| Low
Carb Diets: Part 3 |
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The metabolism is regulated
in all of its physiological and biochemical processes
by a group of extremely biologically potent compounds
called hormones. In general, there are five hormone
systems that govern the processes of energy input
and output. The Insulin/Glucagon system, the |
Testosterone-Estrogen/Cortisol system, the Growth Hormone/IGF
system, the Catecholamine or Adrenaline system and the
Thyroid system. All of these are interactive and interdependant,
and the conditions in one system are often related to
the conditions in the other systems.
Insulin and glucagon are both produced in the pancreas,
and both function primarily in blood sugar regulation.
Insulin facilitates glucose uptake and use by its target
cells, and acts to lower blood glucose levels. Glucagon
stimulates the breakdown of stored glycogen and the release
of glucose from the liver when blood glucose is low, and
acts to raise blood glucose levels. When you eat a meal
containing carbohydrates, they are broken down to glucose
and absorbed into the blood. As the glucose gets absorbed,
its level in the blood rises (slowly or quickly depending
on the Glycemic Index of the carbohydrate), and insulin
is released to allow the glucose access to its target
tissues. Without insulin, glucose can not enter cells
neither to be stored as glycogen nor used for energy.
When you exercise and use glucose, glucagon is released
to signal the release of more glucose into the blood.
In this way, these two hormones are constantly cooperating
and responding to each other and to their environments,
in order to maintain normal blood glucose levels.
Besides assisting in the storage and utilization of glucose,
insulin does the same to amino acids and fats. This means
that whenever insulin is released, you are storing fat.
The substance that causes the greatest release if insulin
is glucose. Any time carbohydrates are ingested, they
are broken down to glucose, and insulin is released. The
rate at which a carbohydrate is broken down and absorbed
into the blood is measured on a scale known as the Glycemic
Index or GI. In general, the higher the GI of a carbohydrate,
the greater the amount of insulin that will be released
upon its absorbtion.
Other factors that affect the rate and magnitude of insulin
release include the amount of carbohydrate, the presence
of protein (the combination of protein and carbohydrate
causes greater increases in insulin levels than carbohydrates
alone), the frequency and regularity of feeding, the length
of time between feedings (the longer between feedings,
the lower glucose levels will drop and the higher they
will rise after feeding), the fitness of the individual
and overconsumption of refined carbohydrates that has
led to insulin resistence.
People who overconsume carbohydrates tend to have higher
resting insulin levels. This means that not only are they
storing excess carbohydrate as fat, but the entire fat
storing procress is being reinforced by the presence of
insulin. In fact, chronic overconsumption of carbohydrates
can lead to a blunting of the entire insulin mechanism,
such that target cells become resistent to insulin and
no longer act to allow access to glucose. This causes
glucose accumulate and rise in the blood, causing more
insulin to be released. All of this encourages the process
of obesity, and eventually the insulin resistence can
progress to full-blown Type 2 adult-onset diabetes.
By reducing dietary carbohydrate levels, the level of
insulin can be minimized, and its fat storing effects
can be reduced. This is the scientific principle that
is the foundation of low carbohydrate diets. Obviously,
this principal applies mostly to individuals who consume
large quantities of refined and simple carbohydrates,
and not everyone can benefit from carbohydrate reduction.
Individuals who do not overconsume carbohydrates or who
consume carbohydrates that are low on the GI may find
a low-carbohydrate diet not only ineffective, but counterproductive
as well. Testosterone, estrogen and cortisol are all steroid
hormones. Although their physiology and biochemistry are
quite dissimilar, they can be viewed as functioning together
to support the two opposite sides of the metabolism.
Testosterone and estrogen function in support of Anabolic
processes. These include the processes that function in
tissue building and repair and energy storage, like muscle
building and tissue repair and secondary gender-associated
characteristics (ie.muscle mass in males and softer skin
in females). Cortisol functions in support of Catabolic
processes. These include the processes that function in
tissue breakdown and energy use, like breaking down and
removing damaged tissue to allow new tissue to be built,
or breaking down stored fat to use for energy.
Testosterone and estrogen differ in their regulation of
secondary gender-associated characteristics. For the purposes
of this discussion, we will focus on their opposite effect
on fat: testosterone promotes mobilization of fat and
estrogen promotes storage of fat. This means that in general
males tend to be naturally leaner than females.
Cortisol, produced in the adrenal cortex, is known as
the 'stress' hormone. It acts as an insulin antagonist,
promotes fat and protein breakdown, conserves glucose
and it causes an increase in gluconeogenesis. Unfortunately,
the body tends to break down its muscle tissue to obtain
amino acids for the gluconeogenic process. In this way,
muscle can be viewed as a storage form of amino acids,
readily made available to make up for a lack of carbohydrate.
However, for the purpose of fat loss, losing muscle is
a problem, since, in fact, muscle burns fat and losing
muscle can lead to a reduction in Resting Metabolic Rate
(RMR). So, although cortisol does act to mobilize stored
fats, its presence also encourages muscle wasting.
On one hand, it can save our lives during periods of starvation,
but it acts as a 'double-edged sword' for people interested
in long-term weight loss and dieting.
This is where the muscle-preserving and building effects
of resistence training can be of great use. It should
be noted that building muscle requires the presence of
enough glucose to prevent muscle wasting due to gluconeogenesis.
Also, resistence training draws heavily on glycogen stores,
and training can suffer if these stores become chronically
depleted.
Therefore, a post-workout recovery meal/shake should include
carbohydrates (and protein!), in order to refuel glycogen
stores after training and to promote muscle building.
The amount of post-workout carbohydrate that is required
depends mainly on the type, duration and intensity of
training. It should also be noted that if the post-workout
meal/shake is low in fat, the likelihood that this meal
will lead to fat storage is very low, despite any increases
in insulin level following the ingestion of the carbohydrate.
The other steroid hormones, testosterone (produced in
the testes of men and produced as dehydroepiandrosterone
in the adrenal cortex in both sexes) and estrogen (produced
in the ovaries of females and in the adrenal cortex of
both sexes) are less affected by carbohydrate levels,
and more affected by dietary fat intake. In this case,
the law of supply and demand applies. The steroid hormones
are all derived from the same basic building block, another
steroid compound known as Cholesterol. Cholesterol is
obtained in the diet from animal sources (meats, dairy),
but we possess the metabolic pathway to build it from
fat, and thus from any macronutrient. This metabolic pathway
is dependent on the intake of fat, therefore it slows
down when dietary fat is low, and less steroid hormone
is produced. This affects both testosterone and estrogen.
Women are less affected by this since they tend to be
higher in bodyfat than men, although there are incidences
where female athletes and female bodybuilders cease to
menstruate because of lack of available female hormones.
Men, on the other hand, can be greatly affected by their
intake of fat. In a diet of 15% fat or less, there can
be a decrease in testosterone production and in a diet
of 40% fat, there can be an increase in testosterone production.
If carbohydrates are resticted along with fat, there is
a fairly great risk of muscle wasting. If cortisol levels
rise while testosterone levels drop, the relative amount
of muscle wasting will be greater than if testosterone
levels are maintained or even increased.
Testosterone provides a natural mechanism to protect against
the fat storing effects of insulin and the muscle wasting
effects of cortisol. It is to the advantage of anyone
interested in losing fat, to maximize the potential support
provided by testosterone. Reducing dietary fat too low
can lead to a reduction of testosterone, especially in
men. In general fat should be kept between 15% and 40%
of the total caloric intake to prevent testosterone reduction.
Resistence training will also increase testosterone levels
in men, but not to any great extent in women. Even if
the relative increase in testosterone levels associated
with resistence training will be greater in men than in
women, women can still benefit greatly from resistence
training.
Estrogen, the 'female' hormone, poses an unfair disadvantage
for women trying to lose fat. Although it is not directly
responsible for fat storage like insulin, it is nontheless
responsible for the type of fat deposition that is associated
with female gender characteristics. For example, insulin
might be responsible for increasing storage of fat around
the hips, thighs, buttocks, abdomen and other typically
female fatty areas, but estrogen is responsible for directing
storage to these areas. In combination, estrogen and insulin
create quite a potent fattening mechanism. Add to that
lack of physical activity and you have a powerful ct weight-gain
formula. Regular physical activity, including resistence
training, combined with some form of glycemic control
dietary protocol can greatly affect fat loss in women.
The Growth Hormone (GH)/Insulin-like Growth Factors (IGF)
system is the fat-loss/muscle-building/low carbohydrate
superformula. GH, produced in the anterior pituitary gland,
has the following actions: it decreases glucose utilization,
decreases glycogen synthesis, increases amino acid transport
across cell membranes, increases protein and collagen
synthesis, increases breakdown and utilization of fatty
acids, increases availability of glucose and amino acids,
stimulates cartilage growth, increases retention of nitrogen,
sodium, potassium and phosphorus.
GH gives ideal metabolic support for a low-carbohydrate
dietary protocol. It spares glucose, mobilizes and burns
more fat, builds muscle, tendons, ligaments and cartilage
and sets up good nutritional conditions for repair of
tissues. In general growth hormone is released in pulses
at intervals during the course of 24 hours. There is a
large degree of variability with respect to the frequency
and intensity of these pulses. Generally, females have
higher resting levels of GH than men, and so perhaps mother
nature has compensated for higher estrogen levels by giving
women higher GH levels.
Several factors are known to cause the release of GH.
These include fasting, low blood glucose, stress, injury
or trauma, fever, and dopaminergic agents (Neurotransmitters).
Resistence training can increase the production of GH.
In particular, lactic acid acts as a potent stimulus for
the release of GH. Resistence training protocols that
produce greater amounts of lactic acid tend to increase
GH production. Also, GH production is greatest during
Slow Wave Sleep (SWS). Missing sleep can disrupt normal
circadian rhythms, and this can lead to a reduction of
the GH that is released during SWS.
One of the ways that GH acts is through a group of intermediate
messenger proteins collectively known as Insulin-like
Growth Factors or IGF's. In particular, IGF-1 is the messenger
known to be active in protein synthesis in cells. This
is another factor which can be instrumental in the prevention
of muscle wasting associated with hypocaloric and especially
low-carbohydrate dietary protocols. IGF-1 is sensitive
to feeding protocols, especially when an individual engages
in multiset resistence training. Studies have shown that
pre and post workout carbohydrate/protein supplementation
leads to greater increases in IGF-1 values, illustrating
the need for appropriate supplementation to fully support
and optimize fat loss through diet and exercise.
The Adrenaline or Catecholamine system is also known as
the 'fight or flight' system. It includes the Catecholamine
hormones adrenaline, noradrenaline and dopamine. Adrenaline
primes our body for stress and physical activity. Examples
of some of its actions include increased transmission
of nerve impulses, dilation of blood vessels in working
muscles, increased heart rate, elevated blood pressure,
mobilisation of fat and glucose, and constriction of blood
vessels leading to organs of the digestive tract.
It should be noted that many of the actions of the adrenaline
system can take place in the absence of physical activity.
Stress, emotions, anticipation of movement can all causes
an increase in the adrenaline response in the absence
of physical activity. Chronic stress can lead to a state
of chronically elevated adrenaline, which in the absence
of physical activity and the ensuing 'rest and recovery'
period, and cause a whole range of physical and psycological
health problems. The Sympathetic and Parasympathetic divide
the nervous system into two antagonistic main branches,
which represents the two sides of a very ancient survival
mechanism. When the level of adrenaline rises above a
specific threshold value, it acts upon the sympathetic
nervous system to engage the 'fight or flight' system,
and when the adrenaline level drops below a specific threshold,
the parasympathetic system will re-engage, and the body
will settle back down to 'rest and recover'. An easy way
to capitalize on the energy using effects of adrenaline
is to wait for an hour after stopping cardiovascular exercise
before eating. This allows the adrenaline system to taper
down slowly, so that you can capitalize even further on
its calorie burning effects.
Engaging the sympathetic system often means the suppression
of the parasympathetic system. For example, digestion
of food will slow to a halt in favor of the 'fight or
flight' response, so that if food is eaten right before
or during exercise, it will remain undigested, and physiological
priority will go to the processes involved in physical
activity. This is why you shouldn't eat right before swimming.
Also, food can interfere with the adrenaline system. Ingestion
of a high GI carbohydrate right before or during physical
activity will cause the release of insulin, which will
interfere with the processes of energy mobilization and
utilization, and it can cause an individual to feel sluggish
and physically weak, as though they are working against
the grain. As long as activity continues, the adrenaline
system will continue to try and dominate the metabolim
in direct opposition to insulin. Once physical activity
ceases, ingested food coaxes the body from a state of
'fight or flight' to a state of 'rest and recovery'. However,
an 8% glucose solution can be absorbed without causing
a rise in insulin, and ultra-endurance athletes often
rely on these to prevent glycogen depletion.
The Thyroid system, consisting of the protein-iodine hormones
Thyroxine (T4) and Triiodothyronine (T3), acts to regulate
the Resting Metabolic Rate (RMR). It governs all the other
systems by adjusting energy expenditure in such a way
that is not affected directly by diet. Although thyroid
production responds to overall energy intake in its regulation
of RMR, it does so within genetically predetermined parameters
that limits the effects of outside influences like diet.
Similar to the actions of other systems and hormones,
the RMR is kept within a specific range by the constant
secretion/feedback of the thyroid hormones. When the metabolic
rate drops below a specific threshold value, the output
of thyroid hormones increases and the RMR increases. When
there is a chronic increase in the RMR, the output of
thyroid hormones decreases and the RMR drops. Three percent
of obese people suffer from an abnormally functioning
thyroid gland. In these individuals, thyroid output is
abnormally low, and weight gain is a result of an abnormally
slow RMR.
The RMR is held fairly constant throughout one's lifetime.
Exercise can increase energy output even at rest, and
thus affects the RMR. Resistence exercise that increases
muscle mass causes an increase in daily energy expenditure
in support of the extra muscle tissue. More muscle spends
more energy. In fact, this is one of the best ways that
an individual can affect the RMR. Aerobic exercise increases
the efficiency and fluidity of all the energy using pathways.
Individuals who engage in regular aerobic activity have
higher RMR values than untrained individuals of the same
lean body mass. By combining resistance and aerobic exercise,
an individual can maximize their natural RMR.
Conclusions - to carb or not to carb
It should be clear that carbohydrate restriction is
not necessarily the ideal way to achieve fat loss, and
can even be counterproductive. The potential for ketoacidosis
(see part 2 of this article) and muscle wasting, the
looming risk of heart disease and the discomfort and
inconvenience tend to outweigh the possible benefits.
However, in conjunction with exercise, carbohydrate
restriction can be useful in individuals who chronically
overconsume them, at least in the short term. In the
long-term, even carb addicts should eventually reintroduce
low GI or 'smart carbs' back into the diet. Anyone else
should design their protocol around a mixed diet based
on an energy deficit, where portion sizes are reduced.
Also relying on low GI carbohydrates or 'smart carbs'
can be a simple and effective way for anyone to improve
glycemic control.
If you still really want to cut carbs, cut them at night.
This can be useful for people who have developped the
habit of late-night snacking (especially carb addicts),
skipping breakfast, skipping lunch, not eating all day,
eating a huge meal at night or any combination of these.
All of these scenarios have the potential for causing
an insulin nightmare. Besides, reducing insulin secretion,
cutting carbs at night also tends to leave the appetite
unsatiated, so that you will ultimately be hungrier
in the morning. Eating a larger breakfast will give
you enough energy to get through your day productively,
and you will be less hungry at night. Essentially, cutting
carbs at night can help you reset your appetite. As
long as enough carbohydrates are consumed during the
day, eliminating them at night will not only pose absolutely
no health risks, but may actually be beneficial. During
sleep, we are protected from ketoacidosis and muscle
wasting by the carbohydrates that were eaten during
the day and by the glucose sparing effects of GH released
during SWS.
It may be fairly evident that the delicate interpay
between all of the metabolic variables is very complex,
and the degree of individual variation is probably infinite.With
this in mind, it seems fairly logical to assume that
no two people will react the same way to any given protocol,
and that there is no single 'magic' solution for everyone.
But what about all those diets and all those people
who lost all that weight? They are not you. You have
to experiment with your own body and see how it responds
to different combinations of diet and exercise. Understanding
your particular metabolic idiosyncracies is a lifelong
process of self-discovery, and it can be fun and very
rewarding. Take notes, be honest and accurate, don't
be rigid or overly-strict with yourself, don't be afraid
to change your routines when necessary, and be patient.
Learn as much as possible about the underlying scientific
principles behind dietary modification and exercise
so that you can apply them properly. Don't be afraid
to enlist the advice of a registered dieticien, nutritionist
or fitness professional.
References
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lipoprotein lipids, apolipoproteins, lipoprotein (a),
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2. ASCN/AIN Task force on Trans Fatty
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18. http://www.americanheart.org/presenter.jhtml?identifier=4582.
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Sam Torontour, B.Sc.,
C.S.C.S. is an experienced personal trainer and
certified strength and conditioning specialist with
over 15 years experience as a fitness professional.
With a Bachelor of Science degree in Exercise Science
and a minor in Biology from Concordia University,
he possesses a thorough scientific understanding
of the workings of the human body, nutrition and
exercise. |
| He is certified by the National Strength and Conditioning
Association (NSCA) as a Certified Strength and Conditioning
Specialist (CSCS) and has expertise in a wide variety
of areas. His specialties include physique transformation,
athletic preparation, muscle balance and posture,
flexibility, nutrition and supplementation. He is
also an instructor of Muay Thai (an ancient martial
art developed in Thailand). He has worked with males
and females of all ages and from all walks of life,
including students, older adults, teens and professionals.
He is presently working at Gym L’Apogée
on St. Laurent Boulevard in Montreal, and also works
with clients at their homes. |
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