Featured Great Gadgets — 08 January 2013

By: Jodie Shield, RD

Many of you have asked me what I think about body fat scales – are they accurate?  What’s the best one to buy?  Do they really measure body fat?  Well I confess: my favorite scale – if there is such a thing- is the doctor’s office upright scale.  You simply step on, slide the markers until they balance, then read your weight.  However, I realize this type of scale doesn’t tell you your body fat, BMI or any of the other handy measurements many of us want to know so we can analyze our weight and health. So I went undercover to my local Bed, Bath and Beyond store and bought a body fat scale.  Here’s what I discovered . . .

My first dilemma: so many scales to choose from!  Since I use to write for Weight Watchers and love their updated eating plan, I bought one of their body fat scales and decided to give it a try. This particular scale provided five key measurements: weight (in pounds), body fat weight, body fat percentage, body water, and bone mass. In addition, it contained enough memory to allow me to program the scale for up to four users. Check out my review of  the Weight Watcher scale at the bottom of this article.

How do body fat scales Work?  Most of these types of scales use bioelectrical impedance.  That is to say, they send a safe and very low electrical current through the lower half of the body.  Since the electrical current flows more quickly through water and muscle than bone or fat, the scale measures the speed of the current.  Then based on that number, the scale estimates body fat using a multi-step, mathematical formula. One thing you will want to be aware of which was new to me: if you are pregnant or have an electrical implant such as a heart pacemaker or defibrillator these scales are not recommended.

Are body fat scales Accurate? Good question but the answer depends on several things. Body fat scale readings can be thrown off by the following factors.  In addition,the results may not be accurate for kids under the age of 16, or people with an elevated body temperature, diabetes or other health condition.

  • Hydration.  If you’re dehydrated or sweat a lot from exercise or your climate, you will have less body water for the electric current to flow through.  The result: your body fat reading may be higher than it really is.  And the opposite is also true.  If you drink too much fluid, have a full bladder, or if you are a women experiencing water retention from your menstrual cycle, your body fat reading may be lower than it really is. For best results: be aware of  what affects your fluid retention; weigh yourself once a week, on the same day and at the same time of day; wear the same clothes or none at all.
  • Movement. The electric sensors in these scales are sensitive and work best when weighing stationary objects.  Wiggling around or quickly hoping on the scale can interfere with your reading. For best results: always stand on the same area of the scale platform and stand still.
  • Foot calluses. Some studies have found that having thick calluses on your feet may prevent the electric current from flowing accurately. For best results: shave those calluses. (Did anyone say pedicure?)
  • Muscle.  Heavy-duty weight training builds muscle which weighs more then fat.  This can result in a higher body weight measurement which can throw off the arithmetic in the body fat and BMI formulas (To calculate BMI, visit my home page.) For best results: if you do a lot of resistance weight training, these scales may not be your best option.

Great Gadget Review for:

Weight Watchers Conair Body Fat Scale (model #WW78) 

Pros: I was pleasantly surprised how accurate the Weight Watchers body fat scale was for me. My weight was spot on, BMI correct, and my body fat percentage matched the reading I had confirmed by a personal trainer at my local health club. The initial set up took awhile, but after that using the scale was quick and easy. And it was fairly inexpensive $29.99. (The majority of body fat scales ranged between $30-$50 dollars.)

Cons: The five different readings flashed by way too quickly.  And I had no clue what they meant.  The owner’s manual came with some excellent charts which I would recommend you hang nearby or keep handy.

Healthy Eating For Families Recommendation: 4 out of 5 stars






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About Author


Jodie Shield, M.Ed., R.D., L.D.N. Jodie Shield has been a consultant and spokesperson in the field of nutrition for over two decades. A former national media spokesperson for the American Dietetic Association (1989-1995), she has worked extensively with the Rush-Presbyterian-St. Luke’s Medical Center and taught nutrition and medical dietetics at the University of Illinois. Currently she is a complemental faculty member of the College of Health Sciences in the Department of Clinical Nutrition at Rush University in Chicago.

(37) Readers Comments

  1. I have a metal hip implant. Would that effect the accuracy of the scale?

    • Jodie

      Great question! It sure would. This type of scale would not be accurate for you or anybody else with metal implants – knee or hip.

      • Jodie, I’m confident the case will be the same; however, you mentioned knee/hip implants would affect the reading, but not leg rods. I have a titanium IM Rod/Nail from a broken tibia I suffered 13 years ago, and it’ll never be removed. Will this render everything but the weight metric off-kilter and if so are there any scales (w advanced features) that wouldn’t be useless for someone like myself? Kind Regards.

        • Jodie

          Hi Peter. Sorry to hear about your broken tibia! Your assumptions are correct! Good luck.

  2. Great Article Jodi!

    • Jodie

      Thanks Carole! Hope it helped.

  3. Truthfully – we know that we are fat, don’t we? I personally hate any type of scale. Mirrors don’t lie nor do our clothes. I don’t use the scale, I look in the mirror.

  4. I agree on the numbers flashing by quickly. I have the HoMedics name brand BMI scale and need to use my smart phone voice recorder to quickly take note of what my readings are.

    I have also learned that if the scale has all it’s feet on the ground opposed to if there is a foot or more on a bathmat, I will get different readings. Not that they are inconsistent with each weighing, ie, every time I weigh with the a foot on the bath mat, it provides consistent readings. Same goes for when all the feet are touching the floor, but those readings will be a few decimals off from if feet are on the bath mat.

  5. That scale did not get a good review in Amazon. Plus I read from several sources body fat measurements from scales is pretty inaccurate. The writer didn’t look into this enough.

    • Jodie

      Thanks for your comment. Do you have a scale you recommend?

  6. Is it ok to this tipe of scale for babies/small kids just to masure their weight? So you use it just like a regular scale. My scale has that option when you use it like a regular scale and option where it masures body fat/water…

    • Jodie

      Good question! Since a child’s BMI and body fat is not calculated in the same way as adult’s BMI or body fat, this type of scale would not provide accurate readings for those measurements. However, you could use it just for weight if your child is willing to stand still. When my children were young, I use to weight myself first, then weigh myself holding a child and then subtract my weight from the total combined weight to get my child’s weight. Hope this helps!

      • Yes, that how i it too. But our old scale wasnt accurate any more, and hubby bought this one now that massures all this things.
        Thanks for replay!

  7. Hello, I just used a Bioelectric Impedence scale and it said that I have too much fat, too little muscle and that I have the body composition of a 36-year-old. I’m 28, I kickbox, I occasionally lift moderate to heavy weights and I rarely eat junk food. I measured myself right after a hard workout so I’m kind of curious what happened. I’m 5’7″ and way 158lbs. I’m not fat or skinny so I’m not sure what is going on. Is my health in danger?

    Thank you,
    Andrew C.

    • Jodie

      How frustrating for you! Sounds like you are doing a really excellent job of working out and trying to eat healthy. As I mentioned in my blog post, these scales are not for everyone. Hard for me to say for sure what happened. However, if you are concerned about your health, I highly recommend you give your doctor a call.

    • It’s NOT recommended to use them directly after heavy exercise as you may be relatively dehydrated, which I believe would lead to a higher reading for % body fat. Try last thing at night before going to bed.

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  11. I recently purchase a Taylor Personal Scale, it has all of the above mentioned readings with the exception of bone mass. I was curious what the healthy ranges are for a Female for the body water %. Also my scale has an Athlete Mode they consider an athlete someone who exercises 3x a week for at least 2 hours. I currently do a crossfit work out 3-4 times a week which is very intense. When should i start using this function. I am still about 30 overweight, but have lost 30 lbs. I have been doing crossfit for about 2 months, but have taken the last month off because I recently got married and went on honeymoon. Thank you

    • Jodie

      Hi Kelly,
      Good for you for working out and congrats on your weight loss! Good question about the body water. I really don’t put much emphasis on this value because it fluctuates tremendously based on what we eat, hormones, temperature, etc. As for when to consider yourself an athlete, that’s your call. I have found that using a moderate to high activity works best for most people. Having said that, my son plays college football and works out well over two hours a day – intensely. So my default is to leave the Athlete Mode up to the individual.

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