I think that most of us have
tried to go on a diet at least once in our lives. And it was probably because
we wanted to lose weight (or still do). Weight loss is one of the, if not the
most, common reason why people would want to go on a diet. There are many
different reasons why a person would want to do this – maybe it’s for fitness or
sports, maybe health reasons, or simply vanity.
One of the most popular diets in the past
decade or so was the Atkins Diet. In the 1990s Dr. Atkins published Dr.
Atkins New Diet Revolution and it would start a new trend that would get people
all over the world hooked. Other doctors would soon begin to publish books
based on the same principles. This was the
“low-carb craze”, and it people everywhere were on it from the late 90s until
it peaked in 2004.
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| weight loss |
The premise was
simple. The body normally burns
carbohydrates for fuel. By restricting carbohydrates drastically to a mere
fraction of a normal diet, the body goes into a different metabolic state
whereby it burns its own fat for fuel. As a result, the body switches from
being a carbohydrate-burning organism into a fat-burning one. When the fat
stores become the primary energy source, the person loses weight. This is why
low-carbohydrate diets have become popular, and effective, especially among
obese people (Nordqvist, 2010) .
However, one effect of a low-carbohydrate diet many people probably don't know is
ketosis. Ketosis
is the medical condition in which an individual has elevated levels of ketone
bodies in the blood and urine. A person in ketosis is getting energy from ketones.
When the body is in ketosis, you tend to feel less hungry, and thus you're
likely to eat less than you might otherwise (Gelfand, 2010) .
Okay, so how does having a low-carbohydrate
diet lead to a person having elevated ketone levels in the body? The problem starts
when the body does not have enough glucose (probably due to the diet). Humans
can convert some amino acids into glucose (by a process called gluconeogenesis)
but cannot do this for fatty acids. Since the body also needs amino acids for
proteins, it can’t break down plenty amino acids into glucose. This poses a problem
for the brain, since it’s normally fuelled solely by glucose, and the fatty
acids can’t cross the blood–brain barrier. Fortunately, the liver can use fatty
acids to break down and synthesize three ketone bodies: β-hydroxybutyrate, acetoacetate and acetone. These ketone bodies
enter the brain and substitute for glucose (Ketogenic diet, 2010) . This is why people
taking the low-carbohydrate diets are very susceptible to excess levels of
ketone bodies in the blood. Ketosis can also occur in people experiencing Type
1 diabetes (not enough insulin), alcoholism, or starvation.
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| The three ketone bodies |
Pathway
Here is the how the fatty acids are broken
down in more detail. First, fatty acids are enzymatically broken down in
β-oxidation to form acetyl-CoA. Under normal conditions, acetyl-CoA would be further
oxidized and its energy transferred as electrons to NADH, FADH2, and
GTP in the citric acid cycle. However, when fatty acid catabolism by
β-oxidation is predominant, the entry of acetyl-CoA to the citric acid cycle is
impaired because the citric acid cycle intermediates (mainly oxaloacetate) have
been depleted to feed the gluconeogenesis pathway. This results in the
accumulation excess of acetyl-CoA. The excess acetyl-CoA would then be used for
the formation of ketone bodies (Ketogenesis, 2010) .
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| Formation of ketone bodies |
HMG-CoA is then cleaved by HMG-CoA lyase to
acetoacetate and acetyl-CoA. The product, acetoacetate, is at the junction
leading to 2 reactions: (1) non-enzymatic decarboxylation into acetone, or (2)
reduction to D-β-hydroxybutyrate (Boyer, 2006) .
Is it dangerous?
Two of the
ketone bodies produced – acetoacetate and hydroxybutyrate – are relatively
strong acids. The blood can usually buffer to keep the pH of the blood within
normal range. However, in severe ketosis, blood pH can drop below 7.35 causing
an acidosis, or more specific, ketoacidosis (Ketosis, 2010) . Untreated
acidosis is dangerous and can lead to coma or death. Typically, people with type 1 diabetes are vulnerable to
ketoacidosis, as it is sometimes confused with normal ketosis. The body
normally circumvents this state by producing insulin, but people with type 1
diabetes are unable to produce insulin (Dolson, 2008) .
Individuals
on low-carbohydrate diets are in a mild ketotic state. Although a mild state of
ketosis is relatively not dangerous, physiological damage would still occur.
Effects of a mild state of ketosis would include:
1. dehydration
(from excessive urination to get rid of the acids from the body),
2. electrolyte
imbalance (from the loss of Na+ and K+ with acids in urine, kidney stress),
3. difficulty
in thought concentration,
4. bad
breath (from the acetone expelled through our breath),
5. degradation
of protein in muscle tissue (since the amino acids are used to replenish
glucose stores).
Individuals can
prevent severe ketosis by keeping track of the level of ketones in their urine through
purchasing test strips such as Ketostix (Boyer, 2006) .
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| Ketostix |
What should you do?
Most of the theories
of weight loss remain unproven. Because each person’s body and metabolism is
different, every diet’s effect would vary from person to person. Most experts
are concerned that low-carb diets can cause a multitude of problems,
particularly for the large segment of the population that is at risk for heart
disease. Moreover, the diet doesn't permit a high intake of fruits and
vegetables.
Also, nutritionists recommend that individuals on low carbohydrate/low fat/high
protein diets should consume large quantities of water and supplement their
diet with vitamins and salt.
I have heard many
stories about how people would regain the weight they lost after stopping the
diet. The experts say that in order to achieve permanent weight loss you must not
only change your diet, but also your lifestyle. This means following a lower
calorie diet that includes grains, legumes, fruits, and vegetables combined
with regular physical exercise. Be sure to talk with your doctor or
nutritionist to determine what the right diet and approach is for you (Gelfand, 2010) .
Treatment for epilepsy
It is interesting to find out that a
ketogenic diet – a high fat, adequate protein, low carbohydrate diet – also works
as a treatment for epilepsy patients. The diet, which mimics aspects of
starvation by forcing the body to burn fats rather than carbohydrates, has been
shown to reduce the frequency of epileptic seizures (Ketogenic
diet, 2010) .
According to The Epilepsy Foundation, it has been shown to help two in
every three children who tried it. Furthermore, seizures have stopped completely
in one third of the cases (Nordqvist, 2010) .
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| Comparison between a normal and epileptic brain |
Right now, doctors don't know exactly why
such a diet prevents seizures. Many hypotheses have been put forward to explain
how the ketogenic diet works, yet it remains a mystery. It is also unknown why
studies have shown that this diet is more effective for children. As of 2008,
research in this area is regarded as having insufficient positive data to
warrant clinical use. The ketogenic diet also has some side effects – like dehydration,
constipation, occasionally kidney stones, and other side effects – all of which
make careful monitoring necessary (Nordqvist, 2010) .
Other Possible Uses
Multiple uses
of the ketogenic diet are still being investigated. All reported studies
to date are very preliminary. Neurodegenerative disorders such as amyotrophic lateral sclerosis, Alzheimer's
disease and Parkinson's disease provide a unique opportunity to study
cellular protection via dietary means. Psychiatric disorders have also been treated with the ketogenic
diet but the mechanism of action of the
ketogenic diet for psychiatric
disorders is still unclear. In addition, the diet may
have uses beyond neurologic disorders. Very preliminary studies
indicate that the ketogenic diet may be useful in conditions that
involve an imbalance of glucose metabolism, including type 2
diabetes mellitus and polycystic ovary syndrome. The diet has been
described for use in hypercholesterolemia. Other studies have been made for the
future use of the diet as treatment for the following: astrocytomas (a type of
brain tumor), autism, depression, and migraine headaches (Freeman, Kossoff, & Hartman,
2007) .
Works Cited
Boyer, R. (2006). Concepts in
Biochemistry. John Wiley & Sons.
Dolson, L. (2008, July 5). What is
Ketosis? Retrieved October 6, 2010, from About.com:
http://lowcarbdiets.about.com/od/faq/f/whatisketosis.htm
Freeman, J. M., Kossoff, E. H., &
Hartman, A. L. (2007, March 1). The Ketogenic Diet: One Decade Later. Pediatrics
(Vol. 119) , 535-543.
Gelfand, J. L. (2010, March 5). High
Protein, Low Carb Diets. Retrieved October 6, 2010, from WebMD:
http://women.webmd.com/guide/high-protein-low-carbohydrate-diets
Ketogenesis. (2010, September 30). Retrieved October 6, 2010, from Wikipedia:
http://en.wikipedia.org/wiki/Ketogenesis
Ketogenic diet. (2010, September 28). Retrieved October 6, 2010, from Wikipedia:
http://en.wikipedia.org/wiki/Ketogenic_diet
Nordqvist, C. (2010, March 2). What Is
Ketosis? What Causes Ketosis? Retrieved October 6, 2010, from Medical News
Today: http://www.medicalnewstoday.com/articles/180858.php