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Fenbay
06-05-2003, 04:08 PM
Subject says it all. Is there a mechanism for the body to turn protein into fat? And if not....if you ate 5000 calories in pure protein and only burned 2500 calories where would it go? And would you be breaking the law of thermodynamics if it didnt get stored.

Ok maybe the subject didn't say it all.

raniali
06-05-2003, 04:10 PM
the body turns excess carbohydrates into fat. it can well turn excess protein into the same storage material. the wonders of the human body.

if it didn't get stored it's most likely because it wasn't fully digested and, therefore, passed thru the gut.

bradley
06-05-2003, 05:11 PM
Originally posted by Fenbay
Subject says it all. Is there a mechanism for the body to turn protein into fat?

Yes the pathway does exist but it is not very effecient. One exception to this would be if your diet had less than 10% of total calories coming from fat.



And if not....if you ate 5000 calories in pure protein and only burned 2500 calories where would it go? And would you be breaking the law of thermodynamics if it didnt get stored.


Some of the calories would be lost in the digesting of the protein (thermic effect of food), some would be converted to glucose and some would probably be converted to fat seeing as how that is a large amount of protein. Unless you are taking in an extremely high amount of protein then you don't really have to worry about excess protein converting to fat. If you overfed with a grossly high amount of protein you would see some fat through the de novo lipogenesis pathway.

The body would use the protein in some way. You can't get away from calories in calories out.:)

bradley
06-05-2003, 05:15 PM
Originally posted by raniali
if it didn't get stored it's most likely because it wasn't fully digested and, therefore, passed thru the gut.

I believe the absorption rate of protein by the body is something like 90-95%. Unless the individual has some sort of digestive problem then I don't think any significant amount of protein would just pass throught the gut.

Backdraft
06-05-2003, 09:18 PM
Don't forget that 5000 calories of pure protein is 1250 grams. At that level protein has to be toxic.

bradley
06-06-2003, 03:11 AM
Originally posted by Backdraft
Don't forget that 5000 calories of pure protein is 1250 grams. At that level protein has to be toxic.

Yes, I would imagine that you would have hyperammonia/hyperurea problems with that amount of protein.

Although I would think that ancient man would have eaten a large amount of protein but not anywhere near that amount. I have seen it suggested that their protein intake was around 3g per kg of bw.

Fenbay
06-06-2003, 07:04 AM
Good stuff, the 5k calorie was just an arbitrary number I threw out. I had once heard the body can not store protein as fat which didn't make sense since the body can obviously catabolize protein in the form of muscle tissue for glycogen.

Since this process is not very efficient does the body avoid it all together if sufficient fat/carbs are coming in?

bradley
06-06-2003, 08:07 AM
Originally posted by Fenbay
Since this process is not very efficient does the body avoid it all together if sufficient fat/carbs are coming in?

Well if you are taking in enough carbs and EFAs then the body will not necessarily convert the protein to fat, but if you eat enough of it the calories will have to go somewhere (used for energy, converted to glucose, etc.). Therefore if you were to eat a large enough amount of calories you would not necessarily store the excess protein as fat, but you would end up storing the excess dietary fat as fat and you would also eliminate the need for bf to be used as energy (no fat burning).

raniali
06-06-2003, 11:19 AM
Originally posted by bradley


I believe the absorption rate of protein by the body is something like 90-95%. Unless the individual has some sort of digestive problem then I don't think any significant amount of protein would just pass throught the gut.

brad - absorption rates vary depending on the source of protein with whey protein being the best absorbed followed by eggs .... however, according to the following link, you are lucky to get above 80% absorption.

http://www.columbu.com/nutrition/protein.html

from another site:
In one study, 16 healthy nonathletes of lean to moderate build, average age 24, were fed either whey or casein to determine the absorption rate of amino acids from the two proteins. Shortly after eating whey, subjects had a brief 68% increase in protein synthesis; some amino acids were oxidized for energy and no reduction in protein breakdown was noted. Casein caused a more moderate increase in protein synthesis (31%), but fewer of its amino acids were oxidized for energy and whole-body protein breakdown was reduced by 34%. Casein led to greater overall protein uptake than whey did.

not all proteins are created equal.

Holto
06-06-2003, 01:24 PM
I think he meant once in teh small intestine

bradley
06-06-2003, 02:09 PM
Originally posted by raniali


brad - absorption rates vary depending on the source of protein with whey protein being the best absorbed followed by eggs .... however, according to the following link, you are lucky to get above 80% absorption.


I am not disputing that fact, those sites are describing the net protein utilization which is defined here: http://www.wikipedia.org/wiki/Net_protein_utilization
This is a measure that defines the essential amino acid and also identifies the limiting amino acids. Naturally things like vegetable proteins will be much lower on the NPU chart because they are missing many key amino acids.

This is different than what I was referring to. If you eat 100 calories of chicken then that will yield approximately 90-95 calories and you are not going to lose calories just by excreting unused protein. All of the protein might not be utilized by the body because of the limiting amino acids but you will still be taking in 95 cals.

http://groups.google.com/groups?q=protein+excess+author:Lyle+McDonald&hl=en&lr=&ie=UTF-8&selm=3EC28CA2.E53140D9%40grandecomIMRETARDED.net&rnum=3

I agree with you in that all proteins are not created equal. I hope all this rambling makes sense:)

bradley
06-06-2003, 02:13 PM
I think this site defines NPU much better than the first link.

http://nbaf.com/nbaf/ap6pe.htm

restless
06-06-2003, 02:16 PM
Bradley is correct, our bodies have a very efficient protein absorption rate, the only diference is the speed at which this occurs and how close to optimal the amino acid profile is.

body
06-07-2003, 05:06 AM
all the macronutrients of fat, prot and carbs are asborbed at roughly 90-99%.

fat has the highest level generally with carbs bieng the lowest in healthy people.


the answer to your question is yes, but not the most efficient thing your body does.

As i have not got a text book next to me. I can't remeber what the pathway is called. but its one of those long words.

bradley
06-07-2003, 02:30 PM
Originally posted by body
As i have not got a text book next to me. I can't remeber what the pathway is called. but its one of those long words.

I know that de novo lipogenesis is usually in reference to the conversion of carbs to fat but this would also be the pathway that excess protein is converted to fat. I am not really 100% sure but I believe this is correct.