Do you ever wonder about the accuracy of our "Tools"

Jenks

So I got into a conversation with the PT at my gym about calories in calories out, BMR and a bunch of other stuff. He pretty much questioned the integrity of the 'calculations' on a website based on our weight and height. He also wasn't to impressed with the calories out being tracked with an HRM he was like "well I guess it could measure how hard you're working".
So I decided to figure out how accurate my "tools" are, figuring my HRM would be the most accurate since it works off my heart rate.
My first experiment was to figure out my BMR, which under tools here on MFP is 1,429. So last night I went to bed with my HRM on. I let it run for 8 hours, 1 of those hours I was awake but just laying there, half a sleep for part of it even.
According to my HRM I burned 579 calories in 8 hours just sleeping/laying there, which would equal 1737 in a 24 hour period if I would just lay in bed all day.

Which according to MFP "Your BMR is how many calories you'd burn if you stayed in bed all day — basically, how many calories you burn just to stay alive."

Anyways, just thought it was interesting.

erickirb

HRM's are only more accurate than other methods when your heart rate is elevated not at rest, so the BMR calculator, which might not be exact, is probably better than using your HRM the way you described.

ladyofivy

Ummm I don't think that there are many people here who would think that any of the tools are 100% on for any person. It's an average for someone of that size and sex. For someone who is more fit, their heart rate will be higher, and thus will burn more calories. Seeing that you've already lost 42 lbs, it actually looks really accurate to me.

There's no "better" way to measure this for a general populous than what Mike has already done. He took the basic facts that he had at hand and used them for a general ruler for everyone.

I trust the accuracy as much as I trust the accuracy for the calories included in the food that I eat. I mean, if I am allotted 17 chips per serving, do they mean 17 of the largest chips in the bag, or do they mean 17 chips including some of the broken pieces counted as chips?

There's nothing that can ever be 100%. So I take everything at face value, and never expect it to be perfect. What I know is that I'm getting results from the imperfect system. That's what matters to me.

TCASMEY

Did the PT have a better way to get an idea of how many calories were being burned?

I don't trust my HRM for a 24 hour time. I wore mine once for 24 hours and it said I burned over 3000 calories. That was a non-workout day. If that were true I should be losing close to 1 pound a day. I think HRM are only accurate to the point they give you and idea how hard you are working and a general idea of how many calories burned!

Jenks

HRM's are only more accurate than other methods when your heart rate is elevated not at rest, so the BMR calculator, which might not be exact, is probably better than using your HRM the way you described.

hmmmm....ok. ty.

Jenks

Did the PT have a better way to get an idea of how many calories were being burned?

I don't trust my HRM for a 24 hour time. I wore mine once for 24 hours and it said I burned over 3000 calories. That was a non-workout day. If that were true I should be losing close to 1 pound a day. I think HRM are only accurate to the point they give you and idea how hard you are working and a general idea of how many calories burned!

The way he recommended to get your "true" bmr was to go to the hospital and get it tested....no thanks
But someone else said something about the HRM at rest as well.....oh well

Luckymam

I just use the 'tools' as basic guides. I certainly question the calorie allowance given for exercise. I tend to massively round it down as I think it's far too generous.

Clew

I just use the 'tools' as basic guides. I certainly question the calorie allowance given for exercise. I tend to massively round it down as I think it's far too generous.

Agreed ... it's a basic guide, to give the member a general ballpark. Since getting my HRM I've noted some are quite a bit lower than I actually expend, and some are a bit higher. Everyone's body is a different machine with different levels of "efficiency" as everyone else's ... so of course the tools' estimates aren't going to be spot on all the time. It's better than nothing though, if you have no other tracking method!

Thanks to the admins for all they've put into this site.

trackme

Well, I was pretty impressed with how accurate the exercise calories were....for 30 min of lawn mowing it said 195, my HRM said 212. For 1 hour of yoga, it said 180, and my HRM said 200. Not too bad since I really felt I was working harder in yoga! As far as the rest of the stuff, yeah who knows!

Happyguy

Lance Armstrong has a resting heartrate of around 20 but he needs as many calories to stay alive as the rest of us, probably more.

The HRM measures EFFORT more than OUTPUT. A strong heart will pump more blood with each beat so it will beat more slowly under the same load.

I just use the tools and it has worked fine. So far I've lost 34 pounds so if it's off it isn't hurting me much.

Caveat: I am not an expert and this is more of a semi-informed opinion than anything else.

erickirb

Ummm I don't think that there are many people here who would think that any of the tools are 100% on for any person. It's an average for someone of that size and sex. For someone who is more fit, their heart rate will be higher, and thus will burn more calories.

Actually it is the opposite, the more fit someone is the less calories they burn doing the same exercises. And the more fit you are the lower your heart rate becomes.

TropicalKitty

A lot of the numbers given for BMR and exercise are based off of "normal" people. You get a standard curve, make an equation, then extrapolate for weights/heights not specifically tested. Especially at the extremes, you are going to have deviations from the trendline.

One experiment with your HRM overnight isn't necessarily going to disprove the calculations on MFP. A lot of factors can go into your heart rate. I know there are nights I've woken up with my heart racing - adrenaline kick, dehydration, caffeine consumption...which could affect those numbers. Plus, cardiovascular health plays a big role in your resting heart rate.

I'm not trying to start a debate as to what could have caused your number to be what is was, but just to point out that it wasn't a controlled experiment, with a number of variables present. It's good to be aware that things aren't perfect and not to base everything off of them. I think this just really points to the obessesion with numbers we have as opposed to an overall health goal of eating reasonably and mindfully, and being active. No matter who you talk to, you can always find someone who says soemthing contradictory to what you think is right/wrong. Instead of casting all doubt on the BMR here or the HRM, take things with a grain of salt. You've obviously been doing well with the path you've been on to lose what you have!

TrainingWithTonya

The only way to accurately measure metabolic rates is through direct calorimetry. That requires locking you in a room that is specially designed to measure the amount of oxygen and carbon dioxide you inhale and exhale. Not exactly cost effective or comfortable. Second to that, you have indirect calorimetry, which is where you are on a bike or treadmill or whatever and are hooked up to a machine that you breathe through, which also measures the amount of oxygen and carbon dioxide. Also cost prohibitive and uncomfortable. Any other estimate, including the formulas used on MFP and numerous other formulas that we are taught as exercise physiologists, and heart rate monitors are all estimates. As part of my bachelors program in exercise physiology, I've actually been hooked up to the indirect calorimeter and MFP is as close as I've found to it online. I have another formula that I use from my studies that is a little more accurate, but it isn't that far off from MFP (like 100 calories).

As for your personal trainer, they don't know the specifics of calorie testing. I know this because I've been a certified personal trainer for 14 years. In certification, we're taught one way of doing it based on the specific certification we take. Most certifications teach based on ACSM guidelines, but they all tweek things to make their certification different then ACSM for trademark reasons so they pick different tests or formulas for their programs. I didn't realize just how much personal trainers didn't learn until I started my bachelors program. Now that I see what all I didn't know all those years, I wish there was some kind of regulation that all personal trainers have to have a degree. Seriously, now I know why ACSM requires at least a bachelors in an exercise field for their clinical certification.

Jenks

The only way to accurately measure metabolic rates is through direct calorimetry. That requires locking you in a room that is specially designed to measure the amount of oxygen and carbon dioxide you inhale and exhale. Not exactly cost effective or comfortable. Second to that, you have indirect calorimetry, which is where you are on a bike or treadmill or whatever and are hooked up to a machine that you breathe through, which also measures the amount of oxygen and carbon dioxide. Also cost prohibitive and uncomfortable. Any other estimate, including the formulas used on MFP and numerous other formulas that we are taught as exercise physiologists, and heart rate monitors are all estimates. As part of my bachelors program in exercise physiology, I've actually been hooked up to the indirect calorimeter and MFP is as close as I've found to it online. I have another formula that I use from my studies that is a little more accurate, but it isn't that far off from MFP (like 100 calories).

As for your personal trainer, they don't know the specifics of calorie testing. I know this because I've been a certified personal trainer for 14 years. In certification, we're taught one way of doing it based on the specific certification we take. Most certifications teach based on ACSM guidelines, but they all tweek things to make their certification different then ACSM for trademark reasons so they pick different tests or formulas for their programs. I didn't realize just how much personal trainers didn't learn until I started my bachelors program. Now that I see what all I didn't know all those years, I wish there was some kind of regulation that all personal trainers have to have a degree. Seriously, now I know why ACSM requires at least a bachelors in an exercise field for their clinical certification.

Thank you for letting me know your experience with the testing and the results compared to MFP.

LotusF1ower

Ummm I don't think that there are many people here who would think that any of the tools are 100% on for any person. It's an average for someone of that size and sex. For someone who is more fit, their heart rate will be higher, and thus will burn more calories. Seeing that you've already lost 42 lbs, it actually looks really accurate to me.

There's no "better" way to measure this for a general populous than what Mike has already done. He took the basic facts that he had at hand and used them for a general ruler for everyone.

I trust the accuracy as much as I trust the accuracy for the calories included in the food that I eat. I mean, if I am allotted 17 chips per serving, do they mean 17 of the largest chips in the bag, or do they mean 17 chips including some of the broken pieces counted as chips?

There's nothing that can ever be 100%. So I take everything at face value, and never expect it to be perfect. What I know is that I'm getting results from the imperfect system. That's what matters to me.

No on the contrary, the fitter you are the slower your heartbeat. Some world class runners have heartbeats around 40 bpm. They will burn more calories because they will have less fat, but more muscle, muscle burns more calories see.

It's okay I wasn't trying to pick holes, just wanted to put it straight about the heartbeat though xxx

stormieweather

I had my metabolism tested by a lab (breathing oxygen into a machine). My RMR was 1800 which they said was 25% higher than 'average'. Based on the Mifflin - St. Jeor calculation (and MFP), my RMR should be 1397. BMR and RMR are slightly different, but not significantly. This means that MFP is dead on with it's calculations, although there is no way for it to know I burn at a 25% faster rate than others.

1,397 x 25% = 349 +1,397 = 1,746

Additionally, as 20% of my RMR is 1,440, this is the bare minimum I should eat to lose weight. Anything less than that is considered a VLCD (semi-starvation) and should be done only with a doctor's supervision (per the lab/dietician/trainer who tested me).

The point is that one size does NOT fit all, but that MFP is pretty darn accurate, on average.


More info on calorieis you burn - http://www.caloriesperhour.com/tutorial_BMR.php