i don't get it
this post was submitted on 06 Apr 2025
121 points (99.2% liked)
Memes
49460 readers
1383 users here now
Rules:
- Be civil and nice.
- Try not to excessively repost, as a rule of thumb, wait at least 2 months to do it if you have to.
founded 6 years ago
MODERATORS
Those things are totally bogus if it makes you feel any better. Changes in body composition are not reflected properly via bioelectric impedance.
Truth is every bf% measurement is pretty much just a guess with a huge range of error. Far more practical to find some other measurement to track, such as athletic performance (lifting, cardio times) while keeping a loose eye on your weight
Are you saying that digital scales used to measure the weight of a person are inaccurate or am I mixing topics? This is new to me. Why measuring weight should be hard/inaccurate?
And why analogic scales (if they can be called like that) are better?
No, they are talking about weights that spits out a body fat percentage alongside the weight.
The other response is correct. Many “smart” scales claim to be able to tell you not only your weight, but also what percentage of your weight is lean mass vs body fat.
They are not accurate in that respect and should never be used
Normal scales that just tell you your weight, whether digital or analogue, are generally correct and reliable
They're not accurate but I think they can at least track trends consistently. A clock that's five hours ahead still tells you how much time has passed relative to itself. Similarly a scale might tell you what direction your fat level is trending.
I think they can at least track trends consistently
I'm sorry to say, but they can't. It would be one thing if, for you as an individual, the error was always consistent (e.g., "always five hours ahead"). Then at least you would be able to track trends over time. Sadly, the technology itself is not reliable in that way and should never be relied on to track trends.
Perhaps not. My subjective experience of my Withings scale is that the reported fat percentage has at least remained where I've expected given my general activity level. ie, fat percentage goes up when I'm sedentary, down when I'm active.
But it's more a curiosity than a useful metric regardless.
I strongly encourage you to disregard the bf% information that scale provides you, even if it is only a passing curiosity. It can and will taint your general understanding of the body and your relationship with fitness. I would recommend even disabling it entirely if possible, and would even recommend replacing it with a non-"smart" scale if the option is at all economical for you. I'm happy to explore the subject further and suggest alternatives if you so desire
Honestly I don't care enough. If I happen to be in the interface I'll probably turn it off, sure. It doesn't inform any decisions, I barely register that the number exists.
It doesn’t inform any decisions
Excellent, I encourage you to never deviate from this path
This may be true for most brands/scales, though the Omron body composition scales where you hold the handlebars are clinically validated and used in research
Impedance body fat analysis had a lot of problems, I'll just get into one:
The measurements, even the palm to feet ones on big machines in medical settings with handles, are based on a known level of how much human skin conducts electric currents. I'm part of a genetic group that I'm missing one of the 5 types of collagen and so my skin conducts electricity differently and the impedance machine gives me the exact same 44% BF reading regardless of my actual weight. My doctor had to tell me that impedance BF measurements will never be accurate for me so I have to have a DEXA or skin fold if I want to know for sure. This would have been fine if I hadn't already spent years believing those fucking devices that thinking that even though I was losing fat, I must be doing something wrong be the impedance scale didn't change as they were "scientific".
They aren't that accurate for the whole population, and we don't actually know what percentage of the population they are accurate for because no one has bothered to check.
Apologies, but the Omrom scales are a fundamentally worthless scam. I strongly discourage you from relying on them for any purpose relating to bf%, and strongly encourage you to disregard any information you receive from sources that imply the information they provide you is worthwhile. It's incredibly common for the handlebar bioelectric impedance devices to be used in gym contexts to try and push personal training ("Free consultation including a bodyfat scan!"). I additionally encourage you to discontinue your subscription to any gym that offers this, and leave them a negative review specifying why you left.
The fitness industry is bursting with many such scams. I advise you to disregard them all. I'm happy to delve into this subject in as much depth as you may be interested in
Which parts of their business are a scam?
Blood pressure monitors? TENs equipment? Or just scales?
Do you have any source on why they are entirely unusable? Why are they used in research?
Which parts of their business are a scam?
The bioelectric impedance scales, as I have been consistently saying the entire time. I have no expertise or opinion about their other products. It's entirely plausible that they may furnish you with a functional blood pressure device, but to be honest I am reticent to support any company that offers scam products alongside their legitimate options.
Why are they used in research?
Whoever severely misled you into believing that this company's products are some important cornerstone of scientific research should be totally exiled from your consideration. Hopefully it's only a result of their ridiculous marketing and this will be a simple correction
Do you have any source on why they are entirely unusable?
You are the one claiming they are not only usable but scientifically important, please feel free to furnish any sources proving they can tell your bf% better than +/-5%. The reason you can't find any is because none of the the methods, including DEXA scans, are functionally accurate at all. The entire field exists to scam people who are trying to better themselves
man i largely agree with what you are saying and there are tons of useless 'fitness' products.
but you cannot claim to be "happy to delve into the subject" and when asked for sources simply deflect. you have to remember, that absence of evidence is not evidence of absence.
so if you want to believabily present yourself as an expert on the subject and have such an absolute standpoint - you need to present some good reasons. otherwise you have to soften your standpoint to something akin to: "there has ben no proof of its reliability". everything stronger seems disingenuous.
The irony being that these companies pushing the scam products are themselves presenting as experts with an absolute standpoint. A standpoint which of course involves paying them a bunch of money to acquire extremely specific capabilities which are totally unfounded in reality.
Which makes you raising this principle very interesting: absence of evidence is not evidence of absence. You are misapplying the concept.
If I said, "there are no bears in the woods", then yes now I have to carefully and thoroughly demonstrate this. An impossible task in fact, since I simply cannot check behind every tree. Indeed, even if I did check every tree, bears move around, and I could miss one despite it really being there! Therefore it is wrong for me argue such a strong negative, and it would be proper to instead say, "I haven't seen any bears". I'm with you on this.
Now imagine if some company says, "The woods are full of dangerous bears! You should buy our bear repelling hat!", and I say, "This is actually a well known scam tactic, and this company is just selling useless hats. Another company is selling bear pants, and yet another company is doing shoes. It's all bullshit. Don't waste your money. Use proven methods such as bear spray."
Now in this situation, sure, you can try to start a semantic argument with me about whether or not it is philosophically just for me to state "the hats are useless" in such absolute terms. Structurally, that snippet is the same, yes? A strongly phrased negative. Doesn't it run into the same problem?
It turns out, no. You see, the scam company at this point in time has already made the claim that the hats are useful. This is a claim that absolutely requires a source. The fact that they are forcefully presenting this claim despite having no source is itself proof that the product is a scam. By the very nature of the phenomenon in question, there needs to be a source before they make the claims.
In other words, once a company is claiming that an effect is present in fact, then absence of evidence becomes evidence of absence. Because they are simply fucking lying lol. We don't need to keep doing this every week with every company that runs the same scam template with a different article of clothing.
Anyway, you wound me with your incorrect assertion that I have deflected anything, when I directly answered the questions I was asked and provided further information on things to look into, such as DEXA scans. Anyone bothered by my strong language will quickly discover the reality that every reputable study ever performed relating to these devices recommends against them.
Skin fold isn’t necessary accurate but it is repeatable. I’d you measure the same spots the same way you can tell if you are gaining or losing fat.
Skin fold calipers, in the best possible case scenario when administered by a trained expert, have such a significant margin of error as to make them functionally useless. I strongly discourage you from lending any credence whatsoever to their measurements when determining your plans regarding training and nutrition.
See my other comment regarding the smart scales, but it's the same situation. They're not "always consistently wrong by the same amount" per individual. If so, then yes, that would be useful for tracking trends. Sadly they are not
As an amateur who has used them enough to get repeatable results, I strongly disagree with you. Yes they are not accurate but they can be precise enough to track progress when the scale is flat or up due to a recomp.
You can certainly pinch the same spot on the same day and get the same number a few times in a row, sure. But as your body changes you become a different organism. It’s not always going to be consistently wrong in the same way. Self administering the skin fold test makes the problem even worse.
Setting aside the fact that they are neither precise nor accurate at tracking trends, why are you recomping?
No really, let’s think about why you’re changing your body. Is it for a strength sport? Is it to improve your health? Is it to become more muscular? Do you want to run faster?
Because all of these things are completely self evident. Simply take a step back and examine whether or not you are actually making progress towards your goals. Whether you are stronger, faster, etc. If your doctor is happy with your new bloodwork.
All of the various bf% scams are so ridiculous at the outset because in fitness, we have such specific tangible goals. There’s no situation where having a figure for your bf% actually assists or informs you in any way. If you are achieving your goals in fact then the number shouldn’t dissuade you. If you are not achieving your goals in fact, then you shouldn’t let the number gaslight you about it and make you feel better. You need to make adjustments based on your actual results, not on something as nebulous and abstracted as bf%.
Especially not when the best, most expensive methods can at best tell you your number within six percent. Which is completely absurd. That 8% vs 14%. Literally guessing a number while looking in a mirror is more accurate for the purpose of tracking progress
I don’t care if the calculated % is wrong and I don’t believe you about changes in error. A thinner subcutaneous fat layer will form a thinner pinch at the same load. I am aware that it is an indirect measure but nonetheless it helps me meet my goals.
What is there to believe or disbelieve when the problems of this method are so incredibly well documented? The body is not as simple as you’re portraying, the measurement can swing in either direction for many reasons over the course of months and years. Rely on these measurements at your own peril
I'm 75% anxiety.