You step on it in the morning, the screen flashes for a couple of seconds, and suddenly it gives you a series of numbers. Weight, BMI, body fat, water, muscle, bone, basal metabolic rate, and something called metabolic age that tells you you’re 44 when you’re 38. You stare at the app for a while. And in the end, you do what we all do. You look at your weight, compare it with yesterday’s, and the other seven numbers are left abandoned because you’re not quite sure what to do with them.
It happens to almost everyone. And it’s not your fault; no one has explained what those indicators on your scale actually mean.
A bioimpedance scale doesn’t see your fat. It doesn’t see your muscle either. What it does is send an electrical current so gentle that you don’t even notice it and measure how difficult it is for that current to pass through your body. Using that information, along with your weight, height, age, and sex, a formula calculates everything else. In other words, the only number on that entire screen that is actually measured is your weight. The rest are estimates. Good and useful ones, but estimates nonetheless.
And far from being bad news, understanding this is precisely what turns your bioimpedance scale into a very useful tool for everyday life.
| What you see on the screen | What it really is | How you should use it |
|---|---|---|
| Weight | Direct measurement, the only one on the entire screen | Trust the number, but look at the weekly average |
| BMI | A division of your weight by your height, nothing more | A quick reference; it doesn’t tell you whether it’s muscle or fat |
| Body fat | Estimated from electrical resistance | Track the trend on your scale and forget the exact number |
| Muscle mass | An estimate, with different ranges for each brand | Your own history is the reference, not a number from the internet |
| Body water | An estimate, and the number that fluctuates the most from one day to the next | Compare weeks, never two isolated days |
| Basal metabolic rate | Calculated from another estimate | Useful for tracking the trend, not as an exact figure |
Are you weighing yourself correctly?
Tell us when and how often you weigh yourself, and we’ll tell you whether your reading is useful for comparison or is just confusing you.
What your scale does when you step on it
Bioimpedance sounds like something from a laboratory, but it’s actually quite simple to understand how it works. The scale sends a very weak alternating electrical current through your body. You don’t feel it, it doesn’t hurt, and nothing happens. The only thing it really measures is how much resistance that current encounters as it passes through you.
So what does electricity have to do with your fat? Well, it turns out your tissues don’t all conduct electricity the same way. Water and electrolytes conduct electricity brilliantly. Fat and bone, terribly. And muscle, which contains considerably more water than fat, conducts it much better.
That’s the whole mechanism. If the current has difficulty passing through you, the algorithm assumes there’s more fat and less lean mass. If it passes easily, the opposite. It then applies a formula, different for each brand, and translates all that into liters of water, kilos of fat, and kilos of muscle.
Not all smart scales measure the same way
Here’s a technical difference almost nobody tells you about when you buy one, and it explains why two smart scales that look similar can give you quite different readings.
Home scales usually send a single electrical frequency. They’re simple, inexpensive, and perfectly adequate for tracking a trend over the weeks. The multifrequency devices you see in a dietitian’s office or at a gym send several different frequencies. This allows them to distinguish the water inside your cells from the water outside them, making their estimates more precise.
But pay attention to this, because it’s important. Neither one can see your fat. Both calculate it. The multifrequency model starts with more information, and that’s it. It’s still an estimate made using a formula.
And there’s a second factor that’s also decisive: the path the current takes. Think about it for a moment. If the scale only has electrodes on the platform, the current enters through one foot, travels up, comes down, and exits through the other. It has traveled through your legs. Everything else, your torso and arms, is estimated from that.
By contrast, if the scale has handles or a bar that you hold with your hands, like the Wellbeinn Balance, the current completes the circuit. Feet, torso, arms. It’s a real difference in data quality, not a gimmick.
How to weigh yourself so the number means something
This is the part most people skip, and the one that most determines whether your scale is useful or just drives you crazy. Because bioimpedance is sensitive to almost everything you did in the last 24 hours.
Did you have an overly salty dinner last night? It counts. Did you work out yesterday afternoon? It counts. Those two beers on Friday? They count. That’s why a measurement taken under any conditions is not comparable with another taken under any conditions.
| Condition | What to do |
|---|---|
| Time of day | Always the same. Ideally, in the morning just after getting up and after going to the bathroom |
| Fasting | A normal breakfast barely affects the reading, according to recent studies. A heavy meal or a lot of liquid in the preceding hour does |
| Exercise | Don't do a hard workout right beforehand if you're going to compare readings. Intense exercise changes tissue hydration |
| Alcohol | Avoid it for 24 hours beforehand. It dehydrates you and throws off the body water reading |
| Metal and footwear | Barefoot or wearing thin socks, with no rings or bracelets touching the electrodes |
| Clothing | More or less the same each time. It doesn't change much, but it helps with consistency |
| Menstrual cycle | Water and weight normally increase in the days before your period. Don't compare those days with the rest of the month |
| Same device | Each brand has its own formula. Comparing the number between two different scales is meaningless |
Here's something reassuring. When these conditions are strictly controlled, as in laboratory studies, bioimpedance devices are fairly stable and produce consistent results between measurements. At home, without that control, the margin of variation is greater. But here's the important point: it's not that the device is failing. It's that your body really does change from one day to the next. Those extra two kilos on Monday after a family meal aren't fat. It's probably water, and it will go away on its own in two days.
Now, what each number means
Let's go through the eight figures that a bioimpedance scale usually displays. I'll explain them in order of actual usefulness, not in the order they appear on the screen.
Weight and BMI, the classic that misleads
Weight is the only honest figure on the entire screen, the only one that is measured rather than calculated. BMI is a division that comes afterward: your weight in kilos divided by your height in metres squared. That's it.
| BMI | Category according to the WHO |
|---|---|
| Less than 18.5 | Underweight |
| 18.5 to 24.9 | Normal |
| 25 to 29.9 | Overweight |
| 30 or more | Obesity |
And here comes the problem with BMI. It has no idea where your weight comes from. A guy who lifts weights four days a week, with 95 kilos of muscle and little fat, is classified as "overweight" in this table. And a sedentary older person, with little muscle and quite a lot of fat, may be classified as "normal" while having a considerably higher metabolic risk.
That is why BMI is used for public health statistics and population studies, which is what it was invented for. As an individual tool, it falls far short. In fact, if your scale shows body fat and muscle, those two numbers tell you much more than BMI.
Body fat, the one we all look at
It is the percentage of your weight that consists of fatty tissue. Unlike BMI, this one does distinguish where your kilos come from.
| Category | Women | Men |
|---|---|---|
| Essential fat | 10 to 13% | 2 to 5% |
| Athletic | 14 to 20% | 6 to 13% |
| Good physical fitness | 21 to 24% | 14 to 17% |
| Acceptable | 25 to 31% | 18 to 24% |
| Obesity | 32% or more | 25% or more |
These categories come from the American Council on Exercise. And one thing worth knowing is that healthy ranges widen slightly with age, especially after 40 and 50. The body of a 28-year-old woman is not the same as that of a 52-year-old woman, and the ranges take that into account.
As for how much you can trust the exact number, compared with DEXA, which is the true reference method, the margin of error can be several percentage points and varies from one brand to another. It works very well for seeing whether your percentage is rising or falling on your own scale. It doesn’t work for comparing it with the number your doctor gave you, your sister-in-law’s number or the number from the gym scale.
Visceral fat, the one that really matters
This is the fat that surrounds your organs inside your body, around the liver, pancreas and intestines. It has nothing to do with subcutaneous fat, which is the fat you can see and pinch. Visceral fat is much more metabolically active and is considerably more closely linked to cardiovascular and metabolic risk.
| Level on a scale from 1 to 59 | Interpretation |
|---|---|
| 1 to 9 | Healthy range |
| 10 to 14 | High, it’s worth reviewing your habits |
| 15 or more | Very high, discuss it with your doctor |
One thing to watch out for: this scale is not universal. Each manufacturer creates its own range, so the number may vary between devices. The only way to measure visceral fat with real accuracy is a CT scan or an MRI, and neither is practical or makes sense to do every month. So take it for what it is: an estimate.
Muscle mass, the one you should pay more attention to
Skeletal muscle mass is the muscle you move yourself: your arms, legs and torso. Fat-free mass is a broader category: everything that isn’t fat, meaning muscle plus water plus bones plus organs. Your scale will show you one of the two, or both.
And here’s why I think this number is the most underrated one on the entire screen. Muscle is the most metabolically active tissue you can change through your habits. It is primarily responsible for your metabolism rising or falling over the years. And it is what will give you strength and independence when you’re 70. Losing it, whether through a sedentary lifestyle or eating too little protein, is what lowers your resting energy expenditure the most in the long term.
Body water, one of the things we’re all most concerned about
It is the percentage of your body weight that is water, inside and outside your cells. And, without question, it is the number that fluctuates the most from one day to the next. It depends on what you had for dinner, whether you worked out, how hot it was, how much alcohol you drank and, if you’re a woman, where you are in your cycle.
| Sex | Typical healthy range |
|---|---|
| Women | 45 to 60 % |
| Men | 50 to 65 % |
Men are slightly higher because, on average, they have more muscle, and muscle retains more water than fat.
Now, a point that confuses a great many people. Having a high water percentage does not mean that you're retaining fluid. It sounds contradictory, but it isn't. A well-hydrated body with good muscle mass naturally contains quite a lot of water. The feeling of bloating has more to do with how that water is distributed between inside and outside the cells - something sodium influences quite a bit - than with the total amount you have.
Bone mass, metabolic age, and the rest
Bone mass is an estimate of how much your skeleton weighs, which is usually between 3 % and 5 % of your body weight. It has nothing to do with a bone densitometry scan, which actually measures bone mineral density. This is just a rough estimate, nothing more.
And then there's metabolic age, which is the most annoying one when it comes out high. It compares your basal metabolic rate with the average for other ages. It's a motivational tool, not a clinical marker. There is no real age you can have inside. It's fine for getting you hooked on measuring and seeing whether your trend improves, but don't organize your life around that number.
Basal metabolic rate
It's the energy you expend while lying down without doing absolutely anything. Breathing, pumping blood, repairing cells, maintaining your temperature, and keeping your brain working. And pay attention to this figure, because for most people it accounts for between 60 % and 75 % of everything they expend in a day. In other words, most of your energy expenditure happens without you doing anything.
What does it depend on? Above all, your muscle mass, which is the factor you can actually change, because muscle burns more at rest than fat. It also depends on age, which lowers it over the years, largely because people tend to lose muscle. Sex matters too. And genetics and hormones, with the thyroid able to shift it quite a bit.
No scale measures this directly, just to be clear. It calculates it using a formula based on your estimated body composition. Measuring it properly requires indirect calorimetry - breathing into a device - and you don't have that in your home bathroom.
When you shouldn't rely on it, or should avoid using it altogether
This part isn't fine print at the end; it's genuinely important, and I prefer to put it before talking about the product.
There are situations in which you should consult a professional before using it, or at least disable fat measurement.
- Pacemaker or implantable defibrillator. The scale passes an electrical current through your body. Several studies have found no problems with cardiac devices, but it remains contraindicated as a precaution. Don’t step on it unless your cardiologist says it’s okay.
- Pregnancy. Stepping on the scale poses no known risk, but the body-fat reading has not been validated for this stage, so it won’t be useful to you. If possible, disable that metric and stick to weight.
- Children. The formulas are based on adult populations and are not reliable for children.
- Metal implants or pins in your legs. They can affect the reading. Talk to your doctor if you have any doubts.
- If you have had an eating disorder. Daily measurements and chasing numbers can reinforce patterns that aren’t good for you. Talk this over with a professional before adding a scale to your routine, without exception.
And there are times when the number will be distorted even though you’re perfectly healthy. Immediately after intense exercise, a sauna, or a hot bath. Immediately after a heavy meal or drinking. If you have a fever, are dehydrated, or have swelling that is already being investigated by a doctor.
So, can I trust it or not?
The reference standard for body composition is DEXA, or densitometry. Compared with it, properly standardized bioelectrical impedance provides reasonable estimates of total body water and moderate accuracy for fat and fat-free mass. At home, without laboratory controls, the margin of error compared with the true value is greater.
Does that make your scale a useless gadget? Not at all. It means it serves the purpose it’s designed for, which is quite a lot. What really provides value is the trend on your own scale, not the absolute number on some random Tuesday.
And here’s the practical part. Getting a DEXA scan every week isn’t realistic, either in terms of cost or time. Stepping on your scale every morning, under the same conditions, is. In the end, the tool you use every week gives you more cumulative information than the perfect tool you use once a year.
Wellbeinn Balance, and why it has a handle
I was telling you earlier that two things determine the quality of the estimate: frequency and the path the current takes. Well, the latter is exactly why the Wellbeinn Balance has a handle.
Most smart home scales measure from foot to foot. The current enters through one foot, travels up the legs, and exits through the other. The torso and arms are estimated from that. It works, but you’re building one estimate on top of another.
Balance has a retractable handle that rises from the platform itself. When you hold it with both hands, the current travels through your entire body - feet, torso, and arms. And that’s the real reason the handle exists; it’s not there to look nice or to hold onto while you weigh yourself. It’s there so the reading is built using information from your entire body, not just the lower half.
The whole process takes three steps and is done in less than a minute.
| Step | What you do |
|---|---|
| 1 · Step onto Balance | Place it on a firm, level floor and step on barefoot, following the usage instructions |
| 2 · Hold the handle | Lift the retractable handle and place your hands on its contact surfaces |
| 3 · Check your measurement | Stay in position during the weigh-in and check your data in Wellbeinn Mate |
It gives you the eight metrics we’ve been breaking down throughout the article. Weight, BMI, body fat, muscle mass, body water, bone mass, basal metabolism, and metabolic age. When you’re finished, the handle folds back onto the scale and disappears, so you don’t have a cable or loose handle lying around the bathroom.
The rest follows the same line. A tempered-glass platform, an integrated display to see your weight right there without having to take out your phone, and a Bluetooth connection with Wellbeinn Mate, where you can view and consult all your data.
And let me insist on this last point, because after everything we’ve discussed, it’s what really matters. A single measurement tells you nothing. A six-week trend line tells you everything. Having the series saved and being able to see the curve is exactly the right way to use a bioimpedance scale, and that’s where the app stops being an accessory and becomes half the product.
One detail that often surprises people. It has baby mode and pet mode, which calculate their weight with two weigh-ins: first by yourself, then while holding them in your arms. If you have a baby or a dog whose weight needs monitoring, you’ll know exactly why this is so useful.
Wellbeinn Balance · Bioimpedance Scale
Retractable handle so the current travels through your entire body, not just your legs. Eight parameters: weight, BMI, fat, muscle, water, bone mass, basal metabolism, and metabolic age. Tempered glass, integrated display, and Bluetooth with Wellbeinn Mate to view your history and trends.
View Wellbeinn BalanceWhat causes the most confusion when looking at the numbers
If a reading has ever left you puzzled, it's probably in this table. These are the cases that come up most often.
| What's happening to you | Why it happens | What to do |
|---|---|---|
| My body water goes up and down every day | It's normal. Hydration, meals, exercise, menstrual cycle | Compare the weekly average, not individual days |
| My body fat percentage doesn't match my doctor's | Each method uses its own formula, and bioimpedance has a margin of error compared with DEXA | Always use the same device and look at the trend, not the absolute number |
| My weight is going down, but I don't look any different | You have almost certainly lost water, not fat | Give it two to four weeks and look at the trend |
| I retain much more water before my period | A completely normal hormonal fluctuation | Don't interpret it as fat gain. It will go away on its own within days |
| My basal metabolic rate seems very low | It may be real, due to low muscle mass or age, or it may be a formula error | Build muscle through strength training. If you have fatigue or persistent cold, ask your doctor to rule out thyroid problems |
| The scale malfunctions when I'm wearing a ring or watch | Metal and poor contact with the electrodes affect the reading | Take off your shoes and remove metal objects before stepping on |
| I'm getting very different readings on two scales | Each brand calibrates its own formula | That's to be expected. Choose one and stick with it |
The essentials in four lines
Frequently asked questions about bioimpedance scales
It is a scale that, in addition to weighing you, sends a very weak, imperceptible electrical current through your body and measures the resistance it encounters as it passes through you. Because water and electrolytes conduct electricity well while fat and bone conduct it poorly, this resistance can be used to estimate how much of your weight is fat, muscle, or water. It then applies its own formula, combining that resistance with your weight, height, age, and sex. The only data it measures directly is weight; the rest are calculated estimates.
They are reliable for what they are designed for: tracking a trend over time with the same device. Compared with DEXA, the reference method, they provide reasonable estimates of total body water and moderate accuracy for fat and fat-free mass under controlled conditions. What they are not reliable for is comparing your exact number with that from another scale, your doctor, or another person, because each manufacturer calibrates its own formula.
In the morning, just after getting up and after using the bathroom, always at the same time. A normal breakfast barely changes the result according to recent studies, but a large meal or lots of liquid in the preceding hour can affect it. Avoid intense exercise, drinking alcohol, or taking a hot bath in the hours beforehand if you are going to compare it with a previous measurement. What matters is not the specific time you choose, but that it is always the same.
Once a week is more than enough to see a real trend without driving yourself crazy over the daily number. Weighing yourself every day usually creates more noise than information, because weight and especially body water fluctuate normally due to food, exercise, heat, or the menstrual cycle. What really tells you whether something is working is the trend over four or six consecutive weeks, not today's reading.
Not without your cardiologist's approval. The scale passes a small electrical current through the body and, although several studies have found no problems with implanted cardiac devices, it is still considered contraindicated as a precaution. The same applies to implantable defibrillators. If your doctor approves it, or if your scale allows you to disable bioimpedance measurement, you can at least use the weight function.
Stepping on it is not known to pose a risk, but the body fat reading has not been validated for pregnancy, so that number will not be useful to you. If your scale allows it, disable that metric and stick to weight, which is the direct measurement. And any weight change during pregnancy should be assessed with your midwife or obstetrician, not the app.
Because it is by far the most volatile parameter of all. It depends on what you had for dinner, whether you exercised, the heat, alcohol, and, for women, where you are in your cycle. A very salty dinner, an intense workout, or the days before your period can move that number without anything unusual happening in your body. Always compare the weekly average, never two individual days with each other.
The path the current takes. On a foot-to-foot scale, it enters through one foot, travels up, down, and exits through the other, so it measures your legs and estimates your torso and arms from there. On a scale with a handle or hand grips, the current completes the full circuit through your feet, torso, and arms, so the estimate is built using information from your entire body. It is not a matter of convenience; it is a real technical difference in data quality.
It compares your basal metabolic rate with the average for people of other ages. It's a motivational tool, not a clinically validated marker, so don't worry if it shows an age higher than your actual age. There is no age you can have on the inside. It's useful for getting you engaged with measuring and seeing whether your trend improves, but don't make health decisions based on that number. The best-supported parameters are weight, fat, muscle, and water.
Because BMI only divides your weight by your height squared and has no idea where that weight comes from. Someone with a lot of muscle mass may fall into the overweight category according to the WHO table while being perfectly healthy. Conversely, a sedentary person with little muscle and quite a lot of fat may have a normal weight but a higher metabolic risk. That's why parameters that do distinguish between tissues, fat, and muscle give you a much more useful picture than BMI.
Yes, as long as each person has their own profile with their age, sex, and height, because the formula uses these to calculate the rest. What isn't reliable is the body composition data for children, because the formulas are calibrated using an adult population. For them, stick to weight alone. And if someone at home has a pacemaker, is pregnant, or has metal implants in their legs, follow what we discussed above.
Eight parameters: weight, BMI, body fat, muscle mass, body water, bone mass, basal metabolic rate, and metabolic age. Body composition is estimated through bioelectrical impedance, so the most useful approach is to observe trends across measurements taken under similar conditions. You can view your history in the Wellbeinn Mate app via Bluetooth. It also has baby and pet modes, which calculate their weight from two weigh-ins: first by yourself and then while holding them in your arms.
It depends on what you want to do with the data. If you're only interested in your weight, a regular scale gives you the same number directly and costs less. A smart scale with bioelectrical impedance adds value when you want to understand whether a change in weight comes from fat, muscle, or water, which is completely different information. Think of it this way: weight that stays the same while fat decreases and muscle increases is excellent progress that a regular scale would make you interpret as stagnation.
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