Lemon's paper includes sedentary people. http://i2.wp.com/bayesianbodybuildi...esize=420%2C301

Agreed. We need data. This will be expensive.

Unfortunately, if there really is an mTOR pathway and if what Rosedale and other researchers affirm is true, the metabolic master switch is triggered beyond a certain threshold of proteins concentration, independently of our enjoyments or hunger or consternation or whatsoever other individual feelings.

As I understand, nobody really knows the exact threshold of mTOR activation, although the actuation signal is definitely an abundance of proteins, definitely more than the body needs. this means, more than the individual minimum requirement. A little more? Probably mTOR stays put. Much more? mTOR awakes. How much more? 10%? 20%? 50%? I'm not aware of any suggestions in this direction.

How other posters have written, if we do not own a medical lab, probably the only way to find our neutral nitrogen balance point is by trial and error.

I just had this thought, if those fitness scales which measure bodyfat by electrical resistivity are enough accurate, we may have a good reference.
We'd just need to decrease our intake of proteins, all other things being equal, until we start loosing lean muscle mass, parameter which the scale will measure (I just checked). At this point, if the trend slowly goes down, than we can reasonably assume that we crossed the border and are in a negative nitrogen balance. We write down our proteic intake. After we are sure it's not some anomaly or oscillation, then we increase a little our proteins intake; if the muscle mass returns to its previous value, we write this other proteic intake. Now we know that our minimum protein requirement is in between the values which we wrote down, correspondent to negative and positive balance.
It sure takes some patience but, to the cost of being commonplace, life wasn't meant to be easy, and most of you guys know that well.

Now, if you guys do not find any substantial flaws in my reasoning, I'm ready to buy one of them scales, they are pretty and they measure a few interesting parameters related to bodyweight.

I'd be careful with these scales. Tests indicate highly inaccurate, inconsistent results. However, it's plausible that you could use a good quality scale of this type to identify an initial benchmark, and then identify changes based on protein consumption. You wouldn't necessarily get an accurate fat composition measurement; rather, you'd be tracking deltas from the previous benchmark based on known protein consumption.

Yes, well, assuming those deltas are accurate, I can live with an instrumental bias. My concern though are the inconsistent results you are citing.

Thsi is another method I just looked up which sounds pretty simple, of course it's an estimate and I would repeat it a few times to be sure. I have no idea of the accuracy of teh math beyond teh suggested parameters.
From www.allmaxnutrition.com

Right, you'd need to know whether the scales are making an accurate distinction between lean mass, fat mass, and water. I'm not sure those key distinctions are at the pay grade (price) of these scales, as these subtleties are important and likely require a more expensive measurement solution. There's a debate about how accurate DEXA scans are in relation to those distinctions. Not sure a household fat scale would suffice in that realm.

GRB5111, medical people do say DEXA scans are pretty accurate, but sure we can have doubts about nonexpensive scales (I saw some apparently good ones at about 80 or 90 US$).

In the meanwhile I'm exploring the analytical method above posted.

thanks for posting the plot, now i'd be curious to know whether that 0.8 g kg-1 d-1 for sedentary people is the default RDI or something Lemon measured himself. it is a threshold beyond which rate of protein synthesis reaches a plateau, if I guessed it right.

I've never seen the original data. I suppose I could get the paper on Monday.

On the x-axis is protein consumption. On the y-axis is synthesis and when the synthesis goes asymptotic then the protein consumption is adequate. That's where 0.8g/kg comes from. Before this thread what struck me about that conclusion was the huge spread from the first sedentary data point at ~0.5 an the second at 1.0g/kg. It didn't leave me very confident in 0.8 being just right.

In light of this thread, I think another interesting thing is the spread between sedentary, those doing aerobic training and those doing anaerobic training. A little bit of exercise causes a huge amount of variation in protein needs. So maybe it's just as teaser said four or five pages ago. Maybe without enough protein, our bodies fail to fully regenerate and we get weaker thus discouraging high load activity. That is, our lean mass varies to mach our insufficient protein intake. I am confident there is some sort of regulating mechanism. What it is though is pure speculation on my part.

Urinary samples for nitrogen balance must apparently be collected in controlled setups. Many errors are possible as this researcher points out:

I just saw the Tarnopolski et al. study, 1988. It shows that strenght athletes (bodybuilders) are still in slight positive balance at 1.0 g/kg/d whereas endurance athletes would need more proteins than strenght athletes.
This goes against the conclusions of Lemon's study, but maybe it is just to show how huge variations we may expect and how little we can depend on literature in our individual cases. Apparently, bodybuilders would be able to sequestrate nitrogen very efficiently. Protein powder would be a mere business, actually useless towards muscular growth if just enough real food is taken.

The relevant book section should appear by clicking this search URL:

https://books.google.it/books?id=xR...balance&f=false

By coincidence I had some comparative tests done just this past week, which might be of interest to this discussion.
Last Tuesday I went to a clinic that measures body composition using a bioelectrical impedance device called DF50 and it reports fat mass, active tissue mass and hydration status.

The household scales, which measure body fat, also use bioelectrical impedance but are less accurate. (After all you get what you pay for. I don’t know what a brand new DF50 costs but there is currently a second hand one on eBay selling for US$925 DF50 on eBay )

Of course the clinics that do these tests always swear that the results are accurate but being a curious type of person I like to check. So last Thursday I went to a different clinic to have a DEXA scan.

Here are the results of these two separate tests:

Bio-impedance DF50
Total Mass (TM): 69.0 kg (Clothed but without shoes. No deduction was made for mass of clothing, which I measured at home to be 1.5kg)
Fat Mass (FM): 17.1 kg
Active Tissue Mass (ATM): 28.1 kg
Extracellular Mass (ECM): 23.7 kg
Fat Free Mass (FFM): 51.9 kg (Should equal ATM + ECM. Rounding discrepancy of 0.1kg)
Hydration status: normal

Note: FM + FFM = 69.0kg = TM but this includes 1.5kg of clothing

DEXA Scan
Total Mass from scales: 70.3kg (clothed and with shoes)
Total Mass from DEXA (TM): 69.0 kg
Fat Mass (FM): 15.63 kg
Lean Mass (LM): 50.72 kg
Bone Mineral Content (BMC): 2.60 kg
Visceral Fat (VAT): 1.03 kg

So relative to DEXA the DF50 bio-impedance measurement has overestimated fat mass by 1.4 kg (9.4%). I strongly doubt that the cheaper household fat measuring scales can do better than this.

The visceral fat result is another interesting topic. But so as not to derail this particular thread discussion about protein I will make some comments about the visceral fat in a separate thread. http://forum.lowcarber.org/showthre...ewpost&t=475063

Thanks for the interesting info Bintang, sure it gives an idea upon the probably only modest accuracy of household fitness scales.
Maybe as GRB says the delta, that is the variation in successive weight may be used to our advantage, we don't know though the accuracy of the delta itself, that is the precision of the device.
I believe we can take a DEXA scan as a reasonable benchmark, it's strange enough that they did it clothed and with your shoes on!!!

The clothes and shoes were only on for the weight measurement on the scales prior to the scan. It doesn't need to be super accurate as it is just a guide for the operator. The DEXA scan calculates body mass independently of the scales.