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Researched
and Composed by
Jacob Wilson, BSc. (Hons), MSc. CSCS
Address correspondence to:
jwilson@abcbodybuilding.com
Layman’s Journal of
HYPERPLASIA Research 1(4):
Published August 31, 2006
Related Articles
The
following faq / summary of leucine research is based on the papers listed below
Wilson, J. (2006) Leucine’s General Effects on Muscle Growth and Protein
Balance.
Wilson,
J. (2006) Leucine’s Effects and Interaction with Insulin and Muscle Growth
Wilson,
J. (2006) The interaction between Leucine and Exercise on Muscle Growth
Wilson, J. (2006) The role of leucine and Anabolic Resistance
Wilson,
J. (2006) The Effects of leucine and fat metabolism
For an
in depth and referenced discussion on leucine, refer to those papers. Click
Here to access
them. The following paper is meant to summarize key points and practical
applications, in a mildly technical manner.
Introduction
The
branched chain amino acids, leucine, isoleucine, and valine are three of the
essential amino acids which have the perfect capability for acting as signaling
molecules to control muscle growth. This is because the liver lacks the enzyme
responsible for initiating their breakdown. Therefore, while a large amount of
the other amino acids are degraded and taken up by the liver and other tissues
of the gut, the BCAAs enter into peripheral circulation, where skeletal muscle
tissue is relatively unscathed.
It has
been known for some time that consuming a complete meal stimulates protein
synthesis. The components of a meal have now been analyzed in depth by the
research. This research has revealed that amino acids are responsible for 80 %
of the protein synthesis which occurs after feeding. It also reveals that out
of all the amino acids only one is able to stimulate protein synthesis by itselfà
The BCAA leucine. Leucine also has several other functions including regulating
the hormone insulin, controlling protein breakdown rates, stabilizing blood
glucose levels, along with a host of other functions. The following paper will
be formatted in a questions and answers format in order to address these
particular roles.
How does leucine effect
protein synthesis?
Protein
synthesis refers to the process of constructing new proteins. It is
accomplished by first copying instructions from DNA onto an mRNA molecule
(transcription). Following the mRNA is taken into the cells interior and
attached to complex machinery known as the Ribosome, and its accompanying
ribosomal proteins. Once attached a new protein is constructed, and this
process is known as translation.
Protein synthesis can change rapidly during exercise, after feeding, and during
fasting conditions such as when you sleep at night. The evidence is clear that
these rapid changes occur at the beginning stages of translation, known as
translation initiation.
Translation is controlled by a family of proteins known as initiation factors.
For example they are responsible for binding mRNA to a ribosome (e.g. attaching
the instructions for building a protein to the machinery responsible for
building the protein). Increased leucine concentration leads to an increase in
the formation of these initiation factors. Leucine also activates a protein
known as ribosomal protein S6 (S6), which actually stimulates production of more
initiation factors and other ribosomal proteins. In other words S6 increases
the capacity of a cell to produce proteins.
Leucine
does not directly stimulate any of these processes. Instead increased
concentrations of leucine activate a molecule known as Mammalian target of
rapamycin (mTOR). This cellular machine ends out activating the initiation
factors and increasing a cells capacity to increase protein synthesis.
The amazing thing is that mTOR is sensitive to leucine concentration, growth
factors released from exercise, energy status in the cell, and insulin
concentrations. Therefore for protein synthesis to act optimally it requires an
interaction between all of these factors.
In
summary increased leucine concentration activates mTOR, which activates protein
synthesis, and increases a cells capacity to produce new proteins.
Summary: Leucine
à
mTOR à
Protein Synthesis
à
Skeletal Muscular Growth
What is Leucine’s Role
in regulating protein degradation (breakdown)?
Leucine’s primary role appears to be increasing protein synthesis. But recall
that muscle growth is the difference between protein synthesis and breakdown
(degradation). Leucine appears to decrease protein breakdown. For example
leucine has lowered markers of muscle damage in both resistance training and
endurance conditions. There are a number of theories as to why this occurs.
In a recent paper my colleague Gabriel Wilson and I submitted for publication,
we discussed the possibility that because leucine is the precursor to HMB, that
its conversion to HMB may explain some of leucines effects on protein
breakdown. For those not familiar with HMB, this is a metabolite of leucine
which is mainly known as an inhibitor of protein breakdown. It has been
demonstrated to decrease muscle loss in both exercise and clinical conditions.
The only problem is that only 2-10 % of leucine is converted to HMB. Yet, if
you analyze a bodybuilder’s diet, which frequently consists of 200 to 300 grams
a day of protein, it is conceivable that this is how it is eliciting some of its
effects. This would amount to 20 to 30 grams of leucine. If the average of 5 %
were converted then this would give a range of 1 to 1.5 grams of HMN, and if the
maximum were converted it would give a range of 2-3 grams of HMB daily. If an
individual is supplementing with EAAs rich in leucine the numbers can increase.
A second theory is that leucine can directly decrease pathways which initiate
the breakdown of tissues. There is a great deal of evidence for this as well.
In
summary leucine probably acts through both indirect (HMB) and direct mechanisms.
I should also bring up another point. Muscle tissue is made of 80 % BCAAs, and
these are preferentially broken down ( in terms of amino acids) during
exercise. Thus, by supplying an outside source of BCAAs such as leucine, you
can spare your own muscular stores. The same applies to dieting conditions
How do Diets Rich in
Leucine Stimulate Net Positive Protein Balance?
As
stated protein balance must be positive for muscle growth to occur. Protein
Balance is summarized by the following equation:
Protein
balance = Protein synthesis – Protein degradation
During
the course of a day human beings constantly cycle from positive to negative
protein balances, and these correspond to post food consumption and fasting
conditions. Post food consumption periods last 2-3 hours after a meal when
nutrients and amino acids are rich in the blood stream. If an individual has
consumed a leucine rich meal, then they can maximally stimulate protein
synthesis during this time frame. Once nutrients lower to fasting levels,
individuals enter into a state of net protein breakdown.
For this reason bodybuilders first approach to maintaining a positive protein
balance is to consume a leucine rich meal every two to three hours, thereby
avoiding catabolic states.
Muscle growth however is a small process when viewed from a day to day basis,
and on average most people neither gain nor loose muscle tissue in a single
day. This is summed by an excellent quote by by Combaret and colleagues (2005):
“Skeletal muscle protein synthesis decreases in the
postabsorptive (PA) state and increases in the postprandial (PP) state, while
protein breakdown follows the inverse pattern. In adults, net positive
protein balance in the PP state and net negative protein balance in the PA state
cancel each other.
They
conclude on exactly how this cancellation process occurs:
“In humans protein mass
increases in daytime and decreases overnight so that muscle protein mass does
not change throughout the day and night cycle.
In
article one I argued that the night time sleep cycle is one of the most critical
keys to muscle growth in a bodybuilder’s arsenal. There are two steps to
fighting turning what amounts to a potentially catabolic period to an amazing
period of growth.
The first step is by consuming a slow digesting protein source prior to bed
time. However this will only last at best the first half of sleep. The typical
bodybuilder is in a state of net protein breakdown for at least 4 hours a
night. If you add that up over 365 days this accumulates to approximately 1500
hours or a 60 full days of time! Therefore you can experience 60 days worth of
muscle tissue loss a year or replace that with 60 days worth of muscle tissue
gain.
I will
discuss the pre bed and mid sleep meals briefly.
How much leucine should
an individual consume in a given day?
The
problem here is that protein requirements are hardly established, especially for
athletes. For example if you look at the RDA for leucine, you roughly need 2-4
grams a day of it. But this is based on leucine’s function as a building block
for proteins. The situation is much more complex then this, because leucine has
many other metabolic roles. In fact in non exercising individuals leucines
metabolic use has been calculated to be up to 12 grams daily. Yet, it appears
that its function as a regulator of protein synthesis, and breakdown are
proportional to its levels in the diet.
It’s important to understand that leucine is about 10 % of high quality
proteins. Thus if we only analyze leucine’s role in protein synthesis, we see
that the standard gram per pound of bodyweight of protein for a bodybuilder
amounts to at least 20 grams of leucine per day. We have also provided evidence
that protein needs may be higher than this. I highly suggest reading article
one’s section on dietary reference intakes to fully understand the situation.
In summary however, leucine intake per day for athletes may be optimized at
20-30 grams a day, but in reality it is the timing, and pattern of leucine
ingestion that is critical.
What is the role of other Essential Amino
Acids in Stimulating Protein Synthesis?
If you
administer leucine alone, protein synthesis rises for only 30 minutes, but if
you provide other essential amino acids then protein synthesis remains elevated
for at least 2 hours. Thus, they play a supporting role. Also leucine
administered alone can lower the concentration of other amino acids, particular
other BCAAs. This is because leucine stimulates the enzyme which degrades all
BCAAs. If given in the absence of other BCAAs, they will lower in
concentration, and protein synthesis will lower with their decrease.
How much leucine is
optimal in a single setting?
Protein
synthesis appears to be fully restored at around 2.5 grams, but can most likely
be maximized at 3 to 4 grams per serving. If calculating based on bodyweight,
the highest amount would be 0.048 grams of leucine per kg of bodyweight per
serving.
Assuming that most high quality proteins such as whey and meats are
approximately 10 % leucine then roughly 30 to 40 grams of protein will meet the
3-4 gram leucine standard in a single setting, which is roughly 150 to 220
calories. If consuming an essential amino acid supplement such as the Essential
Amino Acid shooter, one serving administers 3 grams of leucine at 45 calories
per serving.
What should I consume in
my Pre Bed Time Meal?
Before
bedtime an individual will want to maximize protein synthesis, while minimizing
protein degradation. Casein appears to only slowly increase protein synthesis,
but markedly enhances protein degradation. It also contains approximately 9 %
leucine content. One cup of cottage cheese will deliver approximately 28 grams
of protein, if it is low fat, and 2.5 grams of leucine. Protein synthesis may
be able to be increased with a higher leucine content. In fact, evidence
suggests that increasing whey protein from 22 grams to 33 grams increased
protein synthesis. Whey is higher in leucine and so the participants in this
study went from 2.2 to 3.3 grams of leucine.
In
casein the leucine is delivered very slowly into circulation, which is most
likely why protein synthesis is not increased to a great extent, as compared to
whey protein which rapidly and drastically increases protein synthesis.
Remember, it is the extracellular increases in leucine which stimulate protein
synthesis. Therefore a slow release will only expose cells to a moderate levels
of leucine and so not cause maximal protein synthesis. Casein stays in the gut
for quite some time. The main reason is because it contains opioid peptides
which slow gastric emptying rate and motility. Therefore in the case of
consuming casein, I recommend the upper upper range of leucine intake which
amounts to about 0.048 grams of leucine per kg of bodyweight. For a 200 pound
man this amounts to about 4.4 grams of leucine.
What an
individual can do pre bed is to consume more than a cup of cottage cheese so as
to get more leucine, or consume a high leucine containing product along with the
casein. I would opt for the latter. One scoop of the amino acid shooter
contains 1 gram of leucine and is only 15 calories. In contrast you would have
to consume over 100 calories more of cottage cheese to match that amount.
Because of the opioid peptides released, the leucine from the shooter, even
though it is rapidly digested on its own, should be slowly released if consumed
as a chaser to the cottage cheese. The hope here is to optimally stimulate
protein synthesis and degradation.
To avoid
storing fat a fibrous green vegetable should be consumed such as broccoli, which
itself is antiestrogenic, and so should assist athletes in not holding water and
attaining a more tight appearance.
At this
time I also recommend consuming essential fatty acids in the form of fish oil
pills rich in EPA and DHA. EPA has been demonstrated in muscle wasting
conditions such as starvation to actually hinder muscle loss!
Glutamine also is critical in this meal. Glutamine makes up over 60 % of
intramuscular amino acids. It is also the preferred amino acid for
gluconeogenesis during fasting conditions such as sleep, or when carbohydrates
are low such as before bedtime. Therefore administration of glutamine can serve
a number of functions.
1. If the intracellular and extracellular pools of glutamine levels are low, the
intracellular pool will be depleted, causing muscle tissue to be broken down to
replace these losses
2. Glutamine draws water into the cell and hydrates it, which may improve
protein balance.
3. Glutamine can actually be used to increase glycogen synthesis in muscle
tissue in the absence of insulin, and because it is a very gluconeogenic amino
acid it can assist the liver in maintaining stable glucose levels throughout the
night.
Also
note that before bed you can consume other slow digesting proteins such as
steak.
What should I consume during my Mid
Sleep Meal?
I advice
setting the alarm in mid sleep, and having a shake next to your bed. I
typically mix a mixture of EAAs for caloric efficiency, with a protein powder.
To slow digestion I consume EPA in the form of fish oil pills. Further, I
include HMB to further hinder protein degradation, as well as glutamine. Shoot
for at least 3 grams of leucine here.
If you want to slightly slow digestion, but keep calories low, have EAAs, and
consume only a small amount of cottage cheese, such as a fourth cup. The opioid
peptides in it should slow gastric emptying.
Sample
Pre and MidSleep Meal
Pre Bed
1 cup cottage cheese
1 to 2 scoops of amino acid shooter
fish oil pills amounting to at least a 1 to 1.5 grams of EPA
1 gram of HMB
5-10 grams of glutamine
Mid Sleep
10 grams of essential amino acids, containing at least 3 grams of leucine to
restore protein synthesis
¼ cup casein
1 to 1.5 grams of EPA
1 gram of HMB
5-10 grams of glutamine
Does leucine ‘alone’ stimulate insulin
secretion and is this how it exerts its effects on protein synthesis?
Studies are conflicting as
some have found no increase in insulin when leucine is administered alone,
while others have. To clarify Dr. Anthony and colleagues measured insulin
levels immediately after leucine administration and found that it increased
insulin from 15-45 minutes. Thus it appears that it does increase insulin
transiently and that measuring insulin after this time frame will not yield
significant increases.
In order to investigate if insulin modulates leucine’s effects, scientists will
either block the action of insulin, or block insulin release. When this occurs
leucine’s effects on protein synthesis are partly but not fully hindered.
Recall that leucine increases S6, which is the ribosomal protein responsible for
increasing the capacity of a cell to conduct protein synthesis. This is
completely blocked when insulin is hindered. Leucine also enhances the
initiation of translation (the initiation stage of protein synthesis) and this
is only partly blocked when insulin is hindered. Thus, leucine has both insulin
dependent and insulin independent effects on protein synthesis.
How much insulin is
needed in order for leucine’s effects on protein synthesis to be maximized?
Leucine
can maximally stimulate protein synthesis at fasting levels of insulin, and
perhaps at slightly lower levels than this! Therefore spiking insulin levels
for the purpose of enhancing leucines effects on protein synthesis do not appear
to be necessary. Currently scientists are divided. Either insulin plays a
supportive or passive role in supporting leucines effects on protein synthesis,
or a direct role. Either way this is maximized at low levels.
Can insulin stimulate
protein synthesis independent of leucine and other amino acids?
Insulin
administered alone does not appear to have an effect on protein synthesis. The
rationale is that insulin increases uptake of amino acids and therefore lowers
their concentration in the blood when given alone. Extracellular amino acid
levels are critical for protein synthesis to occur. However, when amino acid
levels are maintained insulin may be able to stimulate protein synthesis when it
is at extremely high levels. This is confirmed in studies which administer
either insulin alone, or carbohydrates alone. No protein synthesis is
stimulated and the individual remains in a muscle wasting condition. In
contrast when amino acid levels are maintained protein synthesis is stimulated
when insulin is raised to very high levels.
However,
insulin potently decreases protein breakdown, independently of amino acids. In
fact it is considered the main player in decreasing protein breakdown, but
individuals remain in negative protein balance without aminos.
Can insulin and leucine work together in a synergistic fashion to increase
muscle growth?
Like leucine, insulin appears
to elicit its actions on protein synthesis through an mTOR dependent mechanism,
as well as mTOR independent mechanisms. When leucine and insulin are combined
their effects on increasing a cell’s capacity for protein synthesis are
synergistic. This means that if insulin increases the capacity of a cell to
increase protein synthesis 2 fold, and so does leucine, combined their effects
are greater than 4 fold.
The current rationale is that insulin actually increases blood flow to muscle
tissue, which if combined with increasing levels of amino acids (particularly
leucine ) would increase amino acid concentrations and delivery to muscle
tissue, thereby amplifying their effects.
Insulin increases blood flow + increased leucine
à
greater concentration of leucine surrounding muscle tissue
à amplified effects on protein synthesis.
It is also
important to note that as stated, leucine alone either does not or only
transiently increases plasma insulin levels. Yet, when combined with insulin,
it actually notably increases plasma insulin levels. The rationale is that
insulin is cleared primarily through degradation (e.g. it is broken down like
other proteins). Because leucine has anticatabolic effects, it may decrease
insulin clearance levels.
Can you discuss more of
the effects of insulin on protein breakdown?
Yes,
White
leucine is the primary regulator of protein synthesis, insulin is the primary
regulator of protein breakdown in that it decreases it by hindering pathways
responsible for protein breakdown.
In an intriguing study participants were given one of three drinks after
exercise. The first was a glucose drink, the second combined whey protein with
glucose, while the third added leucine to the glucose / whey serving. Results
indicated that protein balance was negative in the first condition, became
positive in the glucose / whey condition, and increased again when leucine was
added.
Here’s the interesting fact. Protein balance appeared to increase with
increasing insulin levels. Finally they analyzed the relationship (correlation)
between leucine and protein synthesis and insulin and protein synthesis. They
found that leucine was positively related to protein synthesis (as leucine
increases protein synthesis does as well), while insulin was not significantly
correlated. However, insulin was inversely correlated to protein breakdown,
meaning when insulin levels rise, protein breakdown decreases.
For practical applications on how to manipulate carbohydrates for insulin
release see the following papers
http://www.abcbodybuilding.com/laywindowsemi.php
http://www.abcbodybuilding.com/laywindownon.php
Both exercise and
leucine stimulate protein synthesis. Is there any time differences between the
two?
Yes,
leucine in a mixture of EAAs stimulates protein synthesis for 2-3 hours, where
as exercise stimulates protein synthesis for up to 72 hours. The take home
message is that you need amino acids with a high frequency.
The
second take home message is that even though protein synthesis is elevated with
exercise for 72 hours, these effects lower with time. In our publication on
Contemporary issues in protein consumption we provided the following graph to
demonstrate this
Figure
1.0. The response of protein synthesis to exercise. Adapted from
Wilson and Wilson (2006).
This is one of the reasons why HIT training may not be as effective as a higher
frequency of training, which is able to maintain higher levels of protein
synthesis throughout a 7 day period, then a once a week program, which has
diminishing effects.
Both resistance training
and cardio are forms of exercise. Why does exercise trigger protein synthesis,
while endurance exercise can decrease it?
First lets give a brief
overview of the different responses to exercise.
1. Resistance training does not change protein synthesis much during the
exercise session, but causes it to raise up to 72 hours after. However, if you
do not consume amino acids, protein breakdown exceeds synthesis, and overall you
lose muscle tissue. This means that you will be in a net catabolic state unless
amino acids are supplied immediately following training.
2. Endurance exercise lowers protein synthesis during and after exercise.
Combined with increased protein degradation, this can be a recipe for disaster!
Now to answer the question!
The difference between the two appears to be related to blood concentrations of
leucine. Leucine levels do not lower during resistance exercise, while they
lower in endurance exercise. The lowering of plasma leucine levels is
correlated with lowered protein synthesis. As further evidence, when leucine is
administered after endurance exercise, protein synthesis is fully restored.
Why is the maintenance of leucine levels so
important to maintaining protein synthesis?
While the answer is extremely
complex, it can be simplified as follows.
1. Recall that mTOR is the machinery that leucine acts on to trigger protein
synthesis.
2. It appears that leucine, insulin, and growth factors such as insulin like
growth factor increase the activity of mTOR.
3. But, decreased energy stores in the cell, such as occurs during exercise,
decreases the activity of mTOR.
When leucine levels are maintained they are able to counter the negative effects
of lowered energy stores. But, the combination of lowered leucine, and
decreased energy stores in the cell leads to a net decrease in protein
synthesis.
Can
supplementation inhibit the catabolic effects of cardio?
This question is critical and applies mainly to two situations.
1. Long duration cardio
2. Cardio on an empty stomach, particularly after an overnight fast.
Both are avoided because they are catabolic. But why are they catabolic?
Evidence suggests that they may be so due to lowered plasma leucine levels.
Thus, supplementing with an essential amino acid mixture prior to endurance
exercise that is long duration, or cardio in the morning may negate the
catabolic effects seen.
More studies need to be done to examine this, but the implications are great for
two reaons
1. Long duration cardio relies on a greater percentage of fat
2. cardio on an empty stomach relies on a greater percentage of fat then cardio
closer to a previous meal.
Aging appears to be linked to losses of muscle
tissue, and a failure to be able to gain muscle tissue in a number of
circumstances. Why is this the case, and is their a point to the elderly
bodybuilding?
One of the more frequent
questions I receive to my email account and in person is “can I still gain
muscle at this age?” Typically my answer is that the evidence supports the
efficacy at bodybuilding at any age.
First,
the question discusses the link between aging and muscle loss. Statisticallly
speaking, after the age of 50 the average loss of muscle tissue is 0.5-2 % per
year!
The question however is what is causing this, because if we know then we can
reverse these effects. Fortunately science has shed a great deal of light on
the matter.
First we need to understand that losses in muscle tissue are again related to
overall protein balance. At some point in a 24 hour time period, either protein
synthesis or degradation are lower or higher respectively in the elderly than
the young.
When measuring normal fasting levels of protein balance, differences between the
young and elderly appear negligible. However after a meal is consumed, the
young respond with an increase in protein synthesis and a decrease in protein
degradation, while in many cases the elderly do not. This suggests signaling
deficits to anabolic stimuli, and we think they are related to leucine.
In one study the young and elderly were given 7 grams of EAAs which were 27 %
leucine. Only the young responded with enhanced protein balance. Then the
experimenters upped the percentage of leucine to 47 %, and found that the
anabolic response to the EAAs was restored to youth levels in the elderly!
Thus, the amount of leucine ingested is critical for the elderly.
So how can the elderly up their leucine intake? It seems that at levels of 15
grams of essential amino acids no differences are found between the young and
elderly in response to feeding. This is because at this dose, the amount of
leucine is high enough to saturate protein synthetic machinery. So, the
suggestion is that the elderly should consume 15 to 20 grams of EAAs, or 30-40
grams of high quality protein per meal. Interestingly enough, evidence suggests
that the elderly may benefit from faster digesting proteins. The reason may be
related to the fact that faster digesting proteins can raise extracellular
leucine levels high enough to elicit enough of an increase in plasma leucine
levels to maximally activate the protein synthetic machinery in the elderly.
Overall
the take home message is that the elderly can benefit greatly from bodybuilding,
as long as they are consuming large doses of leucine per meal.
What are the overall differences
between higher protein or higher carbohydrate diets on body composition?
The typical RDA type recommendations, suggest that individuals only need 50-100
grams of protein per day. Or expressed in the ratio of carbohydrates to
proteins, the recommendations by the American Health Association (AHA) are 3.5
grams of carbs for every 1 gram of protein. In contrast, when calories are held
constant and protein intake is increased to the typical bodybuilding diet which
allows for 1 gram per pound of bodyweight or higher the ratio of carbs to
protein lowers. Typically studies look at higher protein diets as a ratio of
1.5 grams of carbs per 1 gram of protein.
Evidence
suggests that the higher carb diet causes difficulties in controlling blood
glucose levels, causes elevated and sustained increases in insulin levels, which
leads to decreased use of fat for fuel. Higher insulin levels also drastically
lower glucose levels, which leads to greater levels of hunger.
In contrast when protein intake is such that the ratio of carbohydrates to
protein is lowered to 1.5, evidence suggests greater fat loss, maintenance of
lean tissue mass , higher satiety , lower post absorptive insulin levels. Here
is a summary of what occurs between groups
Comparing fat loss
For
example in a 16 week study by Dr. Layman and colleagues, individuals lost nearly
twice the fat (19.4 vs 12.3 pounds) on the higher protein diet, then the higher
carbohydrate diet, even though calories were exactly the same (both induced a
500 calorie deficit)! Conversely the loss of muscle tissue was three times
greater in the high carbohydrate group than the high protein group!
This
suggests that calories are only one factor involved in fat loss diets, while the
ratio of carbs to proteins is another absolutely critical variable, which can
have drastic effects on fat loss.
Comparing Plasma Glucose levels
Individuals who consume the higher protein diet have more stable blood glucose
levels after an overnight fast, and 2 hours after a meal. Those on higher
carbohydrate diets are more likely to have low blood glucose levels, which is
not only negative in terms of satiety, performance, and mental fatigue, but
causes plasma triglyceride levels to rise. Elevated plasma triglyceride levels
actually causes insulin resistance!
Plasma Insulin Response
After feeding insulin and glucose levels rise. At about 2 hours following a
meal, plasma glucose levels return to normal basal levels, but insulin remains
elevated. Remember, insulin is a hypoglycemic hormone. This means that it
lowers glucose levels. So, the higher insulin is at the two hour mark, the
lower blood glucose levels will be.
Studies show that the higher carbohydrate condition has lower glucose levels and
higher plasma glucose levels as compared to the high protein condition.
So how do high protein diets increase
fat loss, and spare muscle tissue?
1. Higher protein diets increase satiety. This is most likely related to the
fact that higher protein diets maintain a more stable blood glucose level. When
plasma glucose levels lower we become hungry. Higher satiety reduces feeding
behavior which is counter to fat loss.
2. Higher protein diets stimulate the use of a greater amount of protein for
the production of glucose, so as to maintain plasma glucose levels. This occurs
in the liver and is known as gluconeogenesis or the formation of glucose from a
non glucose molecule. 1 gram of protein converts to approximately 0.6-0.7 grams
of glucose, so it is a less efficient energy source. By decreasing energy
efficiency during dieting you increase the amount of energy you use in a given
day, which is very important in dieting.
3. Further, muscle tissue is extremely metabolically active. Because leucine
is able to positively enhance lean mass, it is able to maintain an overall
higher metabolic rate for the duration of a dietary intervention.
Leucine is also the major signaling molecule for protein synthesis which is
itself an extremely costly process.
How does
leucine effect the control of plasma glucose levels?
Both the liver and insulin regulate plasma glucose levels. While fasting, or
between meals the liver releases glucose from stored glucose stores and from
gluconeogenesis.
Glucoeneogenesis primarily occurs through amino acids. In particular the amino
acids alanine and glutamine. Branched chain amino acids, such as leucine are
the primary amino acids used to form alanine and glutamine. Therefore
increasing BCAAs from diet does one of two things.
1. It increases the supply of alanine and glutamine for gluconeogenesis and
therefore more stable blood glucose levels
2. It spares muscle tissue which is comprised of 80 % BCAAs!
Higher carbohydrate diets do not provide this amino acid supply and so
individuals may break down their own muscle tissue stores.
A second area to analyze is the transition from absorbative feeding periods,
which is within 2 hours of feeding and post absorbative periods of feeding,
which occurs after the two hours have ended. Recall during this time insulin
remains elevated, even though glucose has returned to fasting levels.
If consuming a high carbohydrate diet, that is lower in protein then insulin
levels will be higher at this stage. The problem is that if glucose is not
supplied by diet (an obvious since this is between meals), then plasma glucose
levels must be maintained by the liver. But insulin suppresses the enzymes in
the liver which produce glucose and which breakdown glycogen to release
glucose. This explains why plasma glucose levels are lower in high carbohydrate
/ low protein diets.
Leucine
not only acts as a precursor to amino acids such as alanine, but it also acts as
a signaling molecule which stimulates this process directly. This it controls
and participates in gluconeogenic processes.
Practical Applications Summed
Clearly leucine provided by
the diet is critical to the bodybuilder. Overall we discussed the following
applications of leucine.
1. In high quality protein diets leucine is approximately 10 % of proteins
consumed, when averaging typical meat, and whey products.
2. Individuals should consume a minimum of 3-4 grams of leucine per sitting.
If consuming whole proteins this amounts to a minimum of 30-40 grams of protein
per feeding. This also supplies the critical essential amino acids needed to
prolong leucine’s effects.
2. The effects of leucine are mainly on protein synthesis, but it also
decreases protein degradation. However, if you want to maximally stimulate
protein balance it is important to understand hat carbohydrates stimulate
insulin, which is the primary suppressor of protein breakdown. Following
training is a good time to take advantage of insulins effects. During normal
feedings, insulin should only be raised by low to moderate GI carbohydrates.
When carbohydrates fade, their anticatabolic effects should be replaced with
other anticatabolic agents, including glutamine, HMB, and a reasonable increase
in essential fatty acids such as EPA, which is itself directly stops protein
breakdown.
3. Leucines effects may only last 2 – 3 hours after ingestion. Thus, frequency
of leucine ingestion must be high. I recommend a minimum of 6 meals a day,
along with 2 essential amino acid feedings containing 10-15 grams of EAAs, and 3
grams of leucine.
4. Pre bed you are preparing to enter into a state of fasting. You should
consume a slow digesting source of protein such as meat or cottage cheese. If
consuming cottage cheese, realize that its slow release will not substantially
raise leucine levels, even through a cup may contain 30 grams of protein and 3
grams of leucine. This is because at any one point only so much leucine is
released and absolute levels are not raised high enough for a drastic increase
in protein synthesis. A current, but as of yet unconfirmed hypothesis is to
raise the essential amino acid content in cottage cheese, by chasing it with a
serving of EAAs rich in leucine. This will mean that the proportion of EAAs
released will be higher even though cottage cheese is a slow digesting protein.
It may facilitate optimal suppression of protein breakdown and protein synthesis
5. Upon waking in the middle of nighttime sleep you are in a highly catabolic
state. Therefore you should have a shake next to your bed which can be quickly
consumed followed by going back to sleep. The shake should again contain 10-20
grams of essential amino acids, 3 grams of leucine, and anticatabolic agents
previously discussed.
6.
During resistance exercise, it is beneficial to provide a rich source of EAAs
prior to and after for recovery.
However, during endurance training if you do not maintain plasma leucine levels
you will lose muscle tissue. Therefore prior to long duration cardio, or when
performing cardio in the morning be sure and first consume EAAs rich in leucine.
This should hinder any lean tissue loss
7. The elderly should bodybuild as it not only increases their muscle tissue
and functionality, but because they can make improvements that are drastic. The
key is that they need to maximally stimulate protein synthesis. If they consume
a meal low in protein, such as a meal with 15 grams of protein they will not
move into positive protein balance. Instead they need to shoot for a minimum of
10-15 grams of EAAs per meal, rich in leucine content. This can occur through
30-40 grams of protein.
8. Carbohydrates are important for performance, but should not dominate a fat
loss diet. Instead protein levels should be a minimum of 1 gram per pound of
bodyweight and perhaps higher. This will stabilize glucose levels, lower
insulin levels, increase insulin sensitivity, and drastically increase fat loss.
That concludes this series. I have also been asked questions on the boards in
regards to this paper by some extremely intellectual members. You can read
these responses here
http://www.abcbodybuilding.com/forum/showflat.php/Cat/0/Number/1218375/an/0/page/0#1218375
If you
are not a member of the forums you can sign up free here
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