Scales On Balance

Scales On Balance

Are they helpful for weight loss?

By Steve Anthony

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In the weight loss context, the use of a scale is often discouraged because those that frequently weigh themselves end up being discouraged about their progress.

It is important to keep in mind that a scale is a measurement instrument. It seems easy to use, but there are things about scales that many people don’t know — or don’t know how they impact the way you should use one.

In this article we will discuss:

· The reliability and accuracy of scales (focusing on the digital bathroom scale)

· How a digital scale works

· How to set up and test your scale

· How to weigh yourself

Reliability and Accuracy

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First, and foremost, when you are trying to lose weight, you should focus on the way your weight trends over time — over weeks or months. Don’t worry about day-to-day changes. You will see as you read on why looking at day-to-day changes can give you a false sense of what’s going on with your weight and drive you crazy if you try to analyze those day-to-day changes.

Let’s start with a basic, digital, bathroom scale. There is quite a wide range of scales out there with different bells and whistles that will connect to your phone, measure your % body fat mass and/or lean mass, etc. What we all want is a reliable, accurate scale at an affordable price.

Reliability refers to whether the scale gives youthe same result if you put the same weight on it multiple times. So, if you step on it, say, 3 times in a minute you want to get the same weight as a result. If it doesn’t provide you with the same result each time, you will want to know how different the results are from each other. If you spend around $30 on a digital you should be able to get one that is reliable — and will give you identical readings for the same object (with some caveats listed later).

Accuracy is the ability of the scale to tell you how much you really weigh. Again, for your $30 investment, you should be able to get on that is at least accurate to within half a pound. Yes — plus or minus half a pound is considered accurate for a digital bathroom scale. If you want something better, there are “ultra-precise” scales that measure to within 1/100th of a pound that cost in the neighborhood of $3500 (plus shipping).

In the weight loss context, we are generally concerned with the accuracy of detecting the change in our weight. So keep in mind that if your scale is only accurate to within a half a pound, you can lose (or gain) almost half a pound and your scale might not show it. That’s one reason to look at the trend versus day-to-day changes.

You can test the accuracy of your scale in a couple of ways. But before we get into that, let’s look at how a digital scale works because that will give us some tips on how to test and use our scale.

How a Digital Scale Works

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A digital scale works differently than the scales you might see in a doctor’s office. And just to restate the obvious, a bathroom scale is used to measure weight — your weight. Your weight is really the downward force you create due to gravity. No gravity, no weight!

So, the scale is measuring the downward force you create. It does this with a device called a strain gauge, also known as a force transducer. Seeing these two terms for the same device gives a sense of what it does. When you step on it, you exert downward force to the top of the scale. That force creates a strain on the material under the top of the scale by pushing down one side of it while the other stays fixed. Think of a diving board: when you put something on the end over the water, it bends. When it bends, the top of the board stretches under the strain of the downward force, while the bottom compresses. The same thing happens in the force transducer. The force transducer has an electric current going through it and the current changes depending on how much the top is stretched and the bottom is compressed. This change in signal is then transformed (transduced) into a value that a microprocessor shows on the LED or LCD display.

Not bad for $30!

A big note here is that the force on the top of the scale needs to be “collected” from wherever you stand and mechanically transferred to the force transducer. This has some implications when it comes to using the scale — that is, when weighting yourself. And these implications impact the reliability and accuracy of the scale beyond the stated specs of the scale. In other words, while the manufacturer might say the scale is accurate to within half a pound, if you don’t set up and use the scale correctly, your reliability and accuracy will be worse.

How to Set Up and Test Your Scale

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Some scales need an initial calibration. Others don’t — so check the manual for your scale.

When calibrating or when setting it up to use, be sure the scale is on a hard, flat surface. The reason for this is you want the force that you exert on the scale to be evenly distributed on the four feet of the scale — because these feet contain the mechanical linkages to the force transducer. If you put the scale on an uneven surface like a carpet or on even a slight incline, the mechanics of the linkages will be thrown off and you will get an inaccurate reading of your weight. I even tried putting the scale on a board on top of carpeting, and did not get good results.

I tested my scale with a 5 kg free-weight I have at home. Depending on where I put it, it weighs between 4.5 kg and 5 kg. Why did this happen? Think back to the diving board example. If you put a weight at the very end of the diving board, it bends more than if you put the same weight closer to the point where it is fixed to the side of the pool. This brings up another important note: Where you stand on the scale will impact the weight the scale shows you. Interestingly, the apparent “accurate” spot — where the free-weight registered 5 kg — is lightly forward of the center of the scale. So when I weigh myself, I try to stand over this spot. If you aren’t obsessive about the accuracy, and are just looking at the trend, it’s enough to just always stand in about the same spot on the scale. But to the degree you don’t stand on the same spot will impact your day-to-day weight reading. Another reason to watch the trend over time.

In addition to weighing just the free-weight, I also weighed myself, then myself holding the free-weight, to see if at higher weight ranges, the scale “sees” the free-weight as being 5 kg. And it does not — it sees the 5 kg free-weight as 5.4 kg. So, my scale will tell me I’m gaining a bit more weight than I am, when I gain, and losing a bit less than I am, when I lose. Still not bad for $30.

How to Weigh Yourself

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Treat the measurement of your weight as a science experiment. If you are on some kind of weight loss plan, the experiment is to see if the plan is working — is it resulting in your weight going down?

To test the effect of your weight loss plan, you need to measure your weight in a very consistent way and to eliminate as many extraneous factors as you can. So be sure to set up your scale appropriately. And recalibrate or re-test the scale even if you move it a little on the floor. Your scale is actually quite sensitive, so moving it an inch can make a difference

The naked truth is, if you don’t weigh yourself naked, you are not just weighing you. If you weigh yourself wearing the same clothes every time, at least the changes in weight you see will be the changes in your weight. If you are wearing different clothes from measurement to measurement, any weight change you see could be due to your clothing.

Weighing yourself at a consistent time in the morning is a good idea because it’s unlikely you will have eaten anything yet — so you won’t be weighing you + your food. If you weigh yourself in the morning, do so at a consistent point in your “morning routine;” A good pee can weigh as much three-quarters of a pound! If you typically drink a glass of water when you get up, weigh yourself before drinking, every time. The water in an 8 oz glass weighs half a pound! And if you don’t drink the same amount each morning, it will be reflected in your weight read-out. Being consistent will help ensure the changes in weight you see on the scale are only the changes in your weight.

If you are serious about tracking your weight, I recommend recording it in your phone. If you have an app that will show you a graph of your day-to-day weight, so much the better. What you will notice is a jagged line that, hopefully, has an overall downward trend. What you will not likely see is a smooth line heading south. Why? Because your body is not a machine. You act, it reacts. But it reacts on its own time. Some days you will lose weight. Other days your body is going to do more rearranging than using fat for fuel. Your body has its process. Work with it. If you fight it, it will fight back!


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What you will come to learn from your data is not to sweat it if you are “good” for a couple of days but don’t see any weight loss. Metabolism is incredibly complex and involves more than just the food you eat (and it ignores much of the exercise you do!).

Personally, I have found the scale to be a very useful instrument in my weight loss journey. I’m almost at my target weight. But even after I reach it, I will monitor my weight — maybe weekly instead of daily (but I’ll do it on the same day of the week) — to see my reaction as I bring various foods back into my meals (now I do very low-carb, but will increase them a bit once I hit my target).

I hope my article has given you some insights you can use with your bathroom scale. Good luck with your weight management journey!