Body fat/body composition scales

Try this:

1. Buy a bottle of water (1L is good) and find a set of these scales to test.

2. Before drinking the water, weigh yourself, check the fat % and note it down.

3. Drink said bottle of water.

4. Step back on the scales when the water is gone and note the change in the body fat %.

Now I'm no scientist, my B.A (Hons) was in the arts field, but even I know water can't change your body fat level on intake. 

These machines are not accurate, they rely on you having not just similar, but the exact same level of hydration each time you step on the scales and lets face it, unless your a machine and monitor exactly how much you drink- and eat (because food contains water) and sweat and breathe (breath contains water vapour) then your never going to get an accurate result. And when your looking to retain a % within a 5%  range your wasting your time. Just go by the callipers and tape measurements. 

I get mine down to its minimum of 5% , I doubt it to be correct.

It doesn't measure body fat or body fat percentage at all. They actually pass an electric current through the body between the two contact points and measure electrical impedance - which is hugely affected by how well hydrated you are. This is then converted (making a number of pretty large assumptions) into a calculated % body fat.

an adult weighing 100 kg should have a change of the order ~ 1% body fat if they measured before & after drinking 1L water. Anyone care to bet if that would be all you'd see? I'd put money on a decrease of more than 1%, and it would be due to the hydration level changing, not the body composition changing. 

I'd guess that if they're used well they can give you a precise reading, but I'd doubt they're very accurate. Useful for a trend, at a push. And for the same effort in rigour of usage, you'd be better saving the dish & getting a pair of calipers. 

SnailGirl - well for once, I am going to disagree with the majority of the posters above. The thing about body composition scales is you have to know what the output means. All this talk about reliability is pretty pointless if you expect them to give you a foolproof, highly accurate one-time measurement. They don't work like that.

What they are EXCELLENT at doing, is showing you a trend IF you measure yourself consistently.

For the last 4 years or so, I get up in the morning, have a pee, then use the scales. After that, I can eat and drink. I record this data and have very meaningful graphs which correlate well with my exercise activities. I realise that no one particular snapshot is going to be perfectly accurate, but that the trend of data IS reliable (and helpful!).

I use Omron BF-500 scales, think they have been replaced by the 510. A number of other threaders use them and find them helpful. Think I paid between £30-40 for them which i reckon is a bargain. One feature which is particularly useful is that they can provide an estimation of how much visceral fat you have. This is the dangerous stuff around the waist which tends to compress and limit the function of your internal organs. Yes, there are plenty of other manufacturers out there but I can only talk about the ones I bought (so please no comments about bias or other such nonsense!). Cheers, TD.

Thanks to all of you for your advice and valuable observations, most helpful. The main reason I am thinking about getting these is because my other scales have just packed up and I need to replace them so I thought I would investigate getting some with added features purely because one can these days! I had my Body Composition read at the VLM Expo and granted their scales are FAR more accurate, I found it fascinating. I've just started following the online Weightwatchers ProPoints plan after having enjoyed my downtime a bit too much from doing VLM so I will be measuring and keeping an eye on intake like a hawk. I'm pretty good at being well hydrated and like Tricky Dicky I have a morning routine that I stick to so SHOULD get consistent results... perhaps!

I got mine from poundland. It's just a hand held one, but gives me near enough the same result wheneverI use it. I choose not to believe it as it's higher than I want the answer to be!

Sussex Runner (NLR). Well one of us knows what we are talking about and the other one is postulating wildly. Your choice what you name it dear  

One of the pleasures of training is being able to quantiy the results. You can do this with a stopwatch, a cadence meter, a heart rate monitor AND.... with a body composition monitor. They all measure different things, with varying degrees of accuracy.

I don't hear anybody on this forum saying we should all drop our GPS watches down the toilet because they are only 98% accurate (which I might add, is a greater level of inaccuracy than what is claimed on the set of scales in my bathroom).

My point is that the GPS watches tell you something inaccurately

Inaccuracy is acceptable, as long as you have an appreciation for deviation... and I'm sure you do.

Sure, I'd rather have running data than weight or body fat data, but then again, I have the possibility of both. So why not? Actually, I'm in an interesting position right now. I PB'd 2 months ago in my last mara (at least i could rely on good accuracy from my Garmin for the time - 2h54). But a couple of weeks after I felt like I had a stiff knee.

Well the long and the short of it is that I've just had an operation on that knee and haven't been running for six weeks, just managed a bit of painful cycling and swimming. Having the body composition monitor has let me keep track of what is happening with my body as I de-condition (it feels more like decomposing at times!!).

Prior to the mara I was around 9% body fat, these days I am nudging towards 12%, but I have only gained a kg. My Garmin isn't telling me anything at all.

Hope this is helping SnailGirl (if you are still here). Cheers everyone.

Yeah but there's inaccuracy and then just being very wrong!

I used one of these fat % machines (or rather, my gym used one on me), the before level was 21% and when I was done, being somewhat more hydrated due to downing almost 2L of fluid, was a reading of 27%! And that was only 2 hours apart! -So exercise gained me more body fat?

Now I know the GPS thing will have some inaccuracy but you can still get the general gist of it and be near enough OK. But being that your looking to be within a range of about 5% and just 1% can make a big difference (in or out of range for example) where as even 5% mileage isn't going to have the same significance.

jennn wrote (see)

Yeah but there's inaccuracy and then just being very wrong!

 

I used one of these fat % machines (or rather, my gym used one on me), the before level was 21% and when I was done, being somewhat more hydrated due to downing almost 2L of fluid, was a reading of 27%! And that was only 2 hours apart! -So exercise gained me more body fat?

 

Now I know the GPS thing will have some inaccuracy but you can still get the general gist of it and be near enough OK. But being that your looking to be within a range of about 5% and just 1% can make a big difference (in or out of range for example) where as even 5% mileage isn't going to have the same significance.

All you've proved jennn is that the people who work in your gym are a bit thick.

Given that these body composition monitors work via timing of electrical conductivity, they are VERY sensitive. So if you change the amount of water in the body, or you change the degree of conductivity of the body (more electrolytes/ less electrolytes etc.), or you change the conducitivity on the skin surface (sweat) then this is going to affect the result.

Remember I said I use it the same time every morning after removing all variables - no pee in bladder, no drinks, no food, no sweat? There's a reason for it. Can't people get over their prejudicies with reasonable logic? A highly accurate machine used wrongly is probably more misleading than an inaccurate machine used correctly.

Tricky Dicky¹ wrote (see)

The thing about body composition scales is you have to know what the output means. All this talk about reliability is pretty pointless if you expect them to give you a foolproof, highly accurate one-time measurement. They don't work like that.

What they are EXCELLENT at doing, is showing you a trend IF you measure yourself consistently.

I agree with Tricky on this.

Yes the absolute value may be inaccurate by a few percent so it's not worth comparing against measurements made by different devices or methods, and yes there are so many variables which mean it's daft to compare one person against another even on the same scales, but if you keep the variables relatively consistent then the trend over time is still meaningful.

I use mine in the morning, after a visit to the loo, before breakfast, and the results seem to have a small degree of variance from day to day, and once which tends to make sense according to the quality of training/nutrition/hydration the day before. To me it's a more useful indicator than the crock that is BMI anyway!

Interesting read. Do I trust them to be accurate no ? I however bought some salter Mibody scales (woeful battery life) but I used them weekly or a couple of times a week over a period where I started running and trained for my first 10km through to doing 20km and Hellrunner. Apart from running I was playing tennis, racketball (fantastic cardio..) and I tried to be more sensible with my diet. I dropped from 101kg to 86kg and  obviously made great performance gains over that period. The graphs that were created from the data recorded may not have been 100% active but they certainly matched the progress I made. Like Tricky I weighed myself under similar conditions at the same time knowing full well what a kg of food does to your weight or a kg crap. I found that the scales helped me to understand how my body was responding and helped motivate me. It is not worth weighing yourself daily at varying times because more often that not I just see this as a demotivator for some. They see stable weight or perhaps minor gains and they give up. Plan achievable and realistic targets over longer periods and you will achieve them and keep motivated.

Sussex Runner (NLR) wrote (see)

Like your style Tricky Dick. But your analogy fails. GPS watches tell us how far we run, which is a very useful thing to know. How many training logs ask runners to put in your body fat percentage ?

Mine does.

Tricky Dicky¹ wrote (see)

 

Inaccuracy is acceptable, as long as you have an appreciation for deviation... and I'm sure you do.

 

Best put down ever! lol

I have body fat scales, but I don't use that function. I can appreciate that they show a trend whilst not needing to be 100% accurate, but the simple truth is that I can see for myself whether i've got thinner or fatter. And long term I find the best method is taking photographs.