CATEGORY: biology/metabolism
TECHNICAL: ****
SUMMARY:
This document gives the rather technical/intimate
details of how someone who is low-carb and ketogenic can
sustain a weightlifting session and have the energy to do so
start through finish.
It's a pretty rough read for those uninterested in
the biomedicine, so I'll give you the short version here.
Your body accomplishes this task by using the "waste products"
of active muscle exercise: lactate (which gives you that
burning feeling) and pyruvate (another precursor to the
glucose generation process) to synthesize new glucose in the
liver. This new sugar is then sent back into the bloodstream
for use by the active muscle.
It's important to realize that amino acids are part
of this process, so be sure to get enough protein in your
diet as well as fats, or you may risk muscle loss (to the
conversion process).
Incidentally, you will also notice (as I have) that
because of this glucose generation process - if you check for
excess ketones in the urine stream (with ketostix) right after
you train - you'll see that you're temporarily non-ketogenic.
That is why it is a good idea to follow up a weight
lifting session with a little easy, short aerobic work. Cycling,
for example, can more rapidly remove the excess lactate from
the working muscle and convert it back to muscle/liver glycogen.
This not only reduces your post-workout soreness, but
also drops your blood sugar and speeds you back into a ketogenic
state. (and primes your muscles with stored glycogen for the
next lifting session)

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Subject: The anabolic diet...
Date: Sun, 4 Jun 1995 13:22:37 -0500 (CDT)

Hello!

I finally found the answer I was looking for regarding the anabolic
diet. When people (my adv. nutrition teacher, biochemistry professor
etc.) put me on the spot, I have reluctantly explained the diet based
upon the manuals findings, which I explained were not technical enough,
and had real difficulty convincing them. But now I finally found an
answer that is technical enough, and explains the reasoning behind this
ever so commonly asked question; "since weight training is anaerobic,
where is your energy going to come from when you don't consume enough
carbs, since glycolysis is the major pathway involved in anaerobic
exercise?". Well I finally struck pay dirt. It took an inordinate
amount of time, too much time in fact, and I am going to call Optimum
Training Systems and request that they revise the manual or add an
addendum in which this is explained more in depth. Like I said, you are
going to be hard pressed when someone in the know starts battering away
with technical questions, that the diet doesn't provide. Sure the manual
tells you that dietary and body fat will be the fuel for your workouts
along with the creatine from the red meat, but that doesn't cut it. Which
finally leads me to this answer.

Since anaerobic wt. training HAS to go through glycolysis, I thought
that readdressing that pathway might lead me to an answer, and it did. As
you know the 2 hormones insulin and glucagon work together, when carbs
are present, insulin secretion from the pancreas increases, and times
when carbs are low, glucagon secretion increases to supply carbs for
energy. When going through glycolysis there are 3 regulatory steps, one
of them involves the enzyme PFK-1 (phospofructokinase-1). It is one of
the reactions that are catalyzed early in glycolysis, the third step If I
recall correctly. Anyway, it seems that this enzyme PFK-1 is sensitive
to levels of carbs in the blood. When carbs are low, as in the diet,
glucagon is going to be chronically activated, which in turn will
influence the enzyme PFK-1. When this happens, it tells the metabolic
pathway that glucose just is not available, and therefore the reaction of
glycolysis can not proceed in the normal fashion. THat is why it is a
regulatory step. When this happens, glycolysis basically skips all the
normal steps and proceeds to the end where pyruvate is formed. From
there pyruvate can be converted (broken down) to lactate. Once lactate
is formed from a reaction catalyzed be lactate dehydrogenase, lactate has
no other metabolic fate than reconversion to pyruvate. Hence, lactate is
commonly considered a metabolic dead end. Since lactate formation
catalyzed by lactate dehydrogenase regenerates NAD+ from NADH, the
pathway of glycolysis is complete, with NAD+ becoming available for
glyceraldehyde 3 phosphate dehydrogenase reaction. Thus no net oxidation
or reduction takes place during anaerobic glycolysis to lactate. The
final product, lactate in glycolysis generates 2 mol ATP per mol of
glucose consumed. Oxygen is not required in either case. In most cells,
the majority of ATP is produced by oxidative phosphorylation, which is
strictly an oxygen dependent process. Yet, in the cornea of the eye, for
example, oxygen availability is limited by poor blood circulation.
Anaerobic glycolysis meets the need for ATP in the abscence of sufficient
oxygen for oxidative phosphorylation. When skeletal muscle is active,
lactate and pyruvate are transported out of the muscle cells and carried
via the circulatory system to the liver where lactate is converted to
pyruvate by the action of hepatic lactate dehydrognease. Pyruvate can be
further metabolized in various ways by the liver: a fraction of it is
aerobically oxidized to Co2 via the Krebs cycle (citric acid cycle), and
some of it is transaminated to alanine, which is used in protein
synthesis. Pyruvate in liver cells can also be converted back to free
glucose by gluconeogenesis. Liver is the principal organ responsible for
regulating the supply of blood glucose to other cells of the body,
including skeletal muscle cells. Thus, a portion of the metabolic burden
of muscular contraction is borne by the liver, which metabolizes the
by-products of muscle activity (lactate and pyruvate) and synthesizes
blood glucose. This inter-organ metabolism, in which liver receives
lactate and pyruvate and furnishes glucose for skeletal muscle, where
glucose is glycolytically metabolized to generate ATP, is referred to as
the Cori Cycle.

Hope this reaches all the doubters out there who were not convinced
the first time! Thanks!

Jeffrey P. Krabbe
Pre-Dietetics, Senior
University of Nebraska, Lincoln

:cool: TJ :cool: