Thoughts on Measuring Caloric Burn
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Aaron_K123
Posts: 7,122 Member
I had someone message me to give an opinion on measuring calorie burn. I told them that what I was going to say was my opinion and that I might be wrong and they should look at other sources as well. After writing them an answer I thought maybe I should just post it on the forum and let people pick it apart for inaccuracies if they wanted to.
So...the following is a mix of my understanding and my opinion, if I've said something that is false point it out. So with that said here it is:
In my opinion any machine-based estimate of calories burned should be doubted a bit. There is one way to accurately measure caloric burn and it is the way athletes do it which is to go into a clinic and be hooked up to a machine that measures the amount of oxygen and CO2 you exchange. Your metabolism breaks down hydrocarbons into water and carbon and that carbon is expelled from your body in your breath (this by the way is where the weight goes when you lose fat, out your mouth in the form of breath). This machine measures your CO2 output by measuring the volume of oxygen you exchange much like you could hook a smog detector up to a car and measure its output.
Of course that technique is not practical for us day to day. It was noted that another indicator of how "hot" your metabolism is running is your heart rate. As your body processes more hydrocarbons the CO2 is shuttled to your lungs by your blood and if you burn more you produce more and your blood has to move faster so your heart pumps faster. So heart rate loosely correlates with C02 exchange which is directly linked to your metabolism which is linked to calories burned.
So what does that do for us. Well if you monitor your heart rate you can get some idea of how many calories you are burning. Thing is heart rate doesn't perfectly match up to CO2 exchange but it can be somewhat corrected based on other info like how large you are (weight) and what range between minimum and maximum heart rate you are at. There are certain "zones" of heart rates and a narrow band of the aerobic range is where heart rate monitors that convert to calories burned are tuned to.
What that means is that in an ideal situation where you have a heartrate monitor that you've told what your weight is, what your minimum heart rate is and what your maximum heart rate is AND you are in that specific aerobic range and holding steady for duration then a heart rate monitor gives a good approximation of calories burned.
Problem is with gym machines is most of them just measure your heart rate (if that) to estimate calories burned but know nothing about you...what your weight is, what your min and max heart rate is, so they tend to be off. Not only that but most people don't just stay in that specific aerobic range...they dip in and out of it which makes the accuracy again sort of waver around. A 45 minute treadmill run might have you in that range for only 30 minutes especially if you are changing your pace.
So...if you have an HRM that you can program, has a chest strap so it is accurate in measuring your heart rate AND you are in steady state cardio for your aerobic range (which is basically you can still talk but you are panting a bit) that is practically the best estimate you can have. If you go off a gym machine reading chances are its going to overestimate your burn but its hard to say by how much.
A rule I go by myself is just the idea that no matter how hard I push myself I am never going to burn more than 10-12 calories per minute so if I get an estimate that says I burned 1000 calories in an hour I don't believe it and cut it in half or at max put it at 600 cal. That is for my heart pounding out of my chest for almost full duration. This is specific to me though and can of course vary.
Now. About weight lifting or HIIT. Any exercise that has you doing maximum intensity for brief periods of time and then resting is likely anaerobic not aerobic in nature. Not only that but it causes your heart rate to quickly spike and then quickly drop. As a result of this a HRM will be absolute crap and estimating calories burned. Because of that there is no good practical way that I am aware of to measure caloric burn while doing weight training or HIIT. What I do personally is I just act like it was cardio then divide that burn by 2. So if I do an hour of weight training where if I had been doing cardio I would have burned 600 calories I put in that I burned 300. I do think though there are some resistance training methods, like circuit training, where you go from move to move without rest that actually keep your heart pumping and probably are closer in approximation to true cardio.
In your specific example of 300 calories for 30 min of elliptical I think that is actually quite possible provided that you were pushing yourself and your heart beat was quite high. I don't know what your min and max heart rate is but I'd imagine if you were holding at say 170 bpm for 30 min then it would be that high. Thing is if you started cool and did it for 30 min then that first 10 min would basically be warming up to it and would not be burning much so it'd be more like 20 min of steadystate cardio. Frankly it is just hard to say. So many people on this site end up just eating back half their estimated burn because of that. I essentially do that myself since I tend to assume most measurements are overestimates and as a result I scale back what I eat back.
So...the following is a mix of my understanding and my opinion, if I've said something that is false point it out. So with that said here it is:
In my opinion any machine-based estimate of calories burned should be doubted a bit. There is one way to accurately measure caloric burn and it is the way athletes do it which is to go into a clinic and be hooked up to a machine that measures the amount of oxygen and CO2 you exchange. Your metabolism breaks down hydrocarbons into water and carbon and that carbon is expelled from your body in your breath (this by the way is where the weight goes when you lose fat, out your mouth in the form of breath). This machine measures your CO2 output by measuring the volume of oxygen you exchange much like you could hook a smog detector up to a car and measure its output.
Of course that technique is not practical for us day to day. It was noted that another indicator of how "hot" your metabolism is running is your heart rate. As your body processes more hydrocarbons the CO2 is shuttled to your lungs by your blood and if you burn more you produce more and your blood has to move faster so your heart pumps faster. So heart rate loosely correlates with C02 exchange which is directly linked to your metabolism which is linked to calories burned.
So what does that do for us. Well if you monitor your heart rate you can get some idea of how many calories you are burning. Thing is heart rate doesn't perfectly match up to CO2 exchange but it can be somewhat corrected based on other info like how large you are (weight) and what range between minimum and maximum heart rate you are at. There are certain "zones" of heart rates and a narrow band of the aerobic range is where heart rate monitors that convert to calories burned are tuned to.
What that means is that in an ideal situation where you have a heartrate monitor that you've told what your weight is, what your minimum heart rate is and what your maximum heart rate is AND you are in that specific aerobic range and holding steady for duration then a heart rate monitor gives a good approximation of calories burned.
Problem is with gym machines is most of them just measure your heart rate (if that) to estimate calories burned but know nothing about you...what your weight is, what your min and max heart rate is, so they tend to be off. Not only that but most people don't just stay in that specific aerobic range...they dip in and out of it which makes the accuracy again sort of waver around. A 45 minute treadmill run might have you in that range for only 30 minutes especially if you are changing your pace.
So...if you have an HRM that you can program, has a chest strap so it is accurate in measuring your heart rate AND you are in steady state cardio for your aerobic range (which is basically you can still talk but you are panting a bit) that is practically the best estimate you can have. If you go off a gym machine reading chances are its going to overestimate your burn but its hard to say by how much.
A rule I go by myself is just the idea that no matter how hard I push myself I am never going to burn more than 10-12 calories per minute so if I get an estimate that says I burned 1000 calories in an hour I don't believe it and cut it in half or at max put it at 600 cal. That is for my heart pounding out of my chest for almost full duration. This is specific to me though and can of course vary.
Now. About weight lifting or HIIT. Any exercise that has you doing maximum intensity for brief periods of time and then resting is likely anaerobic not aerobic in nature. Not only that but it causes your heart rate to quickly spike and then quickly drop. As a result of this a HRM will be absolute crap and estimating calories burned. Because of that there is no good practical way that I am aware of to measure caloric burn while doing weight training or HIIT. What I do personally is I just act like it was cardio then divide that burn by 2. So if I do an hour of weight training where if I had been doing cardio I would have burned 600 calories I put in that I burned 300. I do think though there are some resistance training methods, like circuit training, where you go from move to move without rest that actually keep your heart pumping and probably are closer in approximation to true cardio.
In your specific example of 300 calories for 30 min of elliptical I think that is actually quite possible provided that you were pushing yourself and your heart beat was quite high. I don't know what your min and max heart rate is but I'd imagine if you were holding at say 170 bpm for 30 min then it would be that high. Thing is if you started cool and did it for 30 min then that first 10 min would basically be warming up to it and would not be burning much so it'd be more like 20 min of steadystate cardio. Frankly it is just hard to say. So many people on this site end up just eating back half their estimated burn because of that. I essentially do that myself since I tend to assume most measurements are overestimates and as a result I scale back what I eat back.
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Replies
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I think the machines and gadgets tend to be on the high side of calories burned so I log all of it but only eat back some.0
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I've been wearing a bodymedia fit link for two weeks. I set it up for a deficit of 500 calories per day average to lose half a pound per week. So far, it's right on the money (science is cool)! I burn way less than I thought!
I also take atenolol for my heart rate. Yes, I could be thinner more easily without it, but I really want to live longer! I also started taking a new med for my fibromyalgia which just slows EVERYTHING down in my body.
There are just so many different things that determine how many calories you burn in a 24 hour period.0 -
Your metabolism breaks down hydrocarbons into water and carbon and that carbon is expelled from your body in your breath (this by the way is where the weight goes when you lose fat, out your mouth in the form of breath).
Thinking about this is going to make my afternoon walk much funnier to me. I will be imagining blowing my fat out of my mouth with each breath. --Ooo! I'm seeing the title of your new book, Aaron: "Breathe Yourself Thin." You can acknowledge me on the dedication page.
PS I wish I had some real insight to add, but as usual, I'll just make jokes and be off. Thanks for this!0 -
I usually do 10 minute warm up - cardio then 50 mins or so hard weight lifting the 20 mins hit cardio - my HRM always calculates 700 or so cals... I always cut this in half and upload it MFP. This seems to work for me -0
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This is a good common sense post!
It took me a long time to finally understand that HRM's are only good for steady-state cardio and nothing more . Weight Training is a whole different animal and your "rule of thumb" for calories is a good way to go about it. The "long term" gains from weight training are immeasurable.. but we all know that!
Like I always say... it is better to "overestimate" what you eat and "underestimate" what you burn! :drinker:0 -
Your metabolism breaks down hydrocarbons into water and carbon and that carbon is expelled from your body in your breath (this by the way is where the weight goes when you lose fat, out your mouth in the form of breath).
Thinking about this is going to make my afternoon walk much funnier to me. I will be imagining blowing my fat out of my mouth with each breath. --Ooo! I'm seeing the title of your new book, Aaron: "Breathe Yourself Thin." You can acknowledge me on the dedication page.
PS I wish I had some real insight to add, but as usual, I'll just make jokes and be off. Thanks for this!
hah hah yeah. Before anyone goes around hyperventilating to lose weight remember that what actually matters is the amount of C02 you expel. If you exercise there is more CO2 to get rid of so you breath heavy. If you just breath heavily on purpose for no good reason you will still breath out the same amount of CO2 you will just breath out less of it per breath. So yeah hyperventilating is not going to do a thing.0 -
Your metabolism breaks down hydrocarbons into water and carbon and that carbon is expelled from your body in your breath (this by the way is where the weight goes when you lose fat, out your mouth in the form of breath).
Thinking about this is going to make my afternoon walk much funnier to me. I will be imagining blowing my fat out of my mouth with each breath. --Ooo! I'm seeing the title of your new book, Aaron: "Breathe Yourself Thin." You can acknowledge me on the dedication page.
PS I wish I had some real insight to add, but as usual, I'll just make jokes and be off. Thanks for this!
Also think about where people thinks it goes without knowing. Even funnier.
http://youtu.be/NGKLpYtZ19Q 0 -
Your metabolism breaks down hydrocarbons into water and carbon and that carbon is expelled from your body in your breath (this by the way is where the weight goes when you lose fat, out your mouth in the form of breath).
Thinking about this is going to make my afternoon walk much funnier to me. I will be imagining blowing my fat out of my mouth with each breath. --Ooo! I'm seeing the title of your new book, Aaron: "Breathe Yourself Thin." You can acknowledge me on the dedication page.
PS I wish I had some real insight to add, but as usual, I'll just make jokes and be off. Thanks for this!
Also think about where people thinks it goes without knowing. Even funnier.http://youtu.be/NGKLpYtZ19Q
Nice video explanation, good find.0 -
A rule I go by myself is just the idea that no matter how hard I push myself I am never going to burn more than 10-12 calories per minute so if I get an estimate that says I burned 1000 calories in an hour I don't believe it and cut it in half or at max put it at 600 cal.
I'm curious why you think that. Not necessarily challenging, but wondering whether there's evidence for that assumption. Obviously, it's very conservative, so it's better to think that way if your intention is to lose weight, but the flip side would also be true. If you're optimizing for training, though, you may be short on nutrition.
I do most of my exercise work on the erg - many days I'll do an hour of steady state rowing, averaging 2:10-2:15 splits, resulting in an average HR of about 160-165 (ranging from 130 in the early part of the piece to 175-180 by the end, depending upon how many faster pieces I'll do to keep me from getting bored. That average is about 90% of my VO2max, and it winds up calculating at around 1100-1200 calories burned (not net). Similar sort of workout to what you describe.
All of the different formulae give roughly the same result for that load and my size, so I'm curious why the assumption that such a result is off by a factor of almost 2.
Greg0 -
A rule I go by myself is just the idea that no matter how hard I push myself I am never going to burn more than 10-12 calories per minute so if I get an estimate that says I burned 1000 calories in an hour I don't believe it and cut it in half or at max put it at 600 cal.
I'm curious why you think that. Not necessarily challenging, but wondering whether there's evidence for that assumption. Obviously, it's very conservative, so it's better to think that way if your intention is to lose weight, but the flip side would also be true. If you're optimizing for training, though, you may be short on nutrition.
I do most of my exercise work on the erg - many days I'll do an hour of steady state rowing, averaging 2:10-2:15 splits, resulting in an average HR of about 160-165 (ranging from 130 in the early part of the piece to 175-180 by the end, depending upon how many faster pieces I'll do to keep me from getting bored. That average is about 90% of my VO2max, and it winds up calculating at around 1100-1200 calories burned (not net). Similar sort of workout to what you describe.
All of the different formulae give roughly the same result for that load and my size, so I'm curious why the assumption that such a result is off by a factor of almost 2.
Greg
Honestly I don't have a very good reason. Having never been an athlete in a sport I've never had my VO2-max measured. When using an HRM I tend to assume that it miscalculates outside of my aerobic range (either if I am over or under) and during intense exercise I'm often over my aerobic range (P90X plyo is 55 min long and I'm in my "range" for about 22 of those minutes because I'm above it most of the time). During that plyo my HRM says I burn 980 calories but assuming its an overestimate I bump that down to 600. Then decided that 600 would be my limit for 1 hour of activity essentially. I remember reading somewhere that 10 cal/min was a typical max burn for someone my size and age. I know, horrible to be so vague but I honestly don't remember so the best I can do is say that yeah maybe that is B.S.
You are basically right that I am doing that because my goal it to lose weight and I'd rather be a bit under than a lot over on my deficit. Ideally I'd be spot on my deficit but I just don't trust an HRM to give a truly accurate read (even though its the best we practically have).
You very well might be correct that I am underestimating as a result, I suppose it is not impossible that I am burning more than 600 an hour.0 -
Don't need a VO2max test to get a great estimate.
I've been using the method in the following link on people that have posted their VO2max data, and they usually give their speed/incline/weight, ect, to see how it matches up - so far within 5% - except when you go in to anaerobic mode.
And the nice thing with this test, you can get formula for non-steady state, and steady state type workouts.
http://www.myfitnesspal.com/blog/heybales/view/getting-your-personalized-calorie-burn-formula-6636250
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