If Excess Protein Turns into Fat...

On Mon, 27 Aug 2007, spodosaurus wrote:

> Ron Peterson wrote:
>> On Aug 26, 2:32 am, spodosaurus <spodosaurus@_yahoo_.com> wrote:
>>> Bill Penrose wrote:
>>>
>>>> No, the body can burn fat directly, but it needs some sugar to do
>>>> that. In other words, it can burn sugar only, and sugar plus fat, but
>>>> not fat only. The 'Atkins diet', where you limit sugars in the diet,
>>>> supposedly causes you to stop burning fat, too.
>>>
>>> Incorrect: glucose can be created from fats using the gluconeogenesis
>>> pathway and getting the energy for this pathway from the citric acid
>>> cycle that the catabolism of fat feeds into.
>>
>> Glucogenesis produces glucose from glycerol and proteins, not fatty
>> acids. Glycerol is only a small part of triglycerides.
>
> No, that is incorrect. Gluconeogenesis pathway produces glucose from
> pyruvate/oxaloacetate. Oxaloacetate can be taken right from the citric
> acid cycle, regardless of its source molecule (in this example, fatty
> acids).

But you can't make oxaloacetate from fat! Yes, carbons from fat flow into
the Krebs cycle, but to get them in, you need molecules of the
intermediates there already to accept them; to make oxaloacetate, you need
acetyl CoA and an existing molecule of oxaloacetate, so there's no *net*
synthesis - the number of molecules of the intermediates stays constant,
that's what makes it a cycle.

To make more of the intermediates, you need one of the anaplerotic
reactions (one of my favourite words, that!), and those start from sugars
and amino acids.

Although, having refreshed my memory of this, you *can* do anaplerosis
from fatty acids - but only if they're odd-length! And those are only made
by some bacteria, and only found in the human diet in significant
quantities in the meat of ruminants, which have those bacteria in their
guts. Even then, it's a small portion of the total fat, and you only get
one anaplerotic equivalent per fatty acid chain, so it's not going to get
you very far.

It's always been a puzzle to me why we don't have an enzyme capable of
making propionyl-CoA by methylating acetyl CoA, say using
methyl-tetrahydrofolate (although i'm kind of hazy on the ultimate source
of the methyl groups for that - might also need an acetyl-CoA
decarboxylase to make them ...). Or some kind of malonyl-CoA
isomerase-reductase complex. Or why we ever lost the glyoxylate cycle. We
could then use fat for everything, lose our dependence on sugars, and dump
all that ketone body junk. Oh well, more evidence for the absence of
intelligent design, i guess!

tom

--
Hier gaan over het tij, de wind, de maan en wij.

On Sat, 25 Aug 2007, Prisoner at War wrote:

> Then how come the body can't use stored fat when it needs protein? What,
> biochemically speaking, prevents it from turning fat back into protein
> the way it apparently turns fat back into sugar?

You've had plenty of other answers on this, but, basically (a) we can't
turn fat back into sugar and (b) both this inability and the inability to
turn fat into protein are because we lack a few crucial enzymes.

For protein, there's also a question of where you'd get the nitrogen from,
as amino acids contain nitrogen but fats don't. You'd need organic
nitrogen, which could come either from fixation of atmospheric nitrogen,
which means we'd need symbiotic nitrogen-fixing bacteria like plants (or a
whole new raft of genes of our own to do the job), or from proteins in the
diet - and then you're playing a trading game, because you could do things
like making two molecules of alanine (each of which contains one nitrogen
atom) from one of lysine (which contains two) and some carbon from fat,
you could never make two lysines starting from one.

> (I'm assuming that 'cause stored fat is used for energy, right? And the
> only form of energy for the body is sugar....)

No. Most of the energy you use comes from a set of reactions called the
Krebs cycle (aka the citric acid cycle and tricarboxylic acid cycle),
which burns something called acetyl coenzyme A (acetyl CoA). You can make
that from sugar or from fat. You can also turn it back into fat, but not
sugar. The process by which you make it from sugar is called glycolysis,
and that produces energy of its own as well; it can also be diverted away
from acetyl CoA to produce lactic acid. Glycolysis doesn't require oxygen,
but the Krebs cycle does, so that's what the body does when it needs
energy but doesn't have oxygen - you get less energy per molecule of
sugar, but it works. A consequence of this is that only sugar can fuel
anaerobic energy production, not fat. There is something called the Cori
cycle which uses energy to recycle lactic acid to sugar, but that's
another story!

I don't know if this makes things any clearer, but the separate steps are:

glucose -> pyruvate (glycolysis; makes some energy)
pyruvate -> lactic acid (used as an endpoint for anerobic metabolism)
pyruvate -> acetyl CoA + CO2 (first step in aerobic metabolism)
acetyl CoA + O2 -> CO2 + H2O (Krebs cycle; makes lots of energy)

The relationship between sugar and acetyl CoA is a bit like that between
wood and charcoal; you can make the latter from the former, and you can
burn both, but you can't make the former from the latter!

tom

--
Hier gaan over het tij, de wind, de maan en wij.

Tom Anderson wrote:
> On Mon, 27 Aug 2007, spodosaurus wrote:
>
>> Ron Peterson wrote:
>>> On Aug 26, 2:32 am, spodosaurus <spodosaurus@_yahoo_.com> wrote:
>>>> Bill Penrose wrote:
>>>>
>>>>> No, the body can burn fat directly, but it needs some sugar to do
>>>>> that. In other words, it can burn sugar only, and sugar plus fat,
>>>>> but not fat only. The 'Atkins diet', where you limit sugars in the
>>>>> diet, supposedly causes you to stop burning fat, too.
>>>>
>>>> Incorrect: glucose can be created from fats using the gluconeogenesis
>>>> pathway and getting the energy for this pathway from the citric acid
>>>> cycle that the catabolism of fat feeds into.
>>>
>>> Glucogenesis produces glucose from glycerol and proteins, not fatty
>>> acids. Glycerol is only a small part of triglycerides.
>>
>> No, that is incorrect. Gluconeogenesis pathway produces glucose from
>> pyruvate/oxaloacetate. Oxaloacetate can be taken right from the citric
>> acid cycle, regardless of its source molecule (in this example, fatty
>> acids).
>
> But you can't make oxaloacetate from fat! Yes, carbons from fat flow
> into the Krebs cycle, but to get them in, you need molecules of the
> intermediates there already to accept them; to make oxaloacetate, you
> need acetyl CoA and an existing molecule of oxaloacetate, so there's no
> *net* synthesis - the number of molecules of the intermediates stays
> constant, that's what makes it a cycle.
>

No human exists in a vacuum (literally, we tend to explode then freeze).
your hypothetical point here is not pertinent to the reality of the
situation - a person switching from carbohydrates to a protein+fat diet.
Acetyl CoA comes from fatty acid oxidation. You get C/2 acetyl-CoA's
from each fatty acid (C=number of carbons in the chain, and this is for
even number carbon chains). You originally said that humans can burn
sugar and fat, but that there must always be a carbohydrate source. This
is not correct, as topping up the intermediates can be done readily
through the protein consumed with the rest of the animal.

> Oh well, more evidence for the absence
> of intelligent design, i guess!

We marvel at the intricacies of what actually works and say 'something
intelligent must have designed this', and ignore the 85% junk and
half-assed bollocks that exists alongside

Ari


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In article <Pine.LNX.4.64.0708281521131.16561@urchin.earth.li >,
Tom Anderson <twic@urchin.earth.li> wrote:

> (a) we can't
> turn fat back into sugar

Fat can't be converted back (partially) into glucose? Since when?

Where does the glucose for the central nervous system come from for
those that do a lot of fasting?
--
Peace, Om

Remove _ to validate e-mails.

"My mother never saw the irony in calling me a Son of a bitch" -- Jack Nicholson

In article <Pine.LNX.4.64.0708281454130.16561@urchin.earth.li >,
Tom Anderson <twic@urchin.earth.li> wrote:

> On Mon, 27 Aug 2007, spodosaurus wrote:
>
> > Ron Peterson wrote:
> >> On Aug 26, 2:32 am, spodosaurus <spodosaurus@_yahoo_.com> wrote:
> >>> Bill Penrose wrote:
> >>>
> >>>> No, the body can burn fat directly, but it needs some sugar to do
> >>>> that. In other words, it can burn sugar only, and sugar plus fat, but
> >>>> not fat only. The 'Atkins diet', where you limit sugars in the diet,
> >>>> supposedly causes you to stop burning fat, too.
> >>>
> >>> Incorrect: glucose can be created from fats using the gluconeogenesis
> >>> pathway and getting the energy for this pathway from the citric acid
> >>> cycle that the catabolism of fat feeds into.
> >>
> >> Glucogenesis produces glucose from glycerol and proteins, not fatty
> >> acids. Glycerol is only a small part of triglycerides.
> >
> > No, that is incorrect. Gluconeogenesis pathway produces glucose from
> > pyruvate/oxaloacetate. Oxaloacetate can be taken right from the citric
> > acid cycle, regardless of its source molecule (in this example, fatty
> > acids).
>
> But you can't make oxaloacetate from fat! Yes, carbons from fat flow into
> the Krebs cycle, but to get them in, you need molecules of the
> intermediates there already to accept them; to make oxaloacetate, you need
> acetyl CoA and an existing molecule of oxaloacetate, so there's no *net*
> synthesis - the number of molecules of the intermediates stays constant,
> that's what makes it a cycle.
>
> To make more of the intermediates, you need one of the anaplerotic
> reactions (one of my favourite words, that!), and those start from sugars
> and amino acids.
>
> Although, having refreshed my memory of this, you *can* do anaplerosis
> from fatty acids - but only if they're odd-length! And those are only made
> by some bacteria, and only found in the human diet in significant
> quantities in the meat of ruminants, which have those bacteria in their
> guts. Even then, it's a small portion of the total fat, and you only get
> one anaplerotic equivalent per fatty acid chain, so it's not going to get
> you very far.
>
> It's always been a puzzle to me why we don't have an enzyme capable of
> making propionyl-CoA by methylating acetyl CoA, say using
> methyl-tetrahydrofolate (although i'm kind of hazy on the ultimate source
> of the methyl groups for that - might also need an acetyl-CoA
> decarboxylase to make them ...). Or some kind of malonyl-CoA
> isomerase-reductase complex. Or why we ever lost the glyoxylate cycle. We
> could then use fat for everything, lose our dependence on sugars, and dump
> all that ketone body junk. Oh well, more evidence for the absence of
> intelligent design, i guess!
>
> tom

I'll bet you have the Krebs cycle permanently memorized...

<sigh>

And the periodic table.
--
Peace, Om

Remove _ to validate e-mails.

"My mother never saw the irony in calling me a Son of a bitch" -- Jack Nicholson

On Tue, 28 Aug 2007, spodosaurus wrote:

> Tom Anderson wrote:
>> On Mon, 27 Aug 2007, spodosaurus wrote:
>>
>>> Ron Peterson wrote:
>>>> On Aug 26, 2:32 am, spodosaurus <spodosaurus@_yahoo_.com> wrote:
>>>>> Bill Penrose wrote:
>>>>>
>>>>>> No, the body can burn fat directly, but it needs some sugar to do that.
>>>>>> In other words, it can burn sugar only, and sugar plus fat, but not fat
>>>>>> only. The 'Atkins diet', where you limit sugars in the diet, supposedly
>>>>>> causes you to stop burning fat, too.
>>>>>
>>>>> Incorrect: glucose can be created from fats using the gluconeogenesis
>>>>> pathway and getting the energy for this pathway from the citric acid
>>>>> cycle that the catabolism of fat feeds into.
>>>>
>>>> Glucogenesis produces glucose from glycerol and proteins, not fatty
>>>> acids. Glycerol is only a small part of triglycerides.
>>>
>>> No, that is incorrect. Gluconeogenesis pathway produces glucose from
>>> pyruvate/oxaloacetate. Oxaloacetate can be taken right from the citric
>>> acid cycle, regardless of its source molecule (in this example, fatty
>>> acids).
>>
>> But you can't make oxaloacetate from fat! Yes, carbons from fat flow
>> into the Krebs cycle, but to get them in, you need molecules of the
>> intermediates there already to accept them; to make oxaloacetate, you
>> need acetyl CoA and an existing molecule of oxaloacetate, so there's no
>> *net* synthesis - the number of molecules of the intermediates stays
>> constant, that's what makes it a cycle.
>
> No human exists in a vacuum (literally, we tend to explode then freeze).

Actually, i believe that's a popular myth - you asphyxiate then freeze, no
exploding involved:

http://www.sff.net/people/Geoffrey.Landis/vacuum.html

> your hypothetical point here is not pertinent to the reality of the
> situation - a person switching from carbohydrates to a protein+fat diet.
> Acetyl CoA comes from fatty acid oxidation. You get C/2 acetyl-CoA's
> from each fatty acid (C=number of carbons in the chain, and this is for
> even number carbon chains). You originally said that humans can burn
> sugar and fat, but that there must always be a carbohydrate source.

That wasn't me.

> This is not correct, as topping up the intermediates can be done readily
> through the protein consumed with the rest of the animal.

Quite true. Sorry, i wasn't saying that you had to eat sugars to be able
to metabolise fat; i was just pointing out that you can't make sugar from
fat.

tom

--
People don't want nice. People want London. -- Al

On Tue, 28 Aug 2007, Omelet wrote:

> In article <Pine.LNX.4.64.0708281521131.16561@urchin.earth.li >,
> Tom Anderson <twic@urchin.earth.li> wrote:
>
>> (a) we can't turn fat back into sugar
>
> Fat can't be converted back (partially) into glucose? Since when?

Ooh, a few hundred million years, ish. I actually can't find out where in
our evolutionary lineage we lost it; somewhere after the vertebrates
separated out ~500 million years ago, but where exactly, i have no idea.

> Where does the glucose for the central nervous system come from for
> those that do a lot of fasting?

What glucose? Time to meet the metabolic substrate nobody mentions:

http://en.wikipedia.org/wiki/Ketone_bodies

There have been reports of glyoxylate enzyme activities in mammals, but
they're sporadic, and the consensus seems, to my outsider's eye, to be
that they haven't won acceptance. There's apparently no trace of genes for
the enzymes in the human genome, which kind of puts the kybosh on the
idea. But don't sue me if that's not so ...

And no, i haven't memorised the Krebs cycle, the periodic table, the
genetic code, or anything intellectual like that. I can probably tell you
the catalogue numbers of most of the antibodies i use, though!

tom

--
People don't want nice. People want London. -- Al

Tom Anderson <twic@urchin.earth.li> wrote:
> Omelet wrote:
>> Fat can't be converted back (partially) into glucose? Since when?
>
> Ooh, a few hundred million years, ish. I actually can't find out where in
> our evolutionary lineage we lost it; somewhere after the vertebrates
> separated out ~500 million years ago, but where exactly, i have no idea.

LOL

> There have been reports of glyoxylate enzyme activities in mammals,

Sightings of the beast... Here is one, http://pmid.us/2712349

> but they're sporadic, and the consensus seems, to my outsider's eye,
> to be that they haven't won acceptance. There's apparently no trace
> of genes for the enzymes in the human genome, which kind of puts the
> kybosh on the idea. But don't sue me if that's not so ...

Here is a good paper on this:
http://www.pubmedcentral.nih.gov/art...?artid=1630690

Of all animals only the roundworms are well documented to have the two
key enzymes (two in one). But those who found a rudimentary expression
in mammals etc. say that the enzymes are not coded by the homologous
genes (http://www.springerlink.com/content/g40v1765q46q8245/)

They mention those roundworms in support of the hypothesis, where the
stuff is already sufficiently diverged to became a single
bi-functional enzyme.

So, if rats drink plenty of vodka but otherwise starved but, a small
amount of fat can turn into carbs - http://pmid.us/8706872

This simply HAD to come from Russian scientists!

Wait a minute, in men too - http://pmid.us/12056879

In article <Pine.LNX.4.64.0708282349360.13899@urchin.earth.li >,
Tom Anderson <twic@urchin.earth.li> wrote:

> On Tue, 28 Aug 2007, Omelet wrote:
>
> > In article <Pine.LNX.4.64.0708281521131.16561@urchin.earth.li >,
> > Tom Anderson <twic@urchin.earth.li> wrote:
> >
> >> (a) we can't turn fat back into sugar
> >
> > Fat can't be converted back (partially) into glucose? Since when?
>
> Ooh, a few hundred million years, ish. I actually can't find out where in
> our evolutionary lineage we lost it; somewhere after the vertebrates
> separated out ~500 million years ago, but where exactly, i have no idea.

Ok, my bad.
My metabolic biochemistry is a bit rusty... (It's only been 21 years
since I took the classes, and it's been awhile since I've done any
serious reading on it).

So I did some googling last night at work and "studied". <G>

And of course, you are correct.
Thru various enzymatic pathways, fatty acids enter the oxidative
phosphorylation pathway directly and so do ketone bodies. They are then
converted to Acetyl CoA and from there to ATP, the final product
actually used for energy.

Cool.

Since a lot of ketone bodies are dumped in the urine, that is what makes
ketogenic dieting so much better. It's "Inefficient" so burns off more
fat. It still drives me nuts when I read things like "scientists don't
understand why people consuming the same number of protein and fat
calories burn off more body fat than people using low fat, high carb
diets".

It's like, duh.

>
> > Where does the glucose for the central nervous system come from for
> > those that do a lot of fasting?
>
> What glucose? Time to meet the metabolic substrate nobody mentions:
>
> http://en.wikipedia.org/wiki/Ketone_bodies

I saw LOTS of stuff on ketogenic diets being used to treat Epileptic
children. Interesting stuff.

>
> There have been reports of glyoxylate enzyme activities in mammals, but
> they're sporadic, and the consensus seems, to my outsider's eye, to be
> that they haven't won acceptance. There's apparently no trace of genes for
> the enzymes in the human genome, which kind of puts the kybosh on the
> idea. But don't sue me if that's not so ...

So I am presuming that base serum glucose levels are maintained via
Gluconeogenesis using protein if you are not consuming carbohydrates?
So if you eat insufficient protein, it's going to use your own muscles?

I've not googled far enough to find references for fasting metabolism.

>
> And no, i haven't memorised the Krebs cycle, the periodic table, the
> genetic code, or anything intellectual like that. I can probably tell you
> the catalogue numbers of most of the antibodies i use, though!
>
> tom

;-)

I had to memorize the damned thing three times in college and I STILL
don't remember all the steps!
--
Peace, Om

Remove _ to validate e-mails.

"My mother never saw the irony in calling me a Son of a bitch" -- Jack Nicholson

In article <27791@37722592.2843728293.14635.19392.17373>,
DZ <15980@1900132091.1700436.13514.2134.10068> wrote:

> Tom Anderson <twic@urchin.earth.li> wrote:
> > Omelet wrote:
> >> Fat can't be converted back (partially) into glucose? Since when?
> >
> > Ooh, a few hundred million years, ish. I actually can't find out where in
> > our evolutionary lineage we lost it; somewhere after the vertebrates
> > separated out ~500 million years ago, but where exactly, i have no idea.
>
> LOL
>
> > There have been reports of glyoxylate enzyme activities in mammals,
>
> Sightings of the beast... Here is one, http://pmid.us/2712349
>
> > but they're sporadic, and the consensus seems, to my outsider's eye,
> > to be that they haven't won acceptance. There's apparently no trace
> > of genes for the enzymes in the human genome, which kind of puts the
> > kybosh on the idea. But don't sue me if that's not so ...
>
> Here is a good paper on this:
> http://www.pubmedcentral.nih.gov/art...?artid=1630690
>
> Of all animals only the roundworms are well documented to have the two
> key enzymes (two in one). But those who found a rudimentary expression
> in mammals etc. say that the enzymes are not coded by the homologous
> genes (http://www.springerlink.com/content/g40v1765q46q8245/)
>
> They mention those roundworms in support of the hypothesis, where the
> stuff is already sufficiently diverged to became a single
> bi-functional enzyme.
>
> So, if rats drink plenty of vodka but otherwise starved but, a small
> amount of fat can turn into carbs - http://pmid.us/8706872
>
> This simply HAD to come from Russian scientists!
>
> Wait a minute, in men too - http://pmid.us/12056879

Nice links.

I needed more reading material. <G>
--
Peace, Om

Remove _ to validate e-mails.

"My mother never saw the irony in calling me a Son of a bitch" -- Jack Nicholson

On Tue, 28 Aug 2007, hanson wrote:

> What prevents or is missing in our metabolism that does not allow us to
> aminate (insert a NH2) into Leucine, (C6H13NO2) to yield Lysine
> (C6H14N2O2)? ... or to turn Valine C5H11NO2 by methyleneation (inserting
> a CH2) into the C6 amino acids? What is the reason for that in the
> thinking of the bio-med community? Which are the responsible genes or
> DNA markers? Are they known?

Yes, the genes are known. Our ancestors had them tens or hundreds of
millions of years ago, when they were rats or worms or jellyfish or
something. We've lost them since then. Why? I guess because we get enough
amino acids from our diet, and don't need to make them. Whether we lost
them by neutral drift (just because we didn't need them) or whether there
was some selective advantage to losing them, i'm not qualified to say.

tom

--
For me, thats just logic. OTOH, Spock went bananas several times using
logic. -- Pete, mfw

On Wed, 29 Aug 2007, DZ wrote:

> Tom Anderson <twic@urchin.earth.li> wrote:
>> Omelet wrote:
>>> Fat can't be converted back (partially) into glucose? Since when?
>>
>> but they're sporadic, and the consensus seems, to my outsider's eye, to
>> be that they haven't won acceptance. There's apparently no trace of
>> genes for the enzymes in the human genome, which kind of puts the
>> kybosh on the idea. But don't sue me if that's not so ...
>
> Here is a good paper on this:
> http://www.pubmedcentral.nih.gov/art...?artid=1630690
>
> Of all animals only the roundworms are well documented to have the two
> key enzymes (two in one). But those who found a rudimentary expression
> in mammals etc. say that the enzymes are not coded by the homologous
> genes (http://www.springerlink.com/content/g40v1765q46q8245/)

Aha. Those guys have actually purified this alleged enzyme, so it should
be child's play to sequence it and then go looking for the gene. I await
further reports with interest.

> So, if rats drink plenty of vodka but otherwise starved but, a small
> amount of fat can turn into carbs - http://pmid.us/8706872
>
> This simply HAD to come from Russian scientists!

I had the same thought when i saw those papers!

tom

--
For me, thats just logic. OTOH, Spock went bananas several times using
logic. -- Pete, mfw

On Aug 28, 1:12 am, Bill Penrose <penr...@iit.edu> wrote:
> On Aug 27, 7:26 pm, "hanson" <han...@quick.net> wrote:
>
> > Corpulent "Bill Penrose" <penr...@iit.edu> wrote in > [hanson]
> > Is it really that clean cut and simple?.. i.e. history shows that all the
> > members, save 2 guys, of the De Soto expedition died from protein
> > poisoning because they only ate their horses (like your rabbits)
> > but some Inuits live very happily by eating only fat, whale blubber.
>
> You can't get enough energy from lean meat. The body attempts to make
> energy by burning protein, and the nitrogen loading can poison or the
> body can simply starve.
>
> Blubber isn't just fat. There's protein there, too. I remember in my
> biochem classes in 1963-5 being told that Inuit have different
> metabolism that allows them to subsist without carbohydrates. Biochem
> was moderately primitive then, so I don't know what the modern story
> is. It is true that Inuit and white people eating the same high-fat,
> low-carbohydrate diets react differently, but I don't know the basis
> of it.

Presumably you refer to the fact that "white people" lose weight --
it's called the Atkin's diet. I've wonder what would happen if you
never stopped: would one reach stasis, or starve to death?

Another tidbit: I recall that wolves drink a great deal of water after
wolfing down that caribou, specifically to flush out the urea.

Tom Anderson <twic@urchin.earth.li> wrote:
> DZ wrote:
>> So, if rats drink plenty of vodka but otherwise starved, a small
>> amount of fat can turn into carbs - http://pmid.us/8706872
>>
>> This simply HAD to come from Russian scientists!
>
> I had the same thought when i saw those papers!

Russian scientists studying the glyoxylate shunt -
http://soldadoo.mylivepage.ru/image/61/455_yoga1.jpg
(I'm the guy with the larger biceps)

In article <1188404995.959960.96440@50g2000hsm.googlegroups.c om>,
Edward Green <spamspamspam3@netzero.com> wrote:

> On Aug 28, 1:12 am, Bill Penrose <penr...@iit.edu> wrote:
> > On Aug 27, 7:26 pm, "hanson" <han...@quick.net> wrote:
> >
> > > Corpulent "Bill Penrose" <penr...@iit.edu> wrote in > [hanson]
> > > Is it really that clean cut and simple?.. i.e. history shows that all the
> > > members, save 2 guys, of the De Soto expedition died from protein
> > > poisoning because they only ate their horses (like your rabbits)
> > > but some Inuits live very happily by eating only fat, whale blubber.
> >
> > You can't get enough energy from lean meat. The body attempts to make
> > energy by burning protein, and the nitrogen loading can poison or the
> > body can simply starve.
> >
> > Blubber isn't just fat. There's protein there, too. I remember in my
> > biochem classes in 1963-5 being told that Inuit have different
> > metabolism that allows them to subsist without carbohydrates. Biochem
> > was moderately primitive then, so I don't know what the modern story
> > is. It is true that Inuit and white people eating the same high-fat,
> > low-carbohydrate diets react differently, but I don't know the basis
> > of it.
>
> Presumably you refer to the fact that "white people" lose weight --
> it's called the Atkin's diet. I've wonder what would happen if you
> never stopped: would one reach stasis, or starve to death?
>
> Another tidbit: I recall that wolves drink a great deal of water after
> wolfing down that caribou, specifically to flush out the urea.

Or maybe it's because they are thirsty?
--
Peace, Om

Remove _ to validate e-mails.

"My mother never saw the irony in calling me a Son of a bitch" -- Jack Nicholson

On Wed, 29 Aug 2007, Omelet wrote:

> In article <Pine.LNX.4.64.0708282349360.13899@urchin.earth.li >,
> Tom Anderson <twic@urchin.earth.li> wrote:
>
>> On Tue, 28 Aug 2007, Omelet wrote:
>>
>>> In article <Pine.LNX.4.64.0708281521131.16561@urchin.earth.li >,
>>> Tom Anderson <twic@urchin.earth.li> wrote:
>>>
>>>> (a) we can't turn fat back into sugar
>
> So I am presuming that base serum glucose levels are maintained via
> Gluconeogenesis using protein if you are not consuming carbohydrates? So
> if you eat insufficient protein, it's going to use your own muscles?

That's certainly what i was taught. We spent weeks on this in my second
year at university, and i remember that the switch from fed to fasting
metabolism is very complicated, but that i eventually understood it. But
that's all i remember .

>> And no, i haven't memorised the Krebs cycle, the periodic table, the
>> genetic code, or anything intellectual like that. I can probably tell
>> you the catalogue numbers of most of the antibodies i use, though!
>
> ;-)
>
> I had to memorize the damned thing three times in college and I STILL
> don't remember all the steps!

Citrate to ... mevalonate to ... phosphoenolpyruvate to ... halfpastate to
.... nothanksijustate ... er ... CO2! Still got the old magic!

tom

--
File under 'directionless space novelty ultimately ruined by poor
self-editing'

On Wed, 29 Aug 2007, DZ wrote:

> Tom Anderson <twic@urchin.earth.li> wrote:
>> DZ wrote:
>>
>>> So, if rats drink plenty of vodka but otherwise starved, a small
>>> amount of fat can turn into carbs - http://pmid.us/8706872
>>>
>>> This simply HAD to come from Russian scientists!
>>
>> I had the same thought when i saw those papers!
>
> Russian scientists studying the glyoxylate shunt -
> http://soldadoo.mylivepage.ru/image/61/455_yoga1.jpg (I'm the guy with
> the larger biceps)

We recently carried out similar work here:

http://s223.photobucket.com/albums/d...ent=bucket.jpg

I'm the guy with the bucket .

tom

--
File under 'directionless space novelty ultimately ruined by poor
self-editing'

In article <Pine.LNX.4.64.0708300039320.31832@urchin.earth.li >,
Tom Anderson <twic@urchin.earth.li> wrote:

> On Wed, 29 Aug 2007, Omelet wrote:
>
> > In article <Pine.LNX.4.64.0708282349360.13899@urchin.earth.li >,
> > Tom Anderson <twic@urchin.earth.li> wrote:
> >
> >> On Tue, 28 Aug 2007, Omelet wrote:
> >>
> >>> In article <Pine.LNX.4.64.0708281521131.16561@urchin.earth.li >,
> >>> Tom Anderson <twic@urchin.earth.li> wrote:
> >>>
> >>>> (a) we can't turn fat back into sugar
> >
> > So I am presuming that base serum glucose levels are maintained via
> > Gluconeogenesis using protein if you are not consuming carbohydrates? So
> > if you eat insufficient protein, it's going to use your own muscles?
>
> That's certainly what i was taught. We spent weeks on this in my second
> year at university, and i remember that the switch from fed to fasting
> metabolism is very complicated, but that i eventually understood it. But
> that's all i remember .

Hence PSMF'ing is mucho better than actual fasting.
A' La' Lyle... You get to keep your muscle. Mostly anyway.

>
> >> And no, i haven't memorised the Krebs cycle, the periodic table, the
> >> genetic code, or anything intellectual like that. I can probably tell
> >> you the catalogue numbers of most of the antibodies i use, though!
> >
> > ;-)
> >
> > I had to memorize the damned thing three times in college and I STILL
> > don't remember all the steps!
>
> Citrate to ... mevalonate to ... phosphoenolpyruvate to ... halfpastate to
> ... nothanksijustate ... er ... CO2! Still got the old magic!
>
> tom

Heh!

All I remember is (Name Carbon based molecule here) goes in, ATP, CO2
and H20 come out. <g>
I think it's 4 ATP's per Carbon? <shrugs>

Oh, and it takes place in the Mitochondria. Y'know, those symbionts in
your cells that put you in touch with "The Force".

Oh, nevermind, those were "Midichlorians" (or however the hell George
Lucas spelled it).

;-)
--
Peace, Om

Remove _ to validate e-mails.

"My mother never saw the irony in calling me a Son of a bitch" -- Jack Nicholson

In article <Pine.LNX.4.64.0708300043140.31832@urchin.earth.li >,
Tom Anderson <twic@urchin.earth.li> wrote:

> > Russian scientists studying the glyoxylate shunt -
> > http://soldadoo.mylivepage.ru/image/61/455_yoga1.jpg (I'm the guy with
> > the larger biceps)
>
> We recently carried out similar work here:
>
> http://s223.photobucket.com/albums/d...current=bucket
> .jpg
>
> I'm the guy with the bucket .
>
> tom
>
> --
> File under 'directionless space novelty ultimately ruined by poor
> self-editing'

I've seen a LOT worse "drunk" picks floating around the web. ;-)
--
Peace, Om

Remove _ to validate e-mails.

"My mother never saw the irony in calling me a Son of a bitch" -- Jack Nicholson

Omelet <omp_ome...@gmail.com> wrote:
>
> So I am presuming that base serum glucose levels are maintained via
> Gluconeogenesis using protein if you are not consuming carbohydrates?
> So if you eat insufficient protein, it's going to use your own muscles?

That's one of at least two sources of blood glucose when low
carbing, eating a successfull predator diet or fasting. The other
is fat metabolism.

Glucogenesis from protein is 50ish% efficient by calorie.

Fat gets cut into fatty acids and glycerol. The fatty acids into
acetyl-CoA and ketones. Two glycerols get bonded to one
glucose. The energy yield of glucode from fat is 10ish% by
calorie.

So whether you're burning your own muscles depends on
how much non-muscle lean has been stored (very little I suspect),
how much dietary protein in excess of metabolic amino acid
needs, and how much fat is being burned.

High fat diets are more lean sparing than high protein diets
per assorted studies - especially the "fat fast" one that is one
of the triggers for Dr Atkins to design his low carb diet. Why
isn't directly obvious - Doesn't extra fat at 10% take so much
more to maintain blood sugar levels? I figure this has a lot to
do with why ketotic diets have a "metabolic edge", though. It
takes excess ketone generation to achieve enough blood sugar.
The problem with that line of reasoning are two facts. 1) The
"metabolic edge" drops as the amount of excess body fat
drops and it hits zero somewhere around 20 pounds left to
lose and this doesn't match the mechanism to keep blood
sugars up. 2) Levels of ketosis (really ketonuria) start out
high in the first couple weeks of a ketotic diet then drop and
this also doesn't match the mechanism to keep blood sugars up.

"Doug Freyburger" < Levels of ketosis (really ketonuria) start out high in
the first couple weeks of a ketotic diet then drop and this also doesn't
match the mechanism to keep blood sugars up.>

Basically every diet loses its body-shock effect after 2-3 weeks and the
spectacular losses that often accompany the first 2-3 weeks are gone to just
a pound or two after that.

I have often wondered if one way around it would be to keep switching diets
every three weeks?

In article <XfKBi.50955$Lu.15947@bignews8.bellsouth.net>,
"Wally West" <wallywest@curb.com> wrote:

> "Doug Freyburger" < Levels of ketosis (really ketonuria) start out high in
> the first couple weeks of a ketotic diet then drop and this also doesn't
> match the mechanism to keep blood sugars up.>
>
> Basically every diet loses its body-shock effect after 2-3 weeks and the
> spectacular losses that often accompany the first 2-3 weeks are gone to just
> a pound or two after that.
>
> I have often wondered if one way around it would be to keep switching diets
> every three weeks?

Yes.

I've found I can maintain better ketosis if I go ahead and have some
carbs every couple of weeks.

That very thing is designed into Lyle's PSMF diet.

I've done fat fasting and can lose about 1/2 lb. per day doing it.
Atkins recommended that you not do it for more than 5 days (iirc, I've
not read his books in awhile) as it's nutritionally deficient. I did it
for 2 weeks one time and lost 10 lbs before going for some protein and
veggies.

It's hard as hell to stay on that thing tho' as you are always hungry.
1,000 calories of fat is not a lot of food.

Part of that weight loss tho' is muscle glycogen depletion which is why
when you DO indulge in carbs after strict low carbing, you will see a
sudden weight gain (usually about 5 lbs. in my case) due to water being
pulled into muscles along with the glycogen storage.

This is why carb depletion is done prior to a contest then you "carb up"
the day before the actual competition. The increase in fluid retention
inside of the muscle body is often overdone giving you some increased
muscle hardness for the stage.
--
Peace, Om

Remove _ to validate e-mails.

"My mother never saw the irony in calling me a Son of a bitch" -- Jack Nicholson

In article <1188507334.167097.24410@z24g2000prh.googlegroups. com>,
Doug Freyburger <dfreybur@yahoo.com> wrote:

> Omelet <omp_ome...@gmail.com> wrote:
> >
> > So I am presuming that base serum glucose levels are maintained via
> > Gluconeogenesis using protein if you are not consuming carbohydrates?
> > So if you eat insufficient protein, it's going to use your own muscles?
>
> That's one of at least two sources of blood glucose when low
> carbing, eating a successfull predator diet or fasting. The other
> is fat metabolism.

I thought it was said that fat would not convert back to glucose?
Now I'm confoozed. <G>

>
> Glucogenesis from protein is 50ish% efficient by calorie.

Hence the concept of "metabolic advantage" with low carb diets that some
scientists don't seem to understand.

>
> Fat gets cut into fatty acids and glycerol. The fatty acids into
> acetyl-CoA and ketones. Two glycerols get bonded to one
> glucose. The energy yield of glucose from fat is 10ish% by
> calorie.

<fixed the word "glucode" <G>>

Body fat or dietary fat?

I presume you mean dietary fat.

Hence the accelerated weight loss I experience with "fat fasting".

Too bad that diet is such a bitch. It'd be a panacea.

>
> So whether you're burning your own muscles depends on
> how much non-muscle lean has been stored (very little I suspect),
> how much dietary protein in excess of metabolic amino acid
> needs, and how much fat is being burned.

And how great your glycogen storage capacity.

>
> High fat diets are more lean sparing than high protein diets
> per assorted studies - especially the "fat fast" one that is one
> of the triggers for Dr Atkins to design his low carb diet.

See my previous post.

> Why
> isn't directly obvious - Doesn't extra fat at 10% take so much
> more to maintain blood sugar levels?

Due to the supposed caloric content, it fascinates me that one can lose
weight faster using pure fat than pure protein, or a mix of both.
Fat = 9 calories per gram
Protein = 4 calories per gram

Yet, you really will see a drastic difference in loss of body weight
consuming 1,000 calories of fat per day (with very limited "other"
calorie sources) than eating 1,000 calories worth of protein per day.

It's fascinating.

The length of time you can keep it up tho' is very limited and you have
to wonder what the drawbacks can be. Body fat loss vs. lean muscle loss
with a deficit of amino acids for instance.

All other things being equal of course using vitamin supplements.

> I figure this has a lot to
> do with why ketotic diets have a "metabolic edge", though.

That is due to it's sheer inefficiency compared to the body metabolizing
carbs.

> It
> takes excess ketone generation to achieve enough blood sugar.
> The problem with that line of reasoning are two facts. 1) The
> "metabolic edge" drops as the amount of excess body fat
> drops and it hits zero somewhere around 20 pounds left to
> lose and this doesn't match the mechanism to keep blood
> sugars up. 2) Levels of ketosis (really ketonuria) start out
> high in the first couple weeks of a ketotic diet then drop and
> this also doesn't match the mechanism to keep blood sugars up.

I know that from experience. Unfortunately.

Want some fun? Google for "rabbit starvation".
--
Peace, Om

Remove _ to validate e-mails.

"My mother never saw the irony in calling me a Son of a bitch" -- Jack Nicholson

On Fri, 31 Aug 2007, Omelet wrote:

> In article <1188507334.167097.24410@z24g2000prh.googlegroups. com>,
> Doug Freyburger <dfreybur@yahoo.com> wrote:
>
>> Omelet <omp_ome...@gmail.com> wrote:
>>
>>> So I am presuming that base serum glucose levels are maintained via
>>> Gluconeogenesis using protein if you are not consuming carbohydrates?
>>> So if you eat insufficient protein, it's going to use your own
>>> muscles?
>>
>> That's one of at least two sources of blood glucose when low carbing,
>> eating a successfull predator diet or fasting. The other is fat
>> metabolism.
>
> I thought it was said that fat would not convert back to glucose? Now
> I'm confoozed. <G>

Fat *mostly* doesn't convert back into glucose. I may have skimped on
exegesis here.

What it comes down to is that one molecule of fat is made of one molecule
of glycerol bonded to three molecules of fatty acid. The glycerol has
three carbon atoms, and the fatty acids 16-20ish each, so the fatty acids
make up ~95% of the fat molecule; when talking about fat, we tend to
forget about the glycerol and just treat it as a bunch of fatty acids.

Anyway, fatty acids can't be made into glucose, only burned or made into
ketone bodies, but glycerol can. However, it's a rather small amount - you
need two glycerols to make a glucose, so you get half a glycerol per
molecule of fat, which also gives you three molecules of fatty acid, worth
8-10 turns of the Krebs cycle each.

>> Glucogenesis from protein is 50ish% efficient by calorie.
>
> Hence the concept of "metabolic advantage" with low carb diets that some
> scientists don't seem to understand.

Yebbut you don't use the protein to make glucose, you break it down
straight to acetyl CoA and burn it. It's still less efficient than fat,
but better than 50%, i think.

I think this metabolic efficiency stuff is a red herring. It's not like
you, or your body, eats a specific number of calories of whatever food and
then stops, and protein's better for you because less of those calories
become available; you eat as much as it takes to stop you being hungry, so
if protein was less good at stopping you being hungry, you'd eat more of
it, and end up with more calories in your blood.

Rather, the amount you eat is decided by your body's nutrient-sensing
machinery. High-protein/fat diets make you satiated using less calories
than high-carb diets because, AIUI, the machinery is geared to detecting
protein and fat as indicators of food intake. That's the secret - if you
eat rich food, you eat less of it than if you eat wholesome food. There's
no metabolic magic going on, just some sleight of hypothalamus!

>> Fat gets cut into fatty acids and glycerol. The fatty acids into
>> acetyl-CoA and ketones. Two glycerols get bonded to one glucose.

Dammit, that's what i just said, only a quarter the length. CURSE YOU,
FREYBURGER!

>> The energy yield of glucose from fat is 10ish% by calorie.
>
> <fixed the word "glucode" <G>>
>
> Body fat or dietary fat?
>
> I presume you mean dietary fat.

Either.

>> So whether you're burning your own muscles depends on how much
>> non-muscle lean has been stored (very little I suspect),

What would constitute non-muscle lean? Glycogen, i guess, but that goes
early; protein in other tissues? You know, i have no idea how the body
uses, or regulates its use of, protein in various different tissues for
energy while fasting. I'd guess (well, hope), that it takes the skeletal
muscles down to a bare minimum before it starts burning the organs, and
that it then starts with the liver and spleen before things like heart,
lungs and brain!

>> how much dietary protein in excess of metabolic amino acid needs, and
>> how much fat is being burned.
>
> And how great your glycogen storage capacity.

I doubt it's big enough in anyone to make a difference in a diet lasting a
week or more.

>> High fat diets are more lean sparing than high protein diets per
>> assorted studies - especially the "fat fast" one that is one of the
>> triggers for Dr Atkins to design his low carb diet.
>
> See my previous post.
>
>> Why isn't directly obvious - Doesn't extra fat at 10% take so much more
>> to maintain blood sugar levels?

Is this true when the diets are isocaloric? If so, it's very surprising; i
would have thought protein would generate a stronger protein-preserving
anabolic stimulus than fat.

Mind you, there is some evidence that fat consumption promotes protein
synthesis - someone posted a paper a while back showing that drinking
whole milk led to more muscle protein synthesis than an isocaloric dose of
whey protein. They showed it wasn't down to insulin levels, too; it sort
of suggests there's either a direct effect of blood FFA on protein
synthesis in muscle, or that there's an as yet unknown anabolic hormone
that's produced in response to fat consumption.

> Want some fun? Google for "rabbit starvation".

Sounds like a hoot.

tom

--
10 PARTY : GOTO 10

On Thu, 30 Aug 2007, Omelet wrote:

> In article <XfKBi.50955$Lu.15947@bignews8.bellsouth.net>,
> "Wally West" <wallywest@curb.com> wrote:
>
>> "Doug Freyburger" < Levels of ketosis (really ketonuria) start out high
>> in the first couple weeks of a ketotic diet then drop and this also
>> doesn't match the mechanism to keep blood sugars up.>
>>
>> Basically every diet loses its body-shock effect after 2-3 weeks and
>> the spectacular losses that often accompany the first 2-3 weeks are
>> gone to just a pound or two after that.
>>
>> I have often wondered if one way around it would be to keep switching
>> diets every three weeks?
>
> That very thing is designed into Lyle's PSMF diet.
>
> I've done fat fasting and can lose about 1/2 lb. per day doing it. [...]
> It's hard as hell to stay on that thing tho' as you are always hungry.
> 1,000 calories of fat is not a lot of food.

What sort of vegetables can you eat on PSMF? Whenever i've tried to lose
weight, filling up on green veg has always been helpful. The best thing is
oriental broths made with leafy veg, stock and/or soy sauce and chillies:
basically, a bowl of hot water and celluose, contaminated with salt,
glutamic acid and capsaicin!

I keep typing PMSF instead of PSMF - something quite different, but which
also protects protein:

http://www.sigmaaldrich.com/catalog/...il/SIGMA/P7626

tom

--
10 PARTY : GOTO 10

In article <Pine.LNX.4.64.0708311822330.30238@urchin.earth.li >,
Tom Anderson <twic@urchin.earth.li> wrote:

> > That very thing is designed into Lyle's PSMF diet.
> >
> > I've done fat fasting and can lose about 1/2 lb. per day doing it. [...]
> > It's hard as hell to stay on that thing tho' as you are always hungry.
> > 1,000 calories of fat is not a lot of food.
>
> What sort of vegetables can you eat on PSMF?

Mostly green ones with leafy greens being the best.
You know, those "negative calorie" high fiber ones. ;-)

Lettuce, cabbage, endive, broccoli, spinach, chard, celery, to name a
few of my personal favorites.

> Whenever i've tried to lose
> weight, filling up on green veg has always been helpful.

Yes.

> The best thing is
> oriental broths made with leafy veg, stock and/or soy sauce and chillies:
> basically, a bowl of hot water and celluose, contaminated with salt,
> glutamic acid and capsaicin!

Try tossing in some Bok Choy and/or chinese cabbage.
Mushrooms work too. Chitin is not digestible by the human organism, and
they are high in trace minerals.

>
> I keep typing PMSF instead of PSMF - something quite different, but which
> also protects protein:
>
> http://www.sigmaaldrich.com/catalog/...il/SIGMA/P7626
>
> tom

Cool.

Theoretically, so does Clenbuterol, but it's not legal. ;-)
--
Peace, Om

Remove _ to validate e-mails.

"My mother never saw the irony in calling me a Son of a bitch" -- Jack Nicholson

Tom Anderson <twic@urchin.earth.li> wrote:
>> Doug Freyburger <dfreybur@yahoo.com> wrote:
> What it comes down to is that one molecule of fat is made of one
> molecule of glycerol bonded to three molecules of fatty acid.
>
>>> Two glycerols get bonded to one glucose.
>
> Dammit, that's what i just said, only a quarter the length. CURSE YOU,
> FREYBURGER!

I blame those damn foreigners for sp