Tanita Body Fat Percentage Scale

The first in a series of posts on tools and rules I have used for losing weight.

My 8 Year Old Tanita TBF-621

My 8 Year Old Tanita TBF-621

The numbers don’t lie. If you say you want to lose some weight—by which I mean lose some fat, not muscle—then you must be able to quantify the changes to your body. I can almost imagine Coach Glassman saying, if you can’t show that you’re making progress, then what you’re doing isn’t working.

But the thing we have to understand about “weight loss” is that it doesn’t really matter how much you weigh. It’s about the fat on your body. You don’t want to lose weight, you want to lose fat. In fact, unless your weight loss is a loss of excess body fat, then it probably isn’t healthy for you. Enter the Body Fat Scale. I definitely use one. As far as brands go? I really can’t say I’ve tried a variety of brands. In fact, I am familiar only with two models of one brand: Tanita. They’re pretty good. I’ve had mine since April 2001, and only changed the batteries a few times. These scales work by taking a measurement of the electrical impedance of your body. That number, adjusted for age and weight and gender and height and activity level, correlates with the amount of body fat supposedly on your body.

People will sometimes tell you that these body fat scales are not very accurate. In a way that’s true, but not really. What they are is consistent, and their consistency is about as useful as any accuracy. To use them, what is needed is experience and a consistent method of measurement. Then they can be used to track your progress way better than any normal scale.

How to Use a Body Fat Scale

The first thing to realize is that the numbers you get from this scale vary a LOT during the day. Depending on how hydrated you are, depending upon how active you have been for several hours before weighing in, or how long it has been since you slept, depending on the content of your stomach and bowels and bladder, depending on your body temperature or the moisture content of your skin, you may get different readings. So the question becomes, how do you use this thing?



  1. Keep track of your numbers on a spreadsheet or chart.
  2. Keep track of the date and time of each reading of weight and body fat, and use an additional column for notes.
  3. Over the course of one week, weigh yourself a few times. Do this at a variety of times: whenever you can manage to get naked in your bathroom. Get at least four sets of readings during the week, all taken at different points in the day.
  4. In your spreadsheet, once a week you should record the range you observed during the week: your highest and lowest recorded weight, and your highest and lowest recorded body fat percentage.
  5. Week to week, don’t expect to see big swings. Just look for a gradual reduction of both ends of the ranges you measure. It’s all about the trend and the averages.

Remember: these scales don’t provide a very precise measurement. For example, mine gives readings only in whole percentage numbers. That means I have to lose more than 1.8 pounds of fat to lose a percentage point on the scale. But over time, the highest weight I record in any given week has always decreased along the same “curve” as the lowest weight I record during the week. The lowest body fat percentage I observe (often this can be measured at the very end of an active day, several hours after last eating) always decreases at the same rate or along the same “curve” as the highest body fat percentage I observe.

An example of my weight chart

Date Weight BF % Fat Observed Range of Weight over the week Observed Range of BF % over the week
3/29/2009 198.5 18% 35.73 195.0—203 18—21
4/5/2009 195.0 17% 33.15 194.2—199.5 17—21
4/12/2009 194.0 16% 31.04 193.5—198.5 15—20
4/19/2009 192.5 16% 30.8 191.0—196.0 15—20
4/26/2009 191.0 16% 30.56 189.4—193 16—19
5/3/2009 191.5 15% 28.7 187.0—193 15—18

As you can see from this table, there are times when your weight might seem to be increasing, or when you might not seem to be making progress, but the trend in the ranges you observe is what shows the real progress.


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Filed under Nutrition, Weight Loss Arsenal

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