Water retention and stats

jelleigh

A curiosity question that may just reveal my poor math skills:
Every two weeks I get a body scan at a metabolic clinic I'm visiting and they give me a printout that showed the following
- bmi
- bmr
- impedance
- fat %
- fat mass
- ffm
- tbw
I don't know what ffm and tbw stand for but anyhow. I'm losing weight quickly this first week due to low carb. If I want to see how much of it was fat and how much was water weight, I should see that refle in the fat mass category yes? Like if I've lost 7 lbs but my fatty mass had only gone down by 3 then it's really just 3lbs lost?
I asked the doctor about the accuracy of theses scales (it's the type you stand on with the metal plates to measure the electrical flow and determine fat% - not sure what they are called) because I hear they are notoriously skewed, but he assures me that this is a hospital grade very expensive machine and that the margin of error is very small.

Edited for spelling

SnifterPug

I'm guessing ffm is fat free mass and tbw is total body weight. And yes, the fat mass is the number you want to see reducing. Anything else lost will either be water weight or lean body mass (mainly muscle). It's highly unlikely you will only lose fat. Even losing a much higher proportion of fat than lean body mass can be difficult. Don't let that discourage you.

jelleigh

Ok good point. So what is an average or decent ratio to lose each category at? I'm trying to minimize muscle loss of course (hitting a protein goal and weight lifting) but what would be considered "normal" for a 39 year old female? Like 1:1 muscle:fat loss? (That seems bad)

MikePTY

jelleigh wrote: »

A curiosity question that may just reveal my poor math skills:
Every two weeks I get a body scan at a metabolic clinic I'm visiting and they give me a printout that showed the following
- bmi
- bmr
- impedance
- fat %
- fat mass
- ffm
- tbw
I don't know what ffm and tbw stand for but anyhow. I'm losing weight quickly this first week due to low carb. If I want to see how much of it was fat and how much was water weight, I should see that refle in the fat mass category yes? Like if I've lost 7 lbs but my fatty mass had only gone down by 3 then it's really just 3lbs lost?
I asked the doctor about the accuracy of theses scales (it's the type you stand on with the metal plates to measure the electrical flow and determine fat% - not sure what they are called) because I hear they are notoriously skewed, but he assures me that this is a hospital grade very expensive machine and that the margin of error is very small.

Edited for spelling

Even hospital grade machines, while they have less error than a home one, still have a decent enough margin of error that you will not be able to see something as precise as "how much of my 7 pound loss was fat vs water". That is not what they are intended for. They are intended for long term trending, which they can be useful for. But there is always going to be enough fluctuation that they are not effective in trying to be that precise.

AnnPT77

jelleigh wrote: »

Ok good point. So what is an average or decent ratio to lose each category at? I'm trying to minimize muscle loss of course (hitting a protein goal and weight lifting) but what would be considered "normal" for a 39 year old female? Like 1:1 muscle:fat loss? (That seems bad)

Doing what you're doing, major/material muscle loss isn't very likely.

If you lose a lot of weight, you'll lose some lean mass. A smaller body requires less skin, fewer blood vessels, less volume of blood, etc. No big deal, in other words. Muscle is part of lean mass, but there are other tissues in that, too.

I've seen numbers like 25% of weight loss from lean mass as a generality, which I assume averages in stats on people not strength training, not losing at a sensibly slow rate, not getting enough protein, getting poor overall nutrition, etc.

No matter what your doctor's saying about the very expensive device, there's a margin of error, and things like hydration affect the results.

Thought experiment: What would you do differently to further reduce the risk of muscle loss, that you're not doing now? If the answer is "nothing", why worry further? It's just stressful, stress can increase cortisol, cortisol can add water weight . . . ( <== true, but fairly trivial: I'm mostly just joking around here).

After saying that, I'd reinforce that the loss of needed functional muscle will be minimal, if losing at a sensible rate, continuing (or starting! ) to use your muscles (like strength training), and getting good nutrition (especially protein, but also generally.

It's going to be hard to quantify, but please try not to worry! :flowerforyou:

jelleigh

So I just went to the clinic and although I'm down 4 lbs (actually 6 without the extra 2 lbs clothes) it's apparently all water weight. No movement on fat mass at all. I'm trying not to be disappointed but I feel like the progress I was happy about is no real progress at all.
Ok. Done my whining now.

Silentpadna

jelleigh wrote: »

So I just went to the clinic and although I'm down 4 lbs (actually 6 without the extra 2 lbs clothes) it's apparently all water weight. No movement on fat mass at all. I'm trying not to be disappointed but I feel like the progress I was happy about is no real progress at all.
Ok. Done my whining now.

Two weeks between scans is not a lot of time. If you are truly in a deficit - over time - your fat loss should correspond roughly with that, while everything else fluctuates. If you scan for 8-12 weeks (longer if you have less to lose), you should be able to see some sort of trend - which by the way would show up similarly on a bathroom scale.

PAV8888

It is not unexpected that if you low carb most of the mass lost will be non fat mass. Conversely when you stop low-carbing the associated gain in mass is also non fat. You're actually manipulating "water weight".

To be more precise you're depleting and replenishing your glycogen stores of ready energy which consist of one gram of carbohydrate bound to 3 grams of water.

So each four calories of energy that you lose or regain when introducing or coming out of a low carb state represent 4 grams of mass change on your scale, 1 gram for the carbohydrate and three for the water it is bound to.

This leads us to conclude:
- the initial weight loss when starting on low-carb is an illusion and so is the initial weight gain when stopping
- you're majoring in the minors and worrying unnecessarily, just as Anne discussed above (in terms of the worrying)

To further expand on that. Are you establishing for yourself a reasonable deficit, ensuring you have an adequate supply of protein, and engaging in sufficient strength training and muscle stimulation? If yes then you're doing everything you can be doing and there's nothing more to worry about!

Good fat loss ratios could range from anywhere like 10 to 1 in terms of fat to lean mass lost for someone who is starting out with obese levels of energy reserves, to achieving no worse than one to one for someone who is already very lean.

I think that anything along the lines of 3 to 1 or even 2 to 1 when close or within the normal weight range will actually be quite good.

I also note that most of the generally available machines for estimating body composition have margins of error that make a lot of these calculations meaningless to a substantial degree.

Even if you were willing to pay the radiation cost of CT scans, the image interpretations could still have a 2-3% error, and MRIs would be slightly higher errors and a substantial cost to administer and interpret. Dxa scans and dunk tests would come next and only after that would we be considering body pods and calipers and multi-point bioimpedance. Single point bio impedance would be at the far bottom of the heap in terms of accuracy and consistency. Regardless of whatever the person selling you tells you.

lorrpb

jelleigh wrote: »

So I just went to the clinic and although I'm down 4 lbs (actually 6 without the extra 2 lbs clothes) it's apparently all water weight. No movement on fat mass at all. I'm trying not to be disappointed but I feel like the progress I was happy about is no real progress at all.
Ok. Done my whining now.

So this is an example of why you can’t rely on this type of “estimation“. Per all the comments above. Just keep following your plan for a few more weeks and focus on the total number.

sijomial

Has the clinic told you what you should and shouldn't do on the day (and preceeding day) of the test to minimise the known issues with using electrical resistance to try and estimate body composition?

Overall I must say you are putting far too much emphasis on the readings you are getting. Do the right things in terms of effective resistance training, protein intake and rate of weight loss and good results will follow whatever your machine tells you every fortnight.

I get free use of a commercial grade BIA device at my gym and although its trend is believeable there are often plainly impossible short term variations of both fat and muscle mass. The two pounds of muscle gain it shows in days will most likely be matched by a sudden 2lb loss of muscle next reading.
Treat the data as interesting, perhaps showing a true trend over time and sometimes downright amusing and you won't go far wrong!

PS - Your Doctor is mistaken about the margin of error, a lot of the error comes from being used in inappropriate and varied conditions though. He should know this which makes me wonder about his impartiality.

jelleigh

Thanks for the input everyone.
I know the long haul is what's important so I'm going to stick to the course either way. But I'm a huge data nerd and although trending us what's important instead of singular data points, I still am surprised that the was seemingly no movement on the fat. I was already eating relatively low carb before starting this (50-100 g a day) so I wouldn't expect as much of a water woosh add someone who was a chronic bread/pasta/sweets consumer.
@sijomial I'm curious about what the actual%play would be? Wouldn't it be particular to the specific machine used? My understanding is that the bio impedance scales that gyms often have aren't of the same calibre as medical grade stuff. For example I know the scales in the hemodialysis unit of the hospital I work can't be compared to even an expensive home scale.

I was thinking of dexa (again just cause I'm curious) but my doctor was strongly not in favor of them. He says the radiation exposure is equivalent to 200 xrays and he wouldn't recommend. I haven't done enough research to decide what I think of that.

Pipsqueak1965

There's not really any point spending more money on it. If you work out hard and eat at a bit of a deficit, you know you will lose some fat.

sijomial

jelleigh wrote: »

Thanks for the input everyone.
I know the long haul is what's important so I'm going to stick to the course either way. But I'm a huge data nerd and although trending us what's important instead of singular data points, I still am surprised that the was seemingly no movement on the fat. I was already eating relatively low carb before starting this (50-100 g a day) so I wouldn't expect as much of a water woosh add someone who was a chronic bread/pasta/sweets consumer.
@sijomial I'm curious about what the actual%play would be? Wouldn't it be particular to the specific machine used? My understanding is that the bio impedance scales that gyms often have aren't of the same calibre as medical grade stuff. For example I know the scales in the hemodialysis unit of the hospital I work can't be compared to even an expensive home scale.

I was thinking of dexa (again just cause I'm curious) but my doctor was strongly not in favor of them. He says the radiation exposure is equivalent to 200 xrays and he wouldn't recommend. I haven't done enough research to decide what I think of that.

I think a few seconds doing research would disprove your Doctor!!
Not impressed with his advice on two counts now, that comes across as both wrong and scaremongering.

Yes different machines will give different readings. More up to date multi-frequency ones have a higher chance of accuracy compared to old fashioned single frequency. A big difference will be if the machine is measuring whole body or just half your body (feet and hand sensors or just hand/just feet sensors).
Just because it's in a clinic doesn't mean it's any better than the multi-frequency commercial grade machine in my gym.

As a "data nerd" first you have to think what the data is - a measure of electrical resistance, not a direct measure of fat or muscle. And your hydration levels, which mess up the consistency of the results badly, are affected by a lot more than just your carb intake. Your clinic should have told you how to minimise those variations.

jelleigh

Thanks for the added info @sijomial . Yes they did give me instructions on how to minimize the error factor including being well hydrated. So I guess at least they got that right lol