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Guest RD: Metabolic Testing

Today’s guest post is by Katherine Horner, MS, RD, LD, NASM-CPT, CES. (Whoa that’s a lot of credentials!) Katherine is here to tell us about her experience going through metabolic testing as well as some background on how dietitians work with these numbers. I actually had the opportunity take a similar test many years ago. I think this stuff is so cool!

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At least one point in all of our lives we’ve plugged our height and weight into an online calculator in hopes of discovering the amount of calories we should be eating to make all our weight loss dreams come true. However, many of us have wondered how this number get’s calculated and why that magical number works for weight loss. To let the cat out of the bag, that number is all based off of something called Resting Metabolic Rate. So throw on your lab coat and let’s get scientific.

Resting Metabolic Rate (RMR) is the number of calories the body burns in 24 hours at a resting state. This would be the total calories the body used if you were to sleep or lay down all day. This amount is usually estimated using predictive equations like Mifflin St. Jeor and Harris Benedict. Equations are obviously the easiest way to calculate RMR, but they are also the least accurate method. The more exact way to measure RMR is through a breath test.

My interest in an RMR breath test came from knowing that predictive equations weren’t the end all be all to RMR calculations. As a dietitian, I wanted to experience the breath test for myself so I could better assist my patients.

I was able to get a breath test at a local gym in my area. Breath tests are usually offered at healthcare and fitness facilities. While they are more expensive than the null expense of predictive equations, they are often very reasonable. The test works by measuring the amount of air you exhale and thus determining the amount of oxygen your body is consuming. This can then be calculated to discover how many calories you are burning based off an “oxygen consumed per calorie burn” ratio.

Prior to RMR testing most clients work with a dietitian on specific diet and health goals. Since I’m a dietitian myself I did not go over any goals with my test facilitator, who happened to be another dietitian, ahead of time (you’ll see this section blank on my results page).

My breath test was scheduled for 8am and I was instructed not to eat or drink after midnight the previous night. This is to ensure that the body isn’t digesting food, which would burn additional calories and impact results of the test (if I was digesting food during the test then my body wouldn’t be at total rest!). Some tests require fasting while others do not.

On the day of my test I was ushered into a quiet room and took a seat in a very comfortable reclining chair. The dietitian worked to set up the equipment and gave me instructions for the test. I was educated to breath in and out of my mouth at a normal rate during the testing period. A nose plug was used to make sure that I was breathing solely through my mouth. The dietitian handed me a long, clear plastic tube that was attached to a machine she had previously set up. I would be using my mouth breathing to breathe directly into the tube during the test. She also gave me a towel as drooling can be a side effect of mouth breathing! I practiced and got used to the breathing apparatus before she started the machine. I also had to get over my giggles as my breathing sounded like Darth Vadar. I quickly adjusted to the tube and mouth breathing and was able to relax.

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About fifteen minutes into my test the dietitian came back and checked the machine. She let me know the test was completed and a few minutes later my results were printed.

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The gym I went to uses the MetaCheck Analysis System, which provides you with a very thorough explanation and handout of your results. My RMR test showed that I burn around 2261 calories per day at rest. The test also estimates the amount of calories you burn from exercise and activity throughout the day. This amount is added to your RMR to give you the total number of calories you burn in a day.

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On the right side of the results page, the machine calculated how many calories I would need to consume for weight maintenance and weight loss.

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Finally the results explain the speed of your metabolism and what that means. Along with that, the machine calculates how long it will take you to reach your goal weight through diet and exercise.

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This information is very useful as I find that many times I am not eating enough for my body. After having this experience I try to continually remind my patients that our bodies work hard throughout the day and we need to fuel them properly. Even for desired weight loss we have to provide a significant amount of calories to our ever-burning body.

I highly recommend having the experience of an RMR breath test for clients wanting to be more in control of their weight maintenance and weight loss lifestyle. Also, remember that RMR can change based on weight, body composition and exercise routine. The results of your RMR test are not forever and should be completed again if you have any significant lifestyle changes.

References

http://metatestvo2.com/metabolic_testing.shtml

Katie

Katherine (Katie) Horner is a Registered Dietitian with her Masters in Exercise Science. She works as a surgical weight loss dietitian in Greenville, SC, as well as a sports nutrition counselor at a local health club and university. Katie is also a NASM Certified Personal Trainer and Corrective Exercise Specialist. Katie has recently opened KP3 Nutrition and Fitness LLC to counsel individuals in her local area as well as those via Skype or online. She loves to help her clients work towards a healthier lifestyle with a balanced diet and exercise routine. Her blog, at kphornerrd.weebly.com, has workouts, recipes, advice and information to help you achieve your health goals.

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Reader Interactions

Comments

  3. I did this test several years ago and felt like I could never regulate my breathing to normal so I don’t know if I trust the results I got on that one. I wish they’d given me the opportunity to normalize my breathing longer than like 30 seconds. Thanks for reminding me I still have another free one coming to me!

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  4. This is fascinating! Even with her fast metabolism, it sure blows the “1200 calories a day for weight loss” theory out of the water. It makes me wonder how seriously undernourished we are in an effort to restrict calories and lose weight. Its so great to see fit women eating real food and not subsisting on lettuce and grilled chicken breast all the time.

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  5. I think metabolic testing is amazing! I still have a BodyGem metabolic machine left over from when I was a health coach and now I’m itching to pull it out and test my metabolism again just to see how it’s changed! The info really helped me a couple of years ago when to make sure I was eating enough while breastfeeding. Great post!

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  7. Wow, this is so eye-opening! I agree with Shana’s above comment – the 1,200 calorie a day goal for weight loss seems even more ridiculous after reading this. I want to get my RMR tested too 🙂

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  8. I LOVE the RD posts! More more more!!!!!!!! 😀
    Any other advice on when to do/not do this test? I’m looking into getting it done. So not when you’ve recently eaten a HUGE meal or exercised…. Does anything else throw off the results? What about “that time of the month?” 🙂

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    • Some studies do show that the menstrual cycle can throw off your RMR due to hormones. It may be best to perform the test at an alternate time during the month. However, I was not told to avoid certain times of the month when I went in for my testing.

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  11. Wow – so much great information that I never knew about. I need to look into something like that in my area. It would be really helpful to get the number breakdown on calories to eat for the different zones. I have a scale that is supposed to measure some of that stuff but I doubt it’s as accurate!

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  13. So I was reading this and as I made my way to the bottom and saw Katie’s picture and I realized I knew her!!! Hi Katie! This is Amanda from softball! So glad to have found your blog lol.

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    • I would say one of the best ways to speed up metabolism and increase your RMR is through exercise. The more lean body mass one has the more calories the body burns. One of the many benefits of strength training!

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  15. I did that last year too. I can’t remember my results (I don’t really stress over calories in and calories out) but considering I eat over 3000 calories a day, do HIIT workouts, and still maintain a healthy, fit, lean body I am sure I am doing just fine.

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    • If you google RMR testing and your location a couple things should pop up. You can also call healthclubs or hospitals and they should have an idea of where you can get it done!

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  19. I’m wondering whether you have found that chronic dieters tend to have lower RMR (another reason to not eat too few calories)

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    • Yes! Chronic dieters as well as restrictive eaters do tend to have lower RMRs. However, it is not something that can’t be improved through proper caloric consumption and exercise!

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  20. Wow! Like some of the other readers, I am surprised by the 3000 calories/ fast metabolism, and I am curious to know what mine is! Is it possible to increase your standing metabolism by things like diet and exercise, or is it pretty much set by genetics?

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    • Genetics does play a role in your metabolism and eating patterns. However, you can absolutely improve your metabolism through diet and exercise. Just another reason to eat well and hit the gym!

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    • My test looked like yours Lyn when I had it done years ago. I wonder if mine is the same now that I’m older and (hopefully) have more muscle.

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    • Very interesting Lyn! So for some people, 1200 calories really is what they need to eat for weight loss! I would love to have this test done!

      Would love to see more stuff like this Kath. Great post Katie!

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  22. That looks really interesting! Does anyone know how much something like that usually costs? It would be really interesting to see what it is now, and then test again in six months after making some changes 🙂

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    • Funny enough we are actually looking into getting one of those where I work. I have used them before and they do a decent job, but it is still only an estimate. The breath test can increase accuracy, but the scale is fairly reliable, less expensive and more easy to perform so most practices are opting for it.

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  25. ACAC in Cville does it.
    Metabolism Assessment In this one-hour session, your resting metabolic rate is measured using the MedGem™ tool, an indirect calorimeter (breathing device). The score is interpreted and presented in calories. The remainder of the appointment is a discussion about metabolism, energy, and stamina in relation to exercise. Member: $89, Non-member: $99 – See more at: http://www.acac.com/2013/03/21/nutrition-menu-of-services/#sthash.IHnZYfyt.dpuf

    Reply

  26. I know this was awhile back but I’m curious, did you find that you burned way more than you had previously thought?

    Reply

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