Shine <shineraju@gmail.com> wrote:
Yes but ... there's many "buts". Here's some explanation.
* The brain cannot survive entirely without glucose.
* You might get faint, and even pass out, and might
get the right first-aid.
from:
Post-exercise ketosis, ketone bodies
Johan H Koeslag , Medical Physiology,University of Stellenbosch
at http://academic.sun.ac.za/medphys/ketosis.htm
WHAT IS KETOSIS?
"Ketosis" is the name given to any situation where "ketone bodies"
accumulate in the blood, and are then partly breathed out, some
appears in the urine, but the majority are burnt by the muscles, brain
and other tissues of the body. The name "ketone bodies" is a bit
confusing. The name is a corruption of "ketones of the body". So they
are not bacteria, nor little particles or organisms, or anything that
might have a "body". They are just substances that are formed from the
metabolism of fats. They are "acetoacetic acid", and "3-hydroxybutyric
acid", and common or garden "acetone".
These substances are produced by the liver whenever the liver has to
produce glucose at a very high rate.
BACKGROUND METABOLISM
We store relatively little carbohydrate, most of it being turned into
fat immediately after a meal. So, about 60% of what we normally eat is
starch and sugars, but as soon as it is absorbed from the gut, this
carbohydrate rapidly removed from the blood, some of it being turned
into glycogen in the liver and in muscles, but the majority is turned
into fats by the liver and fat cells. Between meals this fat is then
released from the fat cells and is our primary fuel for everyday use,
as well as for exercise etc. The amount of glycogen stored, after a
hearty meal, will be used up within 24 hours if no new meal is taken.
This just emphasises how little carbohydrate we are capable of
storing.
Once all the liver glycogen is used up (after 24 hours of fasting, or
much sooner if you exercise) the liver has to make glucose from
non-carbohydrate sources. The process is called "gluconeogenesis". The
liver can make glucose from lactic acid, if available, but its prime
raw ingredient is protein. Fats cannot be turned back into glucose.
As a result of an intriguing metabolic quirk (See: Footnote), whenever
the liver engages in "gluconeogenesis" it burns fats (to provide the
energy for the gluconeogenic process), but is unable to combust them
(the fats) right down to carbon dioxide and water. The half broken
down products of fat metabolism in the liver are then converted into
these "ketone bodies". They are released into the blood, from where
they are taken up by any tissue that wants them.
In fact, they are lapped up (voraciously devoured) in preference to
glucose or fats or lactic acid by most tissues, where they are burnt to
carbon dioxide and water. The heart loves them, so do the muscles, and,
most importantly, the brain which normally only burns glucose (it cannot
use fats - again for some strange metabolic quirk) also loves them and
will burn them in preference to glucose, although the brain cannot
survive entirely without glucose.
IMPORTANCE OF KETONE BODIES
Thus, ketone bodies play a very important role in being able to
survive a shortage of food, especially carbohydrates. If it were not
for ketone bodies most of us would be unconscious after 48 hrs of
fasting!
POST-EXERCISE KETOSIS
Whenever carbohydrates are in short supply, during fasting, a low
carbohydrate diet, or after exercise (or a combination of these!) the
liver will produce ketone bodies (plus glucose, via gluconeogenesis,
of course). The ketone bodies have a distinctive smell, which can be
detected in the breath. The urine will also smell of them (if the
other urine smells don't overwhelm them). The smell is difficult to
describe. Some people cannot smell acetoacetic acid as such, but can
recognise the acetone smell in the breath. If you are able to smell
acetoacetic acid it is very distinctive, and not easily mistaken for
anything else. The closest other smell resembling that of acetoacetic
acid is very ripe apples, but not everyone finds that a useful
description.
Ketone bodies disappear very rapidly from the blood if you eat
carbohydrates. Eat a couple of hearty slices of bread (with jam), a
Chelsea bun, or a generous slice of cake, and they are gone from the
blood within minutes. If you do not eat anything, or if you
deliberately avoid carbohydrates then the ketone body concentrations
in the blood increase steadily for several hours, and can remain
elevated in the blood (and breath etc) for days.
IN SUMMARY
So, if you smell ketone bodies in your breath after exercise, then all
it means is that you are not eating enough carbohydrate. That in
itself is not a disaster. It is a perfectly normal reaction to an
emergency situation, and one that has helped humanity survive
shortages of food for many years at a time. I have no idea how it
influences a person's ability to exercise: my guess is that
performance would not be as good as it would be on a more generous
carbohydrate diet. I don't think it affects people intellectually or
emotionally, other than that it is often associated with hunger or a
craving for carbohydrate (chocolates etc), and might thus make people
crabbier than they might otherwise be.
POSSIBLE DANGERS
There is a small but real possibility, if you are regularly
experiencing post- exercise ketosis, that your liver just cannot make
enough glucose for your needs. (Remember that ketone bodies are
produced as a consequence of the gluconeogenic process. See:
Footnote.) When I was inducing post-exercise ketosis in the subjects
for my research (healthy young students), a few of them would start to
feel faint, sweaty and very unsteady on their feet about 6 hours after
the exercise (they were allowed no food intake during those 6 hours).
Their ketone bodies levels in the blood would then be sky high; but
what was making them feel faint and dizzy were the low levels of
glucose in the blood. Their livers were just not coping with the
demand for glucose (despite just sitting around doing nothing - except
watching videos - for those 6 hours after exercise). The treatment was
simple: we just gave them a plateful of cake and muffins with lots of
jam to eat. Within minutes the symptoms were gone, and when we tested
the blood, ketone bodies could no longer be found, and their blood
sugars would be normal.
A more serious situation could arise if the low blood sugar develops
while you are out running. Apart from the dangers of falling into the
traffic, there is the further danger that people would not
automatically think of giving you cake to eat while you are lying in
the road in a semi-conscious, or confused state!
DO NOT DRINK ALCOHOL IF YOU ARE KETOTIC!
Alcohol is a powerful inhibitor of gluconeogenesis. In fact, it forces
part of the gluconeogenic metabolic process into reverse. This means
that if all the glucose in the blood is being derived from
gluconeogenesis then the consumption of alcohol will inevitably cause
the blood glucose level to fall. Worse still, the alcohol also stops
ketone body production, thus leaving the brain entirely without fuel.
A person who is ketotic is 100% reliant on gluconeogenesis to maintain
adequate levels of glucose in the blood. If, under these circumstances
alcohol is taken, the person will become disorientated and might lose
consciousness, not just from the alcohol, but from low blood sugar.
Needless to say, this could be very dangerous, and even fatal.
Dawid Michalczyk <dm@eonworks.com> wrote:
Yes. Even in a less hazardous version, the idea of the OP
would result in a weight loss of water and muscle:
from a layman's site: Patri's Journal: exPatriation,
http://patrifriedman.com/writing/jou...75ketosis.html
Ketosis without caloric restriction [not what the OP
outlined, BTW]
Ketones are acidic and mildly poisonous. Two major ketones
are acetoacetic acid and beta-hydroxybutyric acid, which are
strong organic acids. Excreting them causes the loss of
sodium and potassium. The way acetoacetic acid is broken
down (spontaneous decarboxylation) produces acetone - not a
nice thing to have in your bloodstream. Acetone accumulates
in plasma and is slowly disposed of by respiration
(reference).
You would be losing K and Na after you've depleted them
already, a bad idea.
Bad things about ketosis:
Fasting decreases immune function (this study suggests that the
first study applies to atkins-induced ketosis).
Low-carb is better than no-carb ("Although some workers use VLCD
consisting only of protein, the author prefers those also
containing carbohydrate because they prevent excessive ketosis,
hyperuricemia, diuresis, electrolyte loss, re-feeding oedema, and
may improve muscular endurance").
A comment she includes:
"Cox and Knutsen also are skeptical about the metabolic mechanism,
ketosis, that initiates the rapid weight loss. Ketosis results from
the incomplete metabolism of fatty acids. It comes on when the body is
deprived of carbohydrates, its preferred fuel source, and turns to its
own fat and the fat in food for fuel. The body assembles the
fatty-acid fragments into substances called ketones. These are
poisonous to the system, and the body flushes them out in the urine
with water, according to the Tufts University Health and Nutrition
Letter. So the initial rapid weight loss on the Atkins diet is mostly
water.
"The body must also break down its own muscle tissue to provide the
brain and red blood cells with glucose, a required nutrient," Cox
says. "Muscle tissue holds water, and when lost, results in a
significant amount of weight loss."
