns more calories, thirty minutes of lifting weights or thirty minutes on the elliptical? Well you don’t exactly know, but you do know that the elliptical tracks your calories–so that’s what you’re going to do. What’s more, it’s gotta be the second elliptical from the right in the third row at your campus gym, because that’s the one that gives the highest read-out. Obviously this line of thinking is silly, but it’s easily to fall into–especially when the number on the machine directly impacts what you get to eat that day. Most people OVERESTIMATE the number of calories they burn doing cardio, and UNDERESTIMATE the number of calories they burn strength training (Courtney at Barbells and Beakers has a number of great articles about this–here’s one to start out with). In reality, lifting weights burns almost as many calories per minute as cardio at the time, it increases your calorie burn throughout the day, and it raises your metabolism in the long run–yet many people prioritize cardio because they think it burns more calories.

5. It also causes discounts the importance of “unofficial” exercise

Tracking and eating back exercise calories can create the inaccurate mindset that ONLY officially designated and tracked exercise “counts,” and can lead people to discount or ignore non-gym physical activity–like the person who circles around the gym parking lot for 15 minutes looking for a closer parking space. In reality, your day-to-day activities–working an active job, raking leaves or shoveling snow, walking to and from class, cleaning the house, getting your groove on in the club–burn many more calories than you think, but it’s easy to forget about them when you’re only tracking “official calories.” So you skip a night out with friends in order to spend a hour on the treadmill, or complain that you don’t have time to shovel the driveway because you have to do your workout DVD, when in reality a night of dancing or intense shoveling would have burned just as many calories without neglecting your obligations or sacrificing your social life. (To see real data on how lifting, cardio, and day-to-day life affects calorie burn, check out The Calorie Burn Experiment at Foods of April. April’s blog was my number one inspiration for my current lifestyle, and really deserves its own post!)

6. It makes you think you can trade off food for exercise (or vice versa)

You’ve heard it a million times and it’s true: you can’t out-exercise a bad diet. Yes exercise enables you to eat more, but even someone who does hard labor and works out twice a day isn’t going to be burning more than twice their BMR. It takes over two hours of HARD exercise for most people to burn 1000 calories–but less than ten minutes to eat it, and unless you’re Lance Armstrong or Michael Phelps, there is no amount of exercise you can do that will let you eat whatever you want. Especially if you’re basing your calorie burn on the grossly over-exaggerated numbers given by the machine. (This is probably a big reason why starting an exercise routine, particularly a cardio-heavy one, can sometimes cause people to GAIN weight–because they significantly overestimate how much they can eat.) On the flipside, this mindset may lead people who don’t particularly enjoy exercise to think that they can skip it altogether and compensate by eating less, which won’t work either. As a generalization, diet is key for losing weight; exercise (especially weight lifting!) is key for maintaining your weight and becoming thinner, tighter, and more defined; both are essential for getting the body you want and you can’t just substitute one for the other.

7. Finally, tracking and eating back exercise calories can create a psychologically unhealthy relationship with food and exercise

This one is a little tricky. Some people benefit from directly associating exercise with caloric intake because it helps them develop a mindset of “Food is fuel,” which can be a good thing (although it’s problematic if that’s the ONLY purpose you see for food). But if tying calories to exercise fuels the attitude that exercise is punishment for food, or that you have to workout to “earn” your right to eat, that’s not a good thing. You get to eat because you’re a living, breathing human being, not because you spent X number of hours in the gym! This mindset can also lead people to spend hours working out to compensate for binges or what they see as unhealthy eating. This behavior is actually an eating disorder known as exercise bulimia (read more about it here) and it can lead to injuries and fatigue as well as bone, heart, reproductive and other problems down the line. (Not to mention that it likely won’t even work-see point 6!) And if you see exercise as a punishment rather than an enjoyable part of your lifestyle, it’s unlikely that you’ll stick with it and maintain your weight for life.


So does this mean you should NEVER eat back your exercise calories? That depends. If tracking and eating exercise calories has proved effective for losing weight and maintaining a healthy mindset, then it’s okay to stick to it–it’s all about figuring out what works for YOU! And if you find yourself consistently hungrier on days that you work out, it might make sense to calorie cycle based on your workout schedule even if you don’t officially track (For example, if you work out every other day and your daily calorie target is 1600, you might decide to eat 1800 calories on the days you work out and 1400 on the days you don’t.) There’s also nothing wrong with eating significantly more or less once in a while on days when your activity level is particularly out of the norm–ie you’re vacationing in a new city and spend a whole weekend exploring on foot, or you get the flu and are stuck in bed for a week. 

But if eating back exercise calories isn’t working for you: if you find difficult, time-consuming, or stressful; if it leaves you constantly hungry or overly full; if you’re not losing weight; if you recognize yourself developing an unhealthy attitude towards food and exercise, then it’s time to try something else. Even if you believe that eating exercise calories does work better for you, it’s still worth calculating your average daily needs based on BMR/activity level (which, again, I explain how to do here) to see how the numbers compare (and chances are that if eating exercise calories is working, than the numbers are fairly close).

Finally, if you’re absolutely set on eating back exercise calories, it might be worth investing in an calorie monitoring system such as BodyBugg or Bodymedia, which you wear on your arm 24/7 accurately track your calorie expenditure so you’ll know exactly how much you’re burning throughout the day. The only caveat is these tend to be pricey–they appear to run $100-200 online plus a $6-10 monthly subscription fee after the first 3-12 months. There may be cheaper alternatives out there, but just make sure you do the research and know what you’re getting (for example, most normal heart rate monitors won’t track calorie expenditure unless you’re working at over 75% of maximum heart rate).

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I hope this was helpful and free to pass it on! And as always, don’t hesitate to send me a message if you have any further questions! 🙂

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