Adventures in Metabolic Testing
At ADA-FNCE last week, I had my metabolic rate measured at the Korr Medical Technologies booth. (I have no connection with them.) I’ve always wanted to see my metabolism numbers and so I loved getting the report, but as you can see, the experience was an encounter of the dental kind. Was the report worth the bother? How did the results compare with the standard calculations?
The machine you see measures metabolic rate. The account rep said the machine is in doctors’ offices (but not in my doctor's office). The process is called "Indirect Calorimetry." It calculates your calorie burn rate by measuring your oxygen uptake, which is a standard procedure that has been around for many years.
“Metabolism” refers to the rate at which you burn calories. Calories at rest for physiologic functions is your BMR (Basal Metabolic Rate), sometimes called REE (Resting Energy Expenditure) or RMR (Resting Metabolic Rate). The test also estimates the calories you burn performing ADLs (Activities of Daily Living), such as dressing and eating, and on PA (Physical Activity) like exercise or labor. Add up the three numbers to find your calorie requirements. In addition, the metabolic test compares your BMR to a "predictive normal” to tell if you burn fast, slow or in-between (which is normal).
The procedure entailed resting and reclining while breathing into a mouthpiece. My nose was clipped shut to force all air to pass directly into the chamber hooked to the machine. (The guy who set me up neglected to tell me that I could remove the mouthpiece to swallow, and swallowing saliva was quite tricky. Rrrrr…) The test was completed in 10-12 minutes and the calculations were displayed on the screen and printed in a report.
First, let me say that I am particularly petite and getting on in years - so don't expect me to need many calories. And then, I think I reported my height and weight correctly, but I can’t be sure. And the testers knew I wasn’t completely fasted, but neither was I stuffed.
By machine, my calories burned were:
BMR: 1282 + ADL: 384 + PA: 133 = 1799 calories a day to maintain my weight.
- Compared to normal, my metabolism is faster.
- Activity = 30 minutes of walking at 3.5 miles per hour
By standard calculations, my calories burned were:
BMR: 952 + ADL: 286 + PA: 90 = 1328 calories a day to maintain my weight.
Wow! Big difference - 471 calories or 26% - between the total calories burned as calculated by the machine and by the formula. Compared to "normal", the machine showed I burn more calories at rest, with exercise, and in day-to-day living. I guess my faster-than-normal metabolism made the difference. Perhaps it's because I have more muscle than some women my age and because my weight did not fluctuate throughout life. And then there's my genes - or the test could be wrong.
To tell you the truth, I don’t trust the machine's results, not because it's inaccurate (because I think it is), but because I wasn’t tested correctly at the convention. If I ever take the test again, I will take the average of three measurements to determine my height and weight and comply with the manufacturer's recommendations to fast for 12 hours, abstain from exercise for 48 hours and be tested in a quiet room. And then, I'll do the metabolic test two or three times and take the average before I believe the results.
Calorie Count uses the Mifflin-St. Jeor formula to estimate BRM. The formula is accurate by within 8.7% ± 6.0% and it is one of the most accurate formulas; however, The Journal of the American Dietetic Association reported, “…most prediction equations inaccurately estimate BMR in midlife women. More research is needed to validate prediction equations for women across the adult lifespan.”
And so, as I've said before, calorie counting is inexact, but it’s the best we have. Calorie Count will keep up with the latest nutrition news for you. Your job is to pay close attention to what you eat.
Have you had your metabolism tested? What did you see?