Omron Body Fat % Analyzer - How Accurate Is It?

I bought one of these nifty gizmos a few months out from my surgery (wish I had it at the time OF my surgery, as I'm curious what my % was then!)

  If you're not familiar with this device, it is a small, portable electronic machine that has a pair of metal handgrips on the bottom of it.  Using the keypad on the front, you enter your height, weight, gender, age, etc. and then push the "zap" button and grab the handles.  After 7 seconds or so, it sends a small battery current through one handle up your arm and down the other arm to the other handle.  You don't feel it, though.   The LCD display on the front then reads out your BMI and your body fat % ..  It seems the last few months my % is always around 30% ..  This seems high to me, and is almost twice that of some WLS patients I know that weigh only about 50 lbs. less than me .. 

  Does anyone else have one of these units?   do you know how accurate it is (i.e. have you ever compared the readings to that taken by another, similar device or manual fat % calipers)?   I'm wondering also, for us post-ops, how accurate the machine is in light of our loose skin, i.e. does it read the loose skin as "fat" or does it read it as lean body mass?   I suspect the lymphedema in my feet and ankles may also affect the validity of the results, but don't know for sure ..

Hello Paul, I have just written the following for OH Magazine so for the first part I am going to just cut and paste about the accuracy of BIA... Scales measuring or estimating body fat percentage use a process called Bioelectrical Impedance or BIA. BIA is a safe, quick and fairly accurate estimate of body fat percentage, but it must be performed under consistent conditions. Consistency in an individual’s level of hydration and blood circulation is needed for accurate assessment. As you would imagine, hydration and blood circulation fluctuate throughout the day depending on how much you have had to eat and drink, when you last exercised, temperature and other factors. While there are several times during the day that can be used for measurement, the one I most often suggest is first thing in the morning after waking up, as it is generally the most convenient time of the day. Pick a time and stick with it. Consistency is key. When measuring body fat percentage with BIA first thing in the morning, use the following guidelines: • Do so prior to eating, drinking, bathing and/or performing any physical activity. • Do not wear any clothing. • Urinate prior to measuring. Additionally, be sure to read the manual accompanying the scale you use. Many BIA scales have different functions and may use different placement of electrodes; the most common placement for home use BIA scales is four electrodes positioned on the platform of the scale which you stand on. ----------------------- OK now, you brought up a couple of extremely important points. 1. BIA scales use different algorithms to estimate body fat percentage based upon what population or category you fall under. If you are an athlete, male or female, obese, resistance trained, aerobically trained, and several other possible categories, there are different equations for each of these populations. There has not been an algorithm created for individuals who have a large amount of extra skin. So, BIA scales may be somewhat inaccurate for this population. Since there has been no research done to assess the accuracy of BIA for this population it would be difficult to say whether it would be classified as fat or lean mass. This is actually an issue I have been interested in looking at. I would love to do a study that compares the accuracy of BIA to body composition measures such as BodPod and DEXA in individuals with a large amount of extra skin. 2. BIA or bioelectrical impedance estimates body density and body fat based upon the resistance your body provides to electrical current. Fat tissue has less water than muscle tissue so muscle tissue will conduct electrical currents more rapidly than fat. Your level of hydration does play a huge role in this. Additionally, if you do have a condition such as Lymphedema this can cause further inaccuracies. You are using a hand held unit so this somewhat helps this issue but you still maintain weight in that area it is not considering or working into the equation. As a side note, bioelectrical impedance or BIA has more than one use and has actually been used to detect and assess lymphedema. Hope this helps and let me know if you need any other info.

bioelectrical impedance or BIA has more than one use and has actually been used to detect and assess lymphedema.
   wow- very impressive you knew that!       yes, BEI devices currently are is being used to assess upper body lymphedema (e.g. arms) but yet have not been approved for lower body (e.g. legs) LE, TMK  ...   We lower body LEers are eagerly awaiting development of  a lower body LE assessment device ..    a few follow up questions, if you can help ..   #1  how accurate are the weight scale type body fat % analyzers vs. hand-held units like the Omron?    I have been tempted to buy a weight scale type unit, just to compare it to the readings on the Omron unit, but really don't want to plunk down money for it.  Have you (or anyone you know of) ever compared the units that way?    #2  the Omron (and probably the weight scale type analyzers) require that the legs be kept apart when the unit is discharging ... however, many MO and esp. SO patients will have a problem keeping their thighs from contacting each other during the discharge ..  would this situation affect the accuracy of the reading?    #3  the only downside to the Omron that I've found is that, unlike most of the scale-type body fat % analyzers, it does not also calculate hydration levels.  Is there any formula that I can use to calculate my hydration level manually based upon the body fat % readings (and BMI) from the unit?        

Paul, Whether you choose a hand held or standing BIA device, they will both be very similar. If nothing else, when performed under standard conditions it will give an idea of where you body fat percentage is heading....in other words, BIA while relatively accurate, you can certainly use it to simply gauge whether your BF% is increasing or decreasing. There are also units that combine both methods...but again they are all probably pretty similar. I guess you should keep your legs apart as much as possible but this most likely will not skew the results a significant amount either way. Unfortunately there is not really a way to determine total body water from your body fat % alone.....well i guess is would be possible if you were able to get a hold of Omron's algorithm they use to predict BF%. Quite frankly the a good way to see if you are hydrated sufficiently is to simply look at the color of your urine. There is no need to really know the numbers. You can also use Urinary Specific Gravity which is relatively inexpensive. Let me know if you have any other questions.