you don’t seem to get my point entirely, so ill try to explain it here. your standpoint seems to be:

• body fat cannot be determined by impedance
• the measurements are that unreliable that the mere presence of the measurement hurts more than it helps

you present these points as expert, not as your opinion. in the comment thread you write: “I’m happy to delve into this subject in as much depth as you may be interested in”. when someone asks you for sources, supporting these points (presumably because they are interested) - you deflect and take a combative stance. it is deflection, as you ask the person trying to learn something, to find proof that your point is wrong. since you (initially) did not provide sources for your points - you seem to take the absence of evidence (from the companies selling these) as evidence, that it can not work and will cause harm.

This line of argumentation makes me second guess your motivation. even though i agree with the overall viewpoint. i am not asking you to prove it is a scam. as you mentioned it is tedious and wasteful to prove every new scam attempt false. so if you shift your argumentation just slightly (which you did in your reply to me), the whole second guessing of motivation won’t occur:

• The companies selling these products don’t provide any proof, that these scales work as advertised
• especially in medicine it is required to proof, that the benefits hugely outweigh the drawbacks
• who is more likely to tell you a falsehood: the person actively trying to sell you something or the one not selling anything?
  • -> be more skeptical of the person with a motivation to mislead you and ask them to provide proof and sources

these points are a very strong argument IMO and don’t require to do any more research. but they seem much more genuine as you don’t appear go back on wanting to discuss the subject and don’t take a combative stance towards the person probably trying to learn something.

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.

there should be a rule that, if you sell stuff, which produces rubbis - you have to provide enough bins for said trash.