Ketosis Diets: short-term benefits, long-term concerns , and
problematic studies
Introduction
Many health professionals, such as clinicians and health
officials, believe that America is currently experiencing an
epidemic in obesity.1 Obesity is a condition in which the fatty
tissue in humans exceeds healthy limitations.
In the past
twenty years, the average American male weight has risen by
twelve pounds and the average American female weight has risen
by ten pounds (Cutler, Glaeser & Shapiro, pg. 1, 2003).
Diseases that are associated with obesity include cardiovascular
disease, diabetes mellitus type 2, sleep apnea, and
osteoarthritis which are also on the rise in the United States
(Cutler, Glaeser & Shapiro, 2003).
This has led many
researchers and clinicians to stress the importance of the
social aspects of obesity.
There have been Senate
subcommittee’s formed to investigate the “obesity epidemic” as
well a $4.1 million USDA "Team Nutrition" program to teach
children about healthful eating (Kersh and Morone, pg 10, 2002).
It has also sparked interest in quick fixes and diet plans
within the last few decades.
Weight-Issues
So why is obesity an epidemic in the United States?
In
order to gain excessive weight, the human body must consume more
energy than it expends.
Energy is measured/defined by the
Calorie (kcal), with dietary energy coming from carbohydrate (4
kcal/g), fat (9 kcal/g), and protein (4 kcal/g).
If the body
consumes more calories than required, it will store those extra
1
Cutler, Glaeser & Shapiro, pg. 1, 2003; Kersh and Morone, pg 10, 2002; Pi-Sunyer, pg. 1-4, 1993
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calories as fat, predominantly within adipose tissue.
The body
can burn calories in various ways in response to needs. Basal
metabolic rate is the amount of energy needed to maintain bodily
function running at rest (i.e. breathing, blood circulation);
the thermic effect of food is the amount of energy needed for
digestion of foods; and through daily physical activity which
can vary greatly whether we have a desk job or go to the gym
regularly (Cutler, Glaeser & Shapiro, pg 1, 2003).
The gain in
weight currently sweeping the nation is believed to be due more
to a rise in caloric intake and not a reduction of physical
activity (Cutler, Glaeser & Shapiro, pg. 1, 2003).
Some of the
factors that Cutler, Glaeser & Shapiro suggest in their article
are innovations in food production, which have led to the lower
cost of prepared foods.
However, this lower cost of convenience
food has brought with it a high cost to America’s health.
The
benefits of weight-loss, which include improvement in insulin
sensitivity, glucose disposal, hypertension, triglyceride
levels, and pulmonary function (Pi-Sunyer, pg. 1-4, 1993), are
an illusive but crucial goal for a growing number of Americans.
Unfortunately, complicating factors arise when trying to choose
the best weight loss diet: short-term versus long-term benefits
may vary, and many studies designed to analyze a given diet’s
efficacy are plagued with methodological flaws and confounding
factors.
Ketosis as a Method of Dieting
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One particular type of diet has been at the center of
controversy for quite some time now.
These diets, low in
carbohydrates and high in protein, have been made popular by the
brand name like Atkins, South Beach Diet, Kimkins and The Zone
Diet.
The ever growing popularity of diets is evident by book
sales that describe each.
The Atkins diet books alone have sold
well over 45 million copies (Astrup et al, pg 1, 2004).
The
entire diet industry has an estimated $36 billion dollars spent
on it annually (Kersh and Morone, pg 3, 2002).
The rationale for these types of low carbohydrate diets is
that forcing the body into ketosis aids weight loss.
Ketosis is
a metabolic process within the human body when there is an
abnormally high breakdown of fatty acids that increases the
level of blood ketone bodies (Dennison, Topping & Carret, pg
789, 2007).
This process replaces the use of glycogen and
glucose as the primary method of energy source within the body.
The liver will begin to excessively convert fatty acids into
energy along with the byproduct of ketone bodies.
These fatty
acids come from the stored fat within adipose tissue.
In order
for the human body to enter into the state of ketosis, intake of
carbohydrates must be limited.
These amounts generally vary
from plan to plan but it is typically less than 30 g of
carbohydrates a day.
Since carbohydrates provide the glucose
necessary for glycolysis and cellular adenosine-triphosphate
(ATP) production, the body needs to find an alternate source of
energy in the absence of carbohydrates.
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Benefits of Ketosis Diets
The benefits of ketosis inducing diets are based on
theoretical effects which have been studied in several openlabel studies; yet they have generated some very positive
reviews and advocates of its use.
For instance, in a six month
long study of 51 subjects (of which 41 adhered) in which the
patients were overweight or obese (body mass index [BMI] = 30 to
60 kg/m2), it was found that a significant amount of weight loss
was achieved by using a very low carbohydrate diet of less than
25 g/d with no caloric limit (Westman, et al, pg 1, 2002).
Subjects also received nutritional supplements (i.e.
vitamins/minerals), exercise recommendations and group support
meetings.
Along with weight loss, subjects also experienced
improved HDL, LDL and triglyceride levels (Westman, et al, pg 1,
2002).2
Brehm, Seeley, Daniels and D’Alessio have also confirmed
the above results in a similar study in 2004.
These researchers
were able to find that there were no negative effects on
important cardiovascular functions at the three-month and sixmonth time frames (Brehm, Seeley, Daniels & D’Alessio, pg 1,
2004).
2
The study also found that low carbohydrate diets that
Ketosis diets have also been used to treat children who have experienced atonic or myoclonic seizures. It has been
found that the seizures decreased by more than 50% almost immediately upon changing over from a glucose producing diet to a
ketosis diet (Freeman & Vining, pg 1, 1999).
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induce ketosis have been significantly more effective in weightloss within the six month period than non-ketosis-inducing diets
(Brehm, Seeley, Daniels & D’Alessio, pg 6, 2004).
Additionally,
the study found that insulin resistance improved overall in
participants of the study (Brehm, Seeley, Daniels & D’Alessio,
pg 1, 2004).
Risks and Problems of Ketosis
The health risks of ketosis diets are continually being
challenged by researchers and clinicians.
While there might be
an advantage to losing weight on a ketosis inducing diet in the
short term, there has been cause for alarm in the longer term
studies.
In a year-long clinical study, a ketosis diet did not
statistically improve LDL cholesterol levels and even worsened
HDL cholesterol levels (Dansinger, Gleason, Griffith, Selker &
Schaefer, pg 8-10, 2005).
Another issue addressed was the low
intake of fiber and calcium while on a high protein low
carbohydrate diet, which could lead to long term negative
impacts on gastrointestinal and bone health (Brehm, Seeley,
Daniels & D’Alessio, pg 6, 2004).
While some studies claim that there is an improvement in
high-density lipoprotein, low-density lipoprotein and the ratio
of total cholesterol to high-density lipoprotein, they
acknowledge that the improvement is due to changes in levels of
adipose tissue and not the mechanism of a low carbohydrate diet
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per se (Shai, et. Al, 2008).
In the same study, researchers
showed that a diet that was low in red meats and had controlled
caloric intakes had better effects on HDL, LDL and cholesterol
ratio levels than a low-carbohydrate plan (Shai, et. Al, 2008).
As parents try to find methods to help their children with
weight-loss before it becomes an adult issue, they have turned
to popular methods such as ketosis diet programs.
In a study of
overweight and obese children, it was shown that a high-fat
ketogenic diet lowered HDL cholesterol significantly
(Kwiterovich, Vining, Pyzik, Skolasky, Freeman, pg. 1, 2003).
Furthermore, participants in the study had significant increase
in LDL cholesterol levels after six months on their meal plan
and only one in six participants had a cholesterol or
triglyceride level in the acceptable range (Kwiterovich, Vining,
Pyzik, Skolasky, Freeman, pg. 8, 2003).
Children following
these ketogenic diets have higher rates of dehydration,
constipation, and kidney stones (Denke, pg 2, 2001).
High-
protein, low-carbohydrate diets can generate a higher acid load;
this can result in metabolic acidosis. Metabolic acidosis
promotes calcium mobilization from bone and contributes to bone
diseases such as osteoporosis (Denke, pg 3, 2001).
Ketogenic diets have been linked to several neurological
issues such as dizziness, headaches, fatigue, and irritability
(Blackburn, Phillips & Morreale, pg. 5, 2001). As has been
previously noted, ketogenic diets have improved spontaneous
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seizures within children; this is true for laboratory rats as
well.
However, among these same rats there were adverse effects
on brain growth and severe impairment in visual-spatial memory
(Zhao, Stafstrom,
Fu, Hu &
Holmes, pg. 1, 2004).
This has
troubling implications, even if it is an animal study, for using
this diet to treat obesity among children.
Another issue is the ability to keep the weight off from a
ketosis diet.
The number of people on ketosis diets is very low
among the 3,000 subjects found in the National Weight Loss
Registry who have lost at least 30 pounds and have kept the
weight off for at least six years (Larson & Murray-Davis, pg. 4,
2005).
Confounding Factors of Ketosis Studies
There are also questionable results concerning whether
ketosis diets actually produce a greater weight-loss effect over
other conventional programs.
Researchers have found that the
immediate weight loss within the first few weeks is greater from
a ketosis diet because it promotes a diet induced diuresis.
This is because water weight is released with glycogen stores (2
g water per 1 g glycogen), as glycogen stores in the liver and
kidney are no longer needed when ketosis takes over as the main
source of energy (Denke, pg 1, 2001).
This water weight loss can be accounted for in a twelveweek study; participants on the low-carbohydrate diet lost about
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2.5 kg more than those on the low-calorie diet.
This might be
due to the loss of glycogen stores and associated water, which
can be as great as 2 kg (Buchholz & Schoeller, pg. 6, 2004).
The real issue lies with the Atwater factors (the
calories each gram of fat, protein, and carbohydrate contain);
it has been shown that the energy (calories) we place into our
bodies metabolizes differently and the results of greater
weight-loss could be due to the influence of satiety of high
protein intake, which is a common trait in low-carbohydrate
diets (Buchholz & Schoeller, pg. 7, 2004).
It can also be noted that underreporting should be of note
between diet treatments (i.e. ketogenic diets and/or low calorie
diets that allow for mixed macronutrients); this can be possibly
explained due to that fact that a high protein – low
carbohydrate diet increases satiety between meals which lead to
reduced food intake (Johnstone, Horgan, Murison, Bremner, &
Lobley, pg. 1, 2008).
Other factors for the reported differences in weight loss
are confounding errors, such as treatment groups in a study not
being well matched (Buchholz & Scholeller, pg 6, 2004).
For
instance, men typically lose more fat mass per unit of weight
loss than women; in order to correct this, body composition
should be measured as a variable of quality weight-loss
(Buchholz & Scholeller, pg 6, 2004).
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One study in particular has the low-carbohydrate group
losing more weight than any other group studied (Shai, et. Al,
pg 15, 2008).
While this might seem like a benefit of ketosis-
inducing diets, there may be a confounding factor involved.
The
study indicates that the calorie controlled group of dieters
also exercised more often than any other group (Shai, et. Al, pg
12, 2008).
This opens the methodology to debate since the human
body still requires a specific amount of energy to maintain
bodily function.
It is possible to enter “starvation mode”, in
which the human body won’t give up fat tissue even though it
needs more calories to maintain said bodily functions.
This is
a form of protection the body uses to avoid malnutrition.
A
body that is reducing caloric intake and burning calories via
physical exercise may give up less weight than a diet that has
no caloric restriction but uses another method of fat burning
such as ketosis.
Conclusions
In summary, the United States is suffering from an obesity
epidemic and this epidemic has been associated with many serious
diseases.
In response, Americans have turned to various methods
of dieting to help combat the problem of weight-gain.
Ketosis-
inducing diets have been widely touted as having effective
results for weight-loss, and it does appear that most studies
have concluded that ketosis-induced diets are the most effective
for people looking to loose weight quickly.
However, this might
be where the benefits of ketosis-inducing diets end.
Long-term
studies indicate that even the weight-loss benefits may be
attributable to confounding factors such as satiety, under9|Page
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reporting, water weight loss, etc.
Furthermore, there are
conflicting results on blood lipid levels from various studies.
Clearly there is a need for further research on long-term
benefits and problems relating to ketosis diets.
In the
meantime, caution should be exercised while using these various
methods and individuals should be under the close supervision of
a healthcare provider.
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