The Most Accurate Way to Measure Your Metabolism

By , SparkPeople Blogger
If you're like most people who are struggling to lose weight, you've started watching what you eat and counting (and cutting back) on your calories. We all know that weight loss is the result of a simple equation: burning more calories than you take in each day. But how do you know how many calories you REALLY burn—or how many calories you should be eating for optimal weight loss?
We all have our own unique metabolic rates—the amount of calories our bodies use just to stay alive; this is called your resting metabolic rate (RMR). Even at total rest—and without moving—your body is using ("burning") calories just to breathe, circulate blood, digest food, think, blink and more. This actually takes more calories than you might think—hundreds or even thousands. On top of your RMR, even if you don't work out, you burn additional calories by performing basic activities of daily living: brushing your teeth, typing on your computer, and driving your car.
When you visit most nutritionists, sign up for a free weight-loss plan at, or even follow a diet plan you read about in a book or magazine—you're getting some good estimates of your calorie needs, usually based on your weight, gender and possibly your age and height. But these widely used formulas are just that—estimates. They are reasonably accurate for a lot of people, but they are not always accurate for everyone. "Calorie Plan A" may be too few calories for you but be perfect for your sister to lose weight. "Calorie Plan B" might not cut calories enough, yet be too many calories for your friend who weighs the same amount you do. Since we are all unique, estimates don't always work. And when they don't, it can stall your weight loss or bring it do a grinding halt despite your efforts of tracking, counting, measuring and eating within a specific calorie range.

"There are a few people who really struggle in determining their accurate weight-loss calorie range," says SparkPeople's head dietitian, Becky Hand, RD, LD.  "They just don't seem to 'fit' the standard formulas, and 'experimenting' with their calorie intake brings about more and more frustration."
So what's a person to do? You can tweak your plan, adding or cutting back on calories to see how your body responds. This is what a lot of people do throughout their journeys until they find the magic number that starts peeling away the pounds. It takes guessing, checking—and time. And it can work.
But there is another option: You can take a simple test to find out exactly how many calories you're burning each day. This eye-opening RMR test is non-invasive, takes a few minutes of time, and is pretty widely available for a fee. I recently tried it myself along with two SparkPeople employees, Jeff and Jaime, both of whom have been struggling to lose weight.
The test uses a device called the MedGem (similar RMR tests go by other names, such as "New Leaf").  According to Becky, "These hand-held indirect calorimetry devices can help provide another vital piece to solving their weight loss puzzle." You'll find these tests available in many health and fitness clubs, doctor offices, training facilities and weight-loss clinics. While some might offer tests as part of a weight-loss or training package, others offer the test on its own for a fee, which can range from as little as $50 to $100 or more.

Dawn Weatherwax, RD, CSSD, LD, ATC, CSCS, is a registered dietitian, athletic trainer and certified personal trainer who specializes in nutrition and fitness plans for both competitive and recreational athletes. She recently invited SparkPeople to check out her Sports Nutrition 2 Go facility in Liberty Township (just outside Cincinnati) to try the MedGem test, which normally costs $65 per person at her facility.
So How Does a MedGem Metabolism Test Work?
The MedGem is an easy-to-use, handheld device that accurately measures oxygen consumption (VO2) to determine resting metabolic rate (RMR)—the number of calories your body burns at rest. Knowing your RMR helps you understand your unique metabolism so you can develop a personalized plan to reach your goals.
The MedGem itself is basically a mouthpiece that you breathe into through your mouth while your nose is plugged. It takes about 10 minutes. It's neither uncomfortable nor difficult to do—you just sit still and breathe. The machine is hooked up to a computer that measures how much oxygen you use, which its software uses to determine your metabolic rate.

How to Get Accurate Metabolism Testing Results
When you prepare for an appointment, you have to follow this protocol for the most accurate reading:
  • Do not consume any food for 4 hours prior to your appointment.  
  • Do not consume any caffeinated beverages (i.e. coffee, soda, energy drinks, etc.) for 4 hours prior to your appointment.  Sipping on water is OK.
  • Do not perform any strenuous physical exercise (i.e., vigorous running, strength training, etc.) for 4-hours prior to your appointment.
  • Abstain from all tobacco products for 1 hour prior to your appointment.
  • Continue taking all prescribed medications as indicated.

We chose an early morning appointment to make it easiest to stick to these guidelines.

Our Results
Here's a chart of our results. I'm sharing our heights, weights (as taken that day), and ages as well so you can see how each of our metabolisms compare given those differences.
Name Age Height Weight RMR Result
Jaime (F) 35 5'5" 182 2,190 calories
Jeff (M) 42 5'6" 247 2,230 calories
Nicole (F) 29 5'8" 145 2,410 calories

I was particularly fascinated in how we all have very different body sizes yet our RMRs were within just a couple hundred calories of one another. I would have assumed that people who had more fat mass would have much slower metabolisms, and that would be one of the big reasons that they struggle with their weight. But at least as far as the three of us are concerned, we're all pretty close to one another, assuming we all got accurate results.

What I can say for sure is that all of us were pretty close in actual "lean" (non-fat) body mass, based on other tests we did that day. So regardless of how much fat each of us carries, Jaime and I, for example, were within 1 pound of each other in our lean mass, and Jeff had about 30 pounds more of lean mass than each of us. These results seem to make sense to me considering those other facts--but I'm no expert in this field of testing either.

So How Accurate Are These Results?
According to Becky, "Recent studies indicate that for 'healthy' adults, these hand-held, easy to use,  indirect calorimetry devices provide similar results when compared to the more expensive, and more cumbersome large cart equipment that also requires careful calibration and isn't widely available." Current studies are now investigating their accuracy with specialty populations such as older adults, children, hospital patients on vents, and the malnourished, she explains.

Of course, a person's activity level adds another level of calorie burning on top of this.  The more active you are throughout the day (taking the stairs, walking around, etc.) and the more you exercise—the higher your body's calorie needs will be.
So What Does This Mean for Weight Loss? How Do You Use This Information?
Having witnessed the results of more than 3,000 metabolic tests, Dawn has noticed quite a few trends. Her first step is comparing the result of test with the amount of calories a person actually eats. If a person is eating more than they burn, then the issue is clear: They are simply eating too much and need to cut back.
But more often than not, individuals who have been eating far less than their RMR but still aren't losing weight can mean one of two things, according to Dawn:
  1. They are actually eating far too little. She's seen it more times than she can count, both in overweight individuals and in people who only have another 5-10 pounds to lose. When a person consistenly eats too little, your metabolism can lower, mainly because you can't "give your all" to your daily life or your workouts. In these cases, she advises people to slowly increase their calorie intake by a hundred calories a week until they find that "sweet spot" where they have more energy, feel better, and allow their bodies to let go of some of its body fat.

    My co-worker Jaime thinks this may explain why she has struggled to lose weight even though she exercises five days a week and maintains a calorie-controlled diet. "I now understand why my body has not been losing fat as quickly as I had hoped despite all my efforts," she said after the test. "I essentially was not fueling my body enough (eating around 1,200 calories a day) for it to feel comfortable with letting go of fat! I’m now working on increasing my daily calories to 1,600 on non-workout days and just over 1,800 calories on the days I do exercise."
  2. There are underlying medical or hormonal issues interfering with their weight loss. Hormonal imbalances, such as low testosterone or thyroid issues, can affect your weight as well, says Dawn. "If a person is eating within an appropriate range for weight loss but is gaining weight or not losing weight, hormones may be to blame," she says. When the numbers simply don't add up, she advises that people get a full hormone profile at their doctor to see if anything is out of whack. Often, getting those hormones back into their healthy, normal ranges (via medical intervention) can be just the ticket to speed up weight loss. "Low testosterone is more common than you might think—in both men and women. So is a low-functioning thyroid," she explains.

    Jeff has been eating within a reasonable calorie range for weight loss without getting results—but he does have thyroid problems and realized he may need to check-in with his doctor and see about increasing his medication. "Since I have hypothyroidism, this will prove invaluable information to have while undergoing my other routine medical testing," says Jeff. "I think this is a great baseline for trying to kick-start my weight loss quest again. Knowing how many calories my body burns each day, and being able to use SparkPeople's free Fitness Tracker and Nutrition Tracker to calculate calories in and out should give me a great idea of how well I’m doing at burning calories and losing fat."

For the cost of the test, I think this is a worthwhile investment, especially if you've been on a long-term plateau or are truly doing "everything right" but not seeing progress. Most of these tests are administered by dietitians, fitness professionals, doctors and other wellness providers who are trained and capable at interpreting the results and offering valuable advice on how to use the results to reach your goals, although working directly with a licensed and/or registered dietitian would be ideal. To find a location near you that offers MedGem metabolism testing, click here.
"The whole experience was extremely valuable in helping me understand my caloric needs with the current condition of my body, but more importantly helped me 'reset' in my mind what I need to focus on moving forward," says Jaime.
Jeff had a great experience as well, both as a jump-start to get him focused on the right things to lose weight and to better understand how his body uses calories. "I was surprised to learn how many calories his body uses just standing still and not doing anything," he commented.
Thanks again to Dawn Weatherwax and Sports Nutrition 2 Go for letting us try the MedGem metabolism test! Stay tuned for a follow-up blog about another fun and interesting test we tried during our visit.
What do you think about the MedGem test? Would you try it? Have you ever had your metabolism tested?

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I had this test done when I was noticing the easy weight gain, my metabolism is very low, 1600 calories a day, due to an illness and losing some muscle mass. Which meant that even eating even an extra 100 calories was way too easy. I have worked on building muscle and tried to be consistent with eating a lot of fruits and veggies...filling up on them instead of starchy or sugary treats. I have lost weight very slowly, but hey, guess what? I haven't gained. Knowledge is power Report
now where can I get one in my city... Report
Interesting ... I am not sure I am sold that this will give an accurate reading, but it is good to see it is being realized that not all people do burn the same amount of calories. Soooo many times I have all but been called a lier from drs when discussing weight loss. I would not loose by their method or "diet" and they would simply blame me for not following when I was extremely faithful and counted every calorie and measured everything that went into my mouth. Report
Thanks for posting this! funny thing is I just did this test and hydrostatic testing today (wednesday) and i blogged about it too! check it out! :) Report
Quite a comprehensive summary. I was not aware of this test. Report
Encouraging article... Thanks!! Report
I had a frustrating experience a few summers ago. I was working out in the morning and doing cardio kickboxing a couple nights a week. But I didn't lose any weight. I guess I was not getting enough calories...Unfortunately, there are no sites in my area to have this test :( Report
Booo, the only place listed near me that does it, is no longer in existence :( Report
Oh my gosh! I did a zip code search and discovered that the dietitians in the hospital where I work can perform this test! I am definitely intrigued and if I can swing it financially will have this testing done. Knowledge is power! Report
Every doctor I have been to in the past fifty years is bound and determined I have thyroid problems because no matter what dietitian they sent me to or what program they gave me, I could never lose weight,,
One summer I would consume about 4500 calories a day, not trying to lose, just pigging out, I was slimmer then,, I took iron pills, nothing else,, as long as I took those iron pills, I could eat virtually ANYTHING in any amounts, and the next day I would weigh myself and had lost a minimum of three pounds!! Overnight!!!
I lost fifty five pounds in three months, eating anything that got in front of me,, like at one sitting, I ate a whole party pizza, an order of onion rings, a pitcher of pop, a banana split!! Next morning I lost one pound!! Crazy,,
My metabolism is, and I quote about ten doctors, "The craziest thing I have ever seen!" Now I munch a big salad, water, and lose nothing..
If I could afford this test, I might take it.. all things should only be guidelines however,, no science is perfect or exact...
If it is accurate, it could be a great tool for medical professionals... Report
I think that part of most people's "problem" is that they think they need to eat very little in order to lose weight. Many people aim for around 1200 calories a day, having heard that that's what dieters do. This article basically says that you DO have to eat more than that to lose weight (in most cases). I know that when I don't eat enough it definitely slows down my progress!

If you're able to have this kind of testing, and then adjust your calorie intake, etc., it may be just the push you need - especially if you're on a plateau. The testing itself is just a way to find out that starting number. Ends a lot of guessing, since most calculations are based upon standard figures. Report
What I would have found an interesting comparison is whether the RMR that SP would have calculated for those three individuals was more, less, or in the same range. There's really no value to spending $50 to $100 to get a more accurate number if the variation was within a couple hundred.

Believe me ... I'm a math geek to the core. I have a spreadsheet on which I calculate my BMR from 4 common formulae, 2 based on LBM, and then average them, multiply for sedentary activity, add my calculated calorie burn and see how closely on target to my 500 calorie deficit the result is.

But I'm a miser with money. I want to really see a value before I spend. In a scenario where fitness calories burned is an approximation, the likely amount of variation from the results of the formulae and this test don't seem particularly significant. (I say fitness calories burned are an approximation because when I put 30 minutes of "Stationary Bicycle, greater than 15mph" I will get the same calories burned whether I pedaled 16 mph at 1 resistance or 22 mph at 10 resistance. Obviously I would burn more calories with the latter.) Report
A couple comments:

"But more often than not, individuals who have been eating far less than their RMR but still aren't losing weight can mean one of two things, according to Dawn"

I think there is a third "thing" that needs to be considered: inaccurate tracking of food. I bring that up because I know from personal experience how easy this is to mess things up. And while I used to BADLY underestimate how much food I was eating, I'm sure it goes both ways.

Having said that, once I do hit my goal weight (4.6 pounds away!), this could be a very useful test to have. Thanks for share Coach Nicole! Report
You can also get a pretty good estimate of your total calorie burn for free by counting your calories and watching what the scale does...

Details here:


This method takes a lot of tracking and some basic spreadsheet skills, but what I like about it is that it adjusts over time as my activity increases or decreases, I eat more or less, etc.

So you can kind of watch what's going on and adjust accordingly.
I have never had this test and I wish I could afford it. My metabolism has been screwed up since my second round of chemo - 1 1/2 years ago!!!
I know it will bounce back - dr says so but I hate waiting Report
Wow, this sounds great. I just followed the link and found they do the testing at my community college which I attend 3x a week. Awesome. Report
I had the impedence test done at my gym ( with electric current). I was told that most women have between 80 and 100 pounds of muscle, I am 120 pounds of muscle. And that I should be eating about 1700 calories a day. I go to spin class twice a week, walk, jog, ride my bike...and the scale was not moving. When I eat a little more, I lose weight. Reading books such as those by Gary Taubes indicate it is NOT always the calories in, calories out. The more info we have the better IMHO. This article and comments show it is so important not to judge someone on their size. They may be doing all the "right things" and still not getting the results they want. And how awesome is that that they keep at it. But how much more awesome to have another piece of the puzzle that might get them closer to their weight loss goal. Report
I am so glad to see that Spark published this article.
I have been tested and it showed that my metabolism was so low it was a wonder I was losing any weight. I don't have a thyroid ,am on medication for that. I was working out 5 6 days a week . Eating 1200 calories a day and not losing.
Was put on medication to raise metabolism and with in 2 months had raised the metabolism. But still had more to go. Then I raised my calories to 1400 a day and that was the trigger I needed.
I get tested every 6 months . It is part of the weight loss plan I am undergoing through Legacy Hospital. Report
I strongly DISAGREE with the recommendation that these types of tests are worth the money spent. The fact that all 3 people were within a few hundred calories of each other, despite age, height, weight, gender, and underlying medical and hormonal issues actually proved to me that the testing DOESN'T give significant additional information. And I am both a physician AND a "numbers person" - I normally track everything, wear a heart rate monitor, believe any additional knowledge is power...
In this case, use the money to buy more fresh vegetables or invest in a new pair of running shoes - THAT would be a MUCH better investment! Report
I'm doing metabolic testing at the gym. My caloriepoint as well as cardiopoint. I hope to use this information to lose the last 15lbs. Report
I did this test several years ago, and was given about 1700 calories as my RMR. I even thought that might have been high since I wasn't as relaxed as I should have been. Also, I didn't know about not eating before hand, I probably did eat. I was about 40 years old, and 5'5". Now, I'm 50 years old, I wonder what it would be? I'm sure lower... Report
What an interesting blog with lots of great info! It's a good reminder that, try as we may to lose weight, we may not have all the information we need to balance caloric intake and exercise regimens and get the healthy results we want. Thanks, Coach Nicole! Report
I had the New Leaf testing done about 3 years ago when I was training for my first marathon. My RD wanted to ensure that I was eating enough to support my running performance, but not so much that I would start packing on the pounds. I think any time we have feedback, it helps personalize what we need to do that is best for us individually! Report
This really gets me wondering about people who grew up with asthma, like myself. I've noticed, particularly when I'm just sitting at my desk at work, that I don't breathe very often or very deeply. I think it comes from growing up with asthma and spending so many years being afraid to take a deep breath. It might make for interesting research to find out if adults who grew up with moderate or severe asthma have a tendency to have lower metabolism due to lower oxygen intake than normal adults. Report
GREAT BLOG! Love this so much. It's so important to understand RMR. So many people take it for granted. But its often the secret to weight loss and maintenance. Prayerfully, I can have this test done soon. Report
How I measure my metabolism is different and it gives me good real world results for free. What I do is simply eat less, track all my food, and see how the weight lost matches up to the calories consumed. The number I get is spot on with Sparkpeople's estimates most of the time. The biggest factor to consider is how active I've been throughout the day. Report
This is exactly what I need! I've lost 50 lbs on SparkPeople but have been stuck at this weight for about 3 months. I am a workout horse, logging well over 1000 minutes of exercise a month which includes aerobic and weight training. And I closely monitor my eating. I am going to see if I can find some place local to take this test. Report
While it would be nice to go through such a thing, availability and cost is probably going to be an issue for most people. You can go to websites (google: Basal Metabolic Rate) and get similar results. Maybe it's not perfect, but close enough. And really....sometimes I think we make it more complicated than it is. Portion Distortion, Over Availability of Junk Food, Stress to go with it, Money in our Pockets...This is America's problem more than knowing what our BMR is. I bet if we all knew what our rate was, the vast majority of us would still be battling the bulge. All comes down to discipline no matter how you add it up. Report
I actually just had a metabolism test done yesterday. It was a different type of device, using an electrical current through your body (and I have yet to google to find out how accurate those are). I'm currently 5' 0.5" and 232.8 pounds, and It listed my RMR at 1807. I always suspected my metabolism was absolute crap, but now that I've seen a few numbers to compare it to, I know for sure that I need to do everything I can to boost it up! Report
I would definitely try this. Report
I was surprided to find that there is one location only 20 miles from me in Hicksville OH. I would like to be tested there soon. Thanks Nicole! Report
I agree that we all should be able to be tested. I wish if you were overweight (or underweight) that the annual visit to your doctor would prescribe or conduct it right there in their office.
Once a person knew I wish there was an option under SP Food tracker that would up calorie range on moderate/intense workout days or at the very least lower calorie intake range on resting days. Most people know how to schedule their workouts. It would help a lot of people. Report
I'm definitely going to give this a try since I've been unable to break my long-term plateau which has been over 9 months. This blog was excellent! Report
Years ago I did something similar to this, and I would love to try it again now. Report
I need to find a place by me that can do this. I sound like Jaime. I work out 5-7 days and track my food, but nothing is happening. Report
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