Usefulness of relative measures from a scale that measures body fat?

refactored

I know absolute measurements from a scale that also measures body fat are not accurate.

But what about the relative measurements?

If the scale shows body fat trending down over time when weight stays stable, then does this mean fat is being lost or could other factors be at play?

tomcustombuilder

Those scales, and pretty much every measuring devise can't differentiate between fat and water. Keep measurements around where your body holds the most fat, which is usually hips or at the navel. If that measurement is going down, you're losing fat.

nossmf

I believe @tomcustombuilder is referring to using a tape measure to record inches/centimeters. Since muscle takes less space than the same weight in fat, when combined with weight you can get a gauge on fat gain/loss. i.e. if you weigh the same, but your waist is smaller, odds are you've replaced some fat with muscle which weighs the same but is slimmer.

AnnPT77

Other factors can be in play. It's maybe OK for a gross trend line over a long time period IMO, if you ignore outlier readings, and don't read too much into small variations. I think it can be useful to convert the scale's estimated BF% into estimated BF pounds, lean pounds . . . at least for me, that makes it easier to suss out truly improbable variations/outliers. I wouldn't put a lot of store on it, but it's one more data point, in conjunction with tape measurements, occasional same-pose/clothes front/back/side photos, estimates from the "Navy body fat calculator" kinds of things (the more measurements input, the better), caliper estimates from an experienced person (if you have that option), and that sort of thing.

tomcustombuilder

nossmf wrote: »

I believe @tomcustombuilder is referring to using a tape measure to record inches/centimeters. Since muscle takes less space than the same weight in fat, when combined with weight you can get a gauge on fat gain/loss. i.e. if you weigh the same, but your waist is smaller, odds are you've replaced some fat with muscle which weighs the same but is slimmer.

Correct. Those cloth tapes for sewing or Amazon has those small roll up tapes that are made for this. As a generalization, 1" of loss at the navel will represent around 5-7 lbs of fat loss. Your results may vary...

PAV8888

while holding the tape straight to the ground, while figuring out the same exhale or inhale... or instead of navel finding the midpoint between the iliac crest and your lowest rib... not trivial, IMHO.

I generally don't believe the bio-impedence measurements by two point electronic scales. Especially if both weight and body fat are trending down... because hey: both WOULD trend down.

HOWEVER. Under the specific conditions you discussed? Generally stable weight over months with body fat changing? Especially if you're doing things that give you reason to believe this might be true? Putting someone else on there and seeing a completely different number but similarly "reliable" results where things seem to be working as expected... then I would be tempted to start believing that trend!

cmriverside

because hey: both WOULD trend down.

Exactly this. Unless there is some reason (and, a bodybuilding competition is the only reason I can think of) then what's the point in doing some random water measurement masquerading as body fat?

I mean. I lost 80ish pounds without knowing what my body fat is or was. Still don't know, 15 years later. Also don't care.

You will be losing mostly body fat if you're losing weight. There will also be loss of muscle and connective tissue. There will be fluctuating water weight.

Just do the next right thing. It's not important to major in the minors.

mtaratoot

I have a bio-electrical impedance analysis function on one of my scales. Do I trust the number as accurate? Hell no. But do I trust that over the long term that the trends are? Hell yes. Is the number precise? Oh sure. It gives me a number to 0.1%. But as far as accurate, I don't think so.

Over time, it has trended generally with weight; that makes sense.

I am thinking that after all these years, the sensors may be failing, and when it finally does fail, I may not replace it. It also tells me bone density. The algorithm seems to track along with weight; I know what weight it will tick up or down. It also tracks with age; I get a year older, and it changes.

So the important question is do I trust it? Well only the long term trend. I also have a caliper, and it tends to give similar results. That said, using a caliper is an expert system, and it's not impossible that I, as the user, am getting readings that match the scale with an unintentional bias.

kshama2001

Just jumping in to say hello from another creamsicle cat parent

PAV8888

Dem cats are cute!