Arizona Diet Products Helps You To Lose Weight Quickly and Safely

Carbohydrates comes from ‘hydrates of carbon) or saccharides (Greek meaning “sugar”) are the most abundant of the four major classes of biomolecules, which also include proteins, lipids and nucleic acids. They fill numerous roles in living things, such as the storage and transport of energy (starch glycogen) and structural components (cellulose in plants, chitin in animals). Additionally, carbohydrates and their derivatives play major roles in the working process of the immune system, fertilization, pathogenesis, blood clotting, and development.

Chemically, carbohydrates are simple organic compounds that are aldehydes or ketones with many hydroxyl groups added, usually one on each carbon atom that is not part of the aldehyde or ketone functional group. The basic carbohydrate units are called monosaccharides, such as glucose, galactose, and fructose. The general stoichiometric formula of an unmodified monosaccharide is (C·H₂O) _n, where n is any number of three or greater; however, the use of this word does not follow this exact definition and many molecules with formulae that differ slightly from this are still called carbohydrates, and others that possess formulae agreeing with this general rule are not called carbohydrates (eg formaldehyde).

Monosaccharides can be linked together into polysaccharides in almost limitless ways. Many carbohydrates contain one or more modified monosaccharide units that have had one or more groups replaced or removed. For example, deoxyribose, a component of DNA, is a modified version of ribose; chitin is composed of repeating units of N-acetylglucosamine, a nitrogen-containing form of glucose. The names of carbohydrates often end in the suffix (ose).  

 

 

 

D-glucose is an aldohexose with the formula (C·H₂O) ₆. The red atoms highlight the aldehyde group, and the blue atoms highlight the asymmetric center furthest from the aldehyde; because this -OH is on the right of the Fischer projection, this is a D sugar.

Monosaccharides are the simplest carbohydrates in that they cannot be hydrolyzed to smaller carbohydrates. The general chemical formula of an unmodified monosaccharide is (C•H₂O)_n, where n is any number of three or greater.

 Classification of monosaccharides

The A and β anomers of glucose. Note the position of the anomeric carbon (red or green) relative to the CH₂OH group bound to carbon 5: they are either on the opposite sides (α), or the same side (β).

Monosaccharides are classified according to three different characteristics: the placement of its carbonyl group, the number of carbon atoms it contains, and its chiral handedness. If the carbonyl group is an aldehyde, the monosaccharide is an aldose; if the carbonyl group is a ketone, the monosaccharide is a ketose. Monosaccharides with three carbon atoms are called trioses, those with four are called tetroses, five are called pentoses, and six are hexoses, and so on. These two systems of classification are often combined. For example, glucose is an aldohexose (a six-carbon aldehyde), ribose is an aldopentose (a five-carbon aldehyde), and fructose is a ketohexose (a six-carbon ketone).

Each carbon atom bearing a hydroxyl group (-OH), with the exception of the first and last carbons, are asymmetric, making them stereocenters with two possible configurations each (R or S). Because of this asymmetry, a number of isomers may exist for any given monosaccharide formula. The aldohexose D-glucose, for example, has the formula (C·H₂O)₆, of which all but two of its six carbons atoms are stereogenic, making D-glucose one of 2⁴ = 16 possible stereoisomers. In the case of glyceraldehyde, an aldotriose, there is one pair of possible stereoisomers, which are enantiomers and epimers. 1,3-dihydroxyacetone, the ketose corresponding to the aldose glyceraldehye, is a symmetric molecule with no stereocenters). The assignment of D or L is made according to the orientation of the asymmetric carbon furthest from the carbonyl group: in a standard Fischer projection if the hydroxyl group is on the right the molecule is a D sugar, otherwise it is an L sugar. Because D sugars are biologically far more common, the D is often omitted.

 Conformation

 

 

Glucose can exist in both a straight-chain and ring form.

The aldehyde or ketone group of a straight-chain monosaccharide will react reversibly with a hydroxyl group on a different carbon atom to form a hemiacetal or hemiketal, forming a heterocyclic ring with an oxygen bridge between two carbon atoms. Rings with five and six atoms are called furanose and pyranose forms, respectively, and exist in equilibrium with the straight-chain form.

During the conversion from straight-chain form to cyclic form, the carbon atom containing the carbonyl oxygen, called the anomeric carbon, becomes a chiral center with two possible configurations: the oxygen atom may take a position either above or below the plane of the ring. The resulting possible pair of stereoisomers are called anomers. In the α anomer, the -OH substituent on the anomeric carbon rests on the opposite side (Trans) of the ring from the CH₂OH side branch. The alternative form, in which the CH₂OH substituent and the anomeric hydroxyl are on the same side (cis) of the plane of the ring, is called the β anomer. Because the ring and straight-chain forms readily interconvert, both anomers exist in equilibrium.

 Use in living organisms

Monosaccharides are the major source of fuel for metabolism, being used both as an energy source (glucose being the most important in nature) and in biosynthesis. When monosaccharides are not needed by cells they are quickly converted into another form, such as polysaccharides.

 Disaccharides

 

Sucrose, also known as table sugar, is a common disaccharide. It is composed of two monosaccharides: D-glucose (left) and D-fructose (right).

 

Two joined monosaccharides are called disaccharides and represent the simplest polysaccharides. Examples include sucrose and lactose. They are composed of two monosaccharide units bound together by a covalent bond known as a glycosidic linkage formed via a dehydration reaction, resulting in the loss of a hydrogen atom from one monosaccharide and a hydroxyl group from the other. The formula of unmodified disaccharides is C₁₂H₂₂O₁₁. Although there are numerous kinds of disaccharides, a handful of disaccharides are particularly notable.

Sucrose, pictured to the right, is the most abundant disaccharide and the main form in which carbohydrates are transported in plants. It is composed of one D-glucose molecule and one D-fructose molecule. The systematic name for sucrose, O-α-D-glucopyranosyl-(1→2)-D-fructofuranoside, indicates four things:

• Its monosaccharides: glucose and fructose
• Their ring types: glucose is a pyranose, and fructose is a furanose
• How they are linked together: the oxygen on carbon number 1 (C1) of α-D-glucose is linked to the C2 of D-fructose.
• The -oside suffix indicates that the anomeric carbon of both monosaccharides participates in the glycosidic bond.

Lactose, a disaccharide composed of one D-galactose molecule and one D-glucose molecule, occurs naturally in milk. The systematic name for lactose is O-β-D-galactopyranosyl-(1→4)-D-glucopyranose. Other notable disaccharides include maltose (two D-glucoses linked α-1,4) and cellobiose (two D-glucoses linked β-1,4).

 Oligosaccharides and polysaccharides

 

Amylose is a linear polymer of glucose mainly linked with α(1→4) bonds. It can be made of several thousands of glucose units. It is one of the two components of starch, the other being amylopectin.

 

Oligosaccharides and polysaccharides are composed of longer chains of monosaccharide units bound together by glycosidic bonds. The distinction between the two is based upon the number of monosaccharide units present in the chain. Oligosaccharides typically contain between two and nine monosaccharide units, and polysaccharides contain greater than ten monosaccharide units. Definitions of how large a carbohydrate must be to fall into each category vary according to personal opinion. Examples of oligosaccharides include the disaccharides mentioned above, the trisaccharide raffinose and the tetrasaccharide stachyose.

Oligosaccharides are found as a common form of protein posttranslational modification. Such posttranslational modifications include the Lewis and ABO oligosaccharides responsible for blood group incompatibilities, the alpha-Gal epitope responsible for hyper acute rejection in xenotransplanation, and O-GlcNAc modifications.

Polysaccharides represent an important class of biological polymers. Their function in living organisms is usually either structure or storage related. Starch is used as a storage polysaccharide in plants, being found in the form of both amylose and the branched amylopectin. In animals, the structurally similar but more densely branched glycogen is used instead. Glycogen’s properties allow it to be metabolized more quickly, which suits the active lives of locomotive animals.

Cellulose and chitin are examples of structural polysaccharides. Cellulose is used in the cell walls of plants and other organisms, and is claimed to be the most abundant organic molecule on earth. It has a variety of uses including in the paper and textile industry and as a feedstock for the production of rayon (in the viscose process), cellulose acetate, celluloid and nitrocellulose. Chitin has a similar structure to cellulose but has nitrogen containing side branches, increasing its strength. It is found in arthropod exoskeletons and in the cell walls of some fungi. It has a variety of uses, for example in surgical threads.

Other polysaccharides include callose or laminarin, xylan, mannan, fucoidan, and galactomannan.

 Nutrition

 

 

Grain products: rich sources of complex and simple carbohydrates

Carbohydrates require less water to digest than proteins or fats and are the most common source of energy. Proteins and fat are vital building components for body tissue and cells and are also a source of energy for the body.

Carbohydrates are not essential nutrients: the body can obtain all its energy from protein and fats. The brain cannot burn fat and needs glucose for energy, but the body can make this glucose from protein. Carbohydrates contain 3.75 and proteins 4 kilocalories per gram, respectively, while fats contain 9 kilocalories and alcohol contains 7 kilocalories per gram.

Foods that are high in carbohydrates include breads, pastas, beans, potatoes, bran, rice and cereals.

Based on evidence for risk of heart disease and obesity, the Institute of Medicine recommends that American and Canadian adults get between 40-65% of dietary energy from carbohydrates. The Food and Agriculture Organization and World Health Organization jointly recommend that national dietary guidelines set a goal of 55-75% of total energy from carbohydrates, but only 10% should be from Free sugars (their definition of simple carbohydrates).

 

 Classification

Dietitians and nutritionists commonly classify carbohydrates as simple (monosaccharides and disaccharides) or complex (oligosaccharides and polysaccharides). The term complex carbohydrate was first used in the Senate Select Committee publication Dietary Goals for the United States (1977), where it denoted “fruit, vegetables and whole-grains”. Dietary guidelines generally recommend that complex carbohydrates and nutrient-rich simple carbohydrates such as fruit and dairy products make up the bulk of carbohydrate consumption. The USDA’s Dietary Guidelines for Americans 2005 dispenses with the simple/complex distinction, instead recommending fiber-rich foods and whole grains.

The glycemic index and glycemic load systems are popular alternative classification methods which rank carbohydrate-rich foods based on their effect on blood glucose levels. The insulin index is a similar, more recent classification method which ranks foods based on their effects on blood insulin levels. This system assumes that high glycemic index foods and low glycemic index foods can be mixed to make the intake of high glycemic foods more acceptable.

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Ketosis is a state in metabolism occurring when the liver excessively converts fat into fatty acids and ketone bodies which can be used by the body for energy.
Adipose tissue consists of highly specialized cells which store energy in the form of a triglyceride and release it upon hydrolysis in a process known as lipolysis, yielding three fatty acids and one glycerol molecule. These ketone bodies are a by-product of the lipid metabolic pathway after the fat is converted to energy. Ketoacidosis, by contrast, is the accumulation of excessive keto acids in the blood stream (specifically acetoacetate and beta-hydroxy butyrate).

  Metabolic pathways

Most medical resources regard ketosis as a physiological state associated with chronic starvation. Glucose is regarded as the preferred energy source for all cells in the body with ketosis being regarded as a crisis reaction of the body to a lack of carbohydrates in the diet. In recent years this viewpoint, both the body’s preference for glucose and the dangers associated with ketosis, has been challenged by some doctors.

Ketone bodies, from the breakdown of fatty acids to acetyl groups, are also produced during this state, and are burned throughout the body. Excess ketone bodies will slowly decarboxylate into acetone. That molecule is excreted in the breath and urine. When glycogen stores are not available in the cells (glycogen is primarily created when carbohydrates such as starch and sugar are consumed in the diet), fat (triacylglycerol) is cleaved to give 3 fatty acid chains and 1 glycerol molecule in a process called lipolysis. Most of the body is able to utilize fatty acids as an alternative source of energy in a process where fatty acid chains are cleaved to form acetyl-CoA, which can then be fed into the Krebs cycle. During this process a high concentration of glucagon is present in the serum and this inactivates hexokinase and phosphofructokinase-1 (regulators of glycolysis) indirectly, causing most cells in the body to use fatty acids as their primary energy source. At the same time, glucose is synthesized in the liver from lactic acid, glucogenic amino acids, and glycerol, in a process called gluconeogenesis. This glucose is used exclusively for energy by cells such as neurons and red blood cells.

 Similar conditions

Ketosis should not be confused with ketoacidosis (diabetic ketoacidosis or the less common alcoholic ketoacidosis), which is severe ketosis causing the pH of the blood to drop below 7.2. Ketoacidosis is a medical condition usually caused by diabetes and accompanied by dehydration, hyperglycemia, ketonuria and increased levels of glucagon. The high glucagon, low insulin serum levels signals the body to produce more glucose via gluconeogenesis and glycogenolysis, and ketone bodies via ketogenesis. High levels of glucose causes the failure of tubular reabsorption in the kidneys, causing water to leak into the tubules in a process called osmotic diuresis, causing dehydration and further exacerbating the acidosis.

 Diet

If the diet is changed from a highly glycemic diet to a diet that does not substantially contribute to blood glucose, the body goes through a set of stages to enter ketosis. During the initial stages of this process the adult brain does not burn ketones, however the brain makes immediate use of this important substrate for lipid synthesis in the brain. After about 48 hours of this process, the brain starts burning ketones in order to more directly utilize the energy from the fat stores that are being depended upon, and to reserve the glucose only for its absolute needs, thus avoiding the depletion of the body’s protein store in the muscles.

Whether ketosis takes place can be checked by using special urine test strips such as Ketostix.

Deliberately induced ketosis through a low-carbohydrate diet has been used to treat medical conditions although most such treatments remain controversial.

 

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Low Carbohydrate diet

 

Low-carbohydrate diets or low-carb diets are dietary programs that restrict carbohydrate consumption usually for weight control. Foods high in digestible carbohydrates are limited or replaced with foods containing a higher percentage of proteins and fat.

The precise definition of low-carbohydrate diets varies greatly. The term is most commonly used to refer to ketogenic diets, i.e. diets that restrict carbohydrate intake sufficiently to cause ketosis like the Atkins diet, but some sources consider less restrictive variants to be low-carbohydrate as well. Apart from obesity low-carbohydrate diets are often discussed as treatments for some other conditions, most notably diabetes and epilepsy, although these treatments still remain controversial and lack widespread support.

Beginnings

In 1863 William Banting, an obese English undertaker and coffin maker, published “Letter on Corpulence Addressed to the Public” in which he described a diet for weight control giving up bread, butter, milk, sugar, beer and potatoes. His booklet was widely read; so much so that some people used the term “Banting” for the activity usually called “dieting.”.

In 1967, Dr. Irwin Stillman published The Doctor’s Quick Weight Loss Diet. The “Stillman Diet” is a high-protein, low-carbohydrate and low-fat diet. It is regarded as one of the first low-carbohydrate diets to become popular in the US. Other low-carbohydrate diets in the 1960s included Air Force Diet and the Drinking Man’s Diet. Austrian physician Dr Wolfgang Lutz published his book ‘Leben Ohne Brot’ (Life Without Bread) in 1967. However it was hardly noticed in the English speaking world.

In 1972, Dr. Robert Atkins published Dr. Atkins Diet Revolution which advocated a low-carbohydrate diet he had successfully used in treating patients in the 1960s (having himself developed the diet from an unspecified article published in JAMA). The book met with some success but, because of research at that time suggesting risk factors associated with excess fat and protein, it was widely criticized by the mainstream medical community as being dangerous and misleading, thereby limiting its appeal at the time. Among other things critics pointed out that Dr. Atkins had done little real research into his theories and based them mostly on anecdotal evidence.

The concept of the glycemic index was invented in 1981 by Dr. David Jenkins. This concept evaluates foods according to their insulin demand — with fast digesting simple carbohydrates having a high insulin demand and slower digesting complex carbohydrates such as grains having a lower insulin demand.

Low-carb diets since the 1990s

In the 1990s Dr. Atkins published Dr. Atkins New Diet Revolution and other doctors began to publish books based on the same principles. This has been said to be the beginning of the “low carb craze.” During the late 1990s and early 2000s low-carbohydrate diets became some of the most popular diets in the U.S. (by some accounts as much as 18% of the population was using a low-carbohydrate diet at its peak) and spread to many countries. These were, in fact, noted by some food manufacturers and restaurant chains as substantially affecting their businesses (notably Krispy Kreme). This was in spite of the fact that the mainstream medical community continued to denounce low-carbohydrate diets as being a dangerous trend. It is, however, valuable to note that many of these same doctors and institutions at the same time quietly began altering their own advice to be closer to the low-carbohydrate recommendations (e.g. eating more protein, eating more fiber/less starch, reducing consumption of juices by children). The low-carbohydrate advocates did some adjustments of their own increasingly advocating controlling fat and eliminating trans fat. Many of the diet guides and gurus that appeared at this time intentionally distanced themselves from Atkins and the term low carb (because of the controversies) even though their recommendations were based on largely the same principles (e.g. the Zone diet). As such it is often a matter of debate which diets are really low-carbohydrate and which are not. The 1990s and 2000s also saw the publication of an increased number of clinical studies regarding the effectiveness and safety (pro and con) of low-carbohydrate diets (notably a 2006 NEJM paper by Halton et al. describing a 20-year study).

After 2004 the popularity of this diet trend began to wane significantly although it still remains quite popular. In spite of the decline in popularity this diet trend has continued to quietly garner attention in the medical and nutritional science communities.

 

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Medical Research on Low Carb Diets

 

Low Carb diets became a major weight loss and health maintenance trend during the late 1990s and early 2000s. While their popularity has waned recently from its peak, they still remain popular. This diet trend has stirred major controversies in the medical and nutritional sciences communities and, as yet, there is not a general consensus on their efficacy or safety. As of 2007 the majority of the medical community remains generally opposed to these diets for long term health although studies have reported positive results in both weight loss and improvement in health indicators.

This article summarizes a sampling of the studies and other research that exist related to this diet trend including not only the efficacy of these diets on weight loss, but also their effects on other aspects of health and related topics such as ketosis. This is not a complete listing of all relevant research.

Synopsis

Because of the substantial controversy regarding low-carbohydrate diets, and even disagreements in interpreting the results of specific studies, it is currently difficult to objectively summarize the research in a way that reflects scientific consensus.

Although there has been some research done throughout the twentieth century, most directly relevant scientific studies have occurred in the 1990s and early 2000s and, as such, are relatively new and the results are still debated in the medical community. Supporters and opponents of low-carbohydrate diets frequently cite many articles (some times the same articles) as supporting their positions. One of the fundamental criticisms of those who advocate the low-carbohydrate diets has been the lack of long-term studies evaluating their health risks.

 

 Specific Research

The following is not a complete list of all relevant research but a selected list of articles demonstrating some of the breadth of scientific knowledge available on this subject.

 Journal of the American Medical Association: 1926

Lieb et al., 1926 conducted a case study of Dr. Vilhjalmur Stefansson, an anthropologist and explorer who lived with the Inuit eating a diet consisting almost entirely of meat, fish, and fat. A research team studied Stefansson’s health looking for signs that his “unusual” diet had adversely affected his health. The team was unable to find any health problems in Stefansson and noted that the Inuit themselves also were quite healthy.

 

 The Lancet: 1956

Kekwick and Pawan, 1956 conducted a study of subjects consuming 1000-calorie diets, some 90% protein, some 90% fat, and some 90% carbohydrates. Those on the high fat diet lost the most, the high protein dieters lost somewhat less, and the high carbohydrate dieters actually gained weight on average.

Kekwick and Pawan noted irregularities in their study (patients not fully complying with the parameters of the study). As such the validity of the conclusions has to be questioned.

 Annals of Internal Medicine: 1965

A study conducted in 1965 at the Naval Hospital Oakland (Oakland, California) used a diet of 1000 calories per day, high in fat and limiting carbohydrates to 10 grams (40 calories) daily. Over a ten-day period, subjects on this diet lost more body fat than did a group who fasted completely (Benoit et. al. 1965). Some advocates, such as Atkins, of low-carbohydrate diets have termed this the metabolic advantage of such diets.

 American Journal of Clinical Nutrition: 1997

Holt et al., 1997 performed a study of glucose and insulin responses for test subjects to a variety of foods, both high- and low-carbohydrate. The conclusions state the following.

    Our study was undertaken to test the hypothesis that the postprandial insulin response was not necessarily proportional to the blood glucose response and that nutrients other than carbohydrate influence the overall level of insulinemia … The results of this study confirm and also challenge some of our basic assumptions about the relation between food intake and insulinemia. Within each food group, there was a wide range of insulin responses, despite similarities in nutrient composition … As observed in previous studies, consumption of protein or fat with carbohydrate increases insulin secretion compared with the insulinogenic effect of these nutrients alone … However, some protein and fat-rich foods (eggs, beef, fish, lentils, cheese, cake, and doughnuts) induced as much insulin secretion as did some carbohydrate-rich foods (e.g., beef was equal to brown rice and fish was equal to grain bread).

This study challenges the general assertion that only carbohydrates significantly impact insulin production.

The authors describe their work as “preliminary” and so the results should be judged with caution.

 New England Journal of Medicine: 2003

 

Two important NEJM studies from this year are mentioned here. Samaha et al., 2003 completed a study of 132 obese subjects comparing the efficacy of low-carbohydrate and low-fat diets. The conclusions of the article state the following.

    Severely obese subjects with a high prevalence of diabetes or the metabolic syndrome lost more weight during six months on a carbohydrate-restricted diet than on a calorie- and fat-restricted diet, with a relative improvement in insulin sensitivity and triglyceride levels, even after adjustment for the amount of weight lost. This finding should be interpreted with caution, given the small magnitude of overall and between-group differences in weight loss in these markedly obese subjects and the short duration of the study. Future studies evaluating long-term cardiovascular outcomes are needed before a carbohydrate-restricted diet can be endorsed.

Foster et al., 2003 performed a similar study 63 obese men. Their conclusion was the following.

    The low-carbohydrate diet produced a greater weight loss (absolute difference, approximately 4 percent) than did the conventional diet for the first six months, but the differences were not significant at one year. The low-carbohydrate diet was associated with a greater improvement in some risk factors for coronary heart disease. Adherence was poor and attrition was high in both groups. Longer and larger studies are required to determine the long-term safety and efficacy of low-carbohydrate, high-protein, and high-fat diets.

In essence these studies showed that, setting aside their short-term nature and some safety questions, the low-carbohydrate diet was at least somewhat more effective in weight loss and in improvement of other health issues in an important demographic.

 Journal of the American Medical Association: 2003

Bravata et al., 2003 conducted a literature search study of low-carbohydrate diet studies conducted between 1966 and 2003. The paper stated the following conclusion.

    There is insufficient evidence to make recommendations for or against the use of low-carbohydrate diets, particularly among participants older than age 50 years, for use longer than 90 days, or for diets of 20 g/d or less of carbohydrates. Among the published studies, participant weight loss while using low-carbohydrate diets was principally associated with decreased caloric intake and increased diet duration but not with reduced carbohydrate content.

The study determined that carbohydrate reduction did not significantly contribute more to weight loss than simply reducing calories. The article does state that

    Low-carbohydrate diets had no significant adverse effect on serum lipid, fasting serum glucose, and fasting serum insulin levels, or blood pressure.

 

 Journal of Child Neurology: 2003

Evangeliou et al., 2003 completed a 6-month study of 30 autistic children following a low-carbohydrate, ketogenic diet. The paper stated the following conclusions.

    Of the remaining group who adhered to the diet, 18 of 30 children (60%) [the rest did not complete the study], improvement was recorded in several parameters and in accordance with the Childhood Autism Rating Scale. Significant improvement (> 12 units of the Childhood Autism Rating Scale) was recorded in two patients (pre-Scale: 35.00 +/- 1.41[mean +/- SD]), average improvement (> 8-12 units) in eight patients (pre-Scale: 41.88 +/- 3.14[mean +/- SD]), and minor improvement (2-8 units) in eight patients (pre-Scale: 45.25 +/- 2.76 [mean +/- SD]).

The authors state clearly that the study was limited and the results are preliminary.

 Journal of the American Academy of Neurology: 2003

Kossoff et al., 2003 conducted a small study of six epileptic patients studying the effects of the Atkins diet. The abstract states the following.

    The ketogenic diet is effective for treating seizures in children with epilepsy. The Atkins diet can also induce a ketotic state, but has fewer protein and caloric restrictions, and has been used safely by millions of people worldwide for weight reduction. Six patients, aged 7 to 52 years, were started on the Atkins diet for the treatment of intractable focal and multifocal epilepsy. Five patients maintained moderate to large ketosis for periods of 6 weeks to 24 months; three patients had seizure reduction and were able to reduce antiepileptic medications. This provides preliminary evidence that the Atkins diet may have a role as therapy for patients with medically resistant epilepsy.

In a 2004 Lancet article, Dr. Kossoff also stated that

    The ketogenic diet is a high-fat, adequate protein, low carbohydrate diet that has been used for the treatment of intractable childhood epilepsy since the 1920s … Although less commonly used in later decades because of the increased availability of anticonvulsants, the ketogenic diet has re-emerged as a therapeutic option.

 Annals of Internal Medicine: 2004

Two significant studies can be found in the Annals of Internal Medicine in 2004. Yancy et al., 2004 completed a study of 120 overweight, high-lipid-count subjects comparing the efficacy of low-carbohydrate and low-fat diets. The conclusions of the article state the following.

    Compared with a low-fat diet, a low-carbohydrate diet program had better participant retention and greater weight loss. During active weight loss, serum triglyceride levels decreased more and high-density lipoprotein cholesterol level increased more with the low-carbohydrate diet than with the low-fat diet.

Stern et al., 2004 conducted a one-year study of 132 obese adults. The conclusions state the following.

    Participants on a low-carbohydrate diet had more favorable overall outcomes at 1 year than did those on a conventional diet. Weight loss was similar between groups, but effects on atherogenic dyslipidemia and glycemic control were still more favorable with a low-carbohydrate diet after adjustment for differences in weight loss.

 Nutrition Journal: 2004

Feinman and Fine, 2004 present an argument refuting the “calorie is a calorie” principle cited by some as an argument against the weight-loss benefits of low-carbohydrate diets. The “calorie is a calorie” argument, loosely speaking, states that the laws of thermodynamics imply that calories ingested from any source are burned at the same rate in the body (meaning that, for the purposes of weight loss, all sources of calories are the same).

The paper refutes this (the argument is omitted here) stating the following in the conclusion.

    Thus, ironically the dictum that a “calorie is a calorie” violates the second law of thermodynamics, as a matter of principle.

The authors’ point is that while some have argued that there is no point in comparing the effectiveness of diets based on the sources of calories (proteins, fats, or carbohydrates), the arguments in favor of this viewpoint are not supported by science. This paper is not directly based on any clinical studies but rather is a discussion of basic scientific theory related to this subject.

 Cancer Epidemiology, Biomarkers & Prevention: 2004

Romieu et al. 2004 completed a survey-based study of a selected group of 475 women against a control group of 1391 correlating diet and breast cancer rates. The study concluded the following.

    In this population, a high percentage of calories from carbohydrate, but not from fat, were associated with increased breast cancer risk.

 American Journal of Epidemiology: 2005

Ma et al., 2005 completed a one-year study of 572 healthy adults monitoring their diet and physical activity. The study concluded the following.

    In conclusion, results from our study suggest that daily dietary glycemic index is independently and positively associated with BMI [Body Mass Index]. This finding is consistent with the hypothesis that with increased glycemic index, more insulin is produced and more fat is stored, suggesting that type of carbohydrate may be related to body weight. Our data did not support the current public trend of lowering total carbohydrate intake for weight loss or of lowering glycemic load for weight loss, as suggested by other researchers.

This study refutes the suggestion that total carbohydrate consumption directly correlates with weight loss but does support the notion that the glycemic index of foods consumed correlates with weight loss. The study does not specifically distinguish between nutritive and non-nutritive carbohydrate consumption nor is it clear that any of the diets was ketogenic (a key factor for most low-carbohydrate diets).

 Journal of Nutrition and Metabolism: 2005

Yancy et al., 2005 completed a study of 28 overweight subjects with type 2 diabetes. The conclusion of the study was the following.

    The LCKD [low carbohydrate, ketogenic diet] improved glycemic control in patients with type 2 diabetes such that diabetes medications were discontinued or reduced in most participants. Because the LCKD can be very effective at lowering blood glucose, patients on diabetes medication who use this diet should be under close medical supervision or capable of adjusting their medication.

The article lends support to the argument that low carbohydrate diets can be at least a partial remedy for some forms of diabetes (and may lend support to the argument that some forms of diabetes may in fact be caused by high carbohydrate diets).

 New England Journal of Medicine: 2006

Halton et al., 2006 completed a study analyzing the long-term (20 years) health effects of low-carbohydrate diets. The study was limited to women and followed 82,802 subjects. Based on questionnaires, the study determined the correlation between the carbohydrate intake and coronary heart disease risk.

The conclusion in the article states the following.

    Our findings suggest that diets lower in carbohydrate and higher in protein and fat are not associated with increased risk of coronary heart disease in women. When vegetable sources of fat and protein are chosen, these diets may moderately reduce the risk of coronary heart disease.

This study refutes the argument that low-carbohydrate diets necessarily cause heart disease, at least in women. Perhaps more significantly, it suggests that the low-carbohydrate diet can be part of a healthy, long-term lifestyle.

Notably, this article answers the one concern raised in the conclusions by Samaha et al., 2003 (mentioned above).

 American Journal of Clinical Nutrition, 2006

Johnston et al., 2006 completed a study of 20 subjects over a 6-week period comparing ketogenic low-carbohydrate diets (i.e. very low carbohydrate) and non-ketogenic low-carbohydrate diets (i.e. moderate carbohydrate). The authors of the paper concluded the following.

    KLC and NLC diets were equally effective in reducing body weight and insulin resistance, but the KLC diet was associated with several adverse metabolic and emotional effects. The use of ketogenic diets for weight loss is not warranted.

This study suggests that ketosis has no real benefit and is potentially harmful in a diet regimen.

 International Journal of Cancer, 2006

Bravi et al., 2006 completed a study of 2301 subjects, 767 with renal cell carcinoma (cancer of the kidneys), analyzing the effects of various types of foods on the risk of developing the cancer. The authors of the paper concluded the following.

    A significant direct trend in risk was found for bread (OR = 1.94 for the highest versus the lowest intake quintile), and a modest excess of risk was observed for pasta and rice (OR = 1.29), and milk and yoghurt (OR = 1.27). Poultry (OR = 0.74), processed meat (OR = 0.64) and vegetables (OR = 0.65) were inversely associated with RCC [renal cell carcinoma] risk.

This, in effect, says that bread consumption was strongly correlated with increased risk of this carcinoma whereas the consumption of meats and vegetables decreased the risk.

 Journal of the American Medical Association, 2007

Gardner et al., 2007 studied 311 overweight women each following one of four diet plans (Atkins, Zone, LEARN, and Ornish) in 12-month trials. The authors concluded the following.

    In this study, premenopausal overweight and obese women assigned to follow the Atkins diet, which had the lowest carbohydrate intake, lost more weight and experienced more favorable overall metabolic effects at 12 months than women assigned to follow the Zone, Ornish, or LEARN diets. While questions remain about long-term effects and mechanisms, a low-carbohydrate, high-protein, high-fat diet may be considered a feasible alternative recommendation for weight loss.

The authors noted that Atkins performed favorably compared to the other diets, but stated that “It could not be determined whether the benefits were attributable specifically to the low carbohydrate intake vs. other aspects of the diet.” In terms of weight loss, all 4 groups attained ‘a modest 2% to 5% weight loss’. Throughout the study the Zone (moderately low-carb), Ornish (low-fat), and LEARN (low-fat) diets showed statistically similar weight loss to each other (the Zone actually had the worst average). The Atkins diet (very low-carb, ketogenic) performed the best for weight loss but the authors noted that the difference at 12 months was not statically significant over Ornish and LEARN. The authors noted that Atkins performed better (systolic blood pressure) or comparable (Insulin, Glucose, Lipids) to the other diets for other health indicators concluding that ‘Concerns about adverse metabolic effects of the Atkins diet were not substantiated within the 12-month study period.’

 Epilepsia, 2008

Kossoff et al., 2008 studied adult epileptic patients (as opposed to children used in other studies) following a modified Atkins diet for up to 6 months. The authors concluded the following.

    After 3 months, 47% of patients had a >50% seizure reduction, and after 6 months, 33% were similarly improved.

      When the modified Atkins diet led to seizure reduction, it was relatively quick, usually within 2 weeks.

 Meta-analytic summaries

Meta-analysis is a method to succinctly summarize and combine the results from multiple individual studies. The following meta-analyses of low carbohydrate diets are limited to randomized controlled trials that directly compare low carbohydrate diets to other diets. Some of the studies listed above are randomized controlled trials and are included in these meta-analyses.

A meta-analysis of randomized controlled trials by the Cochrane Collaboration in 2002 concluded that fat-restricted diets are no better than calorie restricted diets in achieving long term weight loss in overweight or obese people.

A more recent meta-analysis that included randomized controlled trials published after the Cochrane review found that “low-carbohydrate, non-energy-restricted diets appear to be at least as effective as low-fat, energy-restricted diets in inducing weight loss for up to 1 year. However, potential favorable changes in triglyceride and high-density lipoprotein cholesterol values should be weighed against potential unfavorable changes in low-

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 Scientific research

 

    Main article: Medical research related to low-carbohydrate diets

 

Because of the substantial controversy regarding low-carbohydrate diets and even disagreements in interpreting the results of specific studies it is difficult to objectively summarize the research in a way that reflects scientific consensus.

 

However, according to a review of the scientific data published in the Lancet, there is no proof that Atkins-style diets, are effective beyond 6 months. The review led by Arne Astrup of the Centre of Advanced Food Research at Copenhagen’s RVA University, concluded that “There is no clear evidence that Atkins-style diets are better than any others for helping people to stay slim,[and] despite the popularity and apparent success of the Atkins diet, evidence in support of its use lags behind. Although the diet appears as claimed to promote weight loss without hunger at least in the short-term, the long-term effects on health and disease prevention are unknown.”

 

The researchers concluded it was unlikely that weight-loss come through ketosis because ‘urinary traces of ketones were so low that very little energy would be used up this way. They concluded that a possible reason that participants lost weight was that the diet was so monotonous that they simply ate less; weight loss was a result of boredom. “Patients who want to try these diets should be told that, although safety cannot be guaranteed, they seem to be safe for short-term use (up to six months) as long as weight loss occurs,” the authors said.

 

Other studies have shown possible short term benefits although the long term benefit remains unknown: One study found that women eating low-carbohydrate, high-fat/protein diets had the same or slightly less risk of coronary heart disease, compared to women eating high-carbohydrate, low-fat diets. Other studies have found possible benefits to individuals with diabetes, cancer, and autism. The introduction of modern anticonvulsant drugs, however, substantially restricted its use. Interestingly, there has very recently been renewed interest in use of the diet, especially in children.

 

A study conducted in 1965 at the Oakland (California) Naval Hospital used a diet of 1000 calories per day, high in fat and limiting carbohydrates to 10 grams (40 calories) daily. Over a ten-day period, subjects on this diet lost more body fat than did a group who fasted completely. (Benoit et. al. 1965). Some subsequent studies have shown similar results. Many advocates of low-carbohydrate diets have termed this the metabolic advantage of such diets although many experts dispute whether this is truly a general phenomenon.

 

A recent study from Stanford University (2007) comparing Atkins (low-carb), Zone (moderately low-carb), LEARN (low in fat and high in carbohydrates), and Ornish (very high in carbohydrates and extremely low in fat) diets found that “of the more than 300 women in the study, those randomly assigned to follow the Atkins diet for a year not only lost more weight than the other participants, but also experienced the most benefits in terms of cholesterol and blood pressure.” “Weight loss was greater for women in the Atkins diet group compared with the other diet groups at 12 months, and mean 12-month weight loss was significantly different between the Atkins and Zone diets (P<.05). Mean 12-month weight loss was as follows: Atkins, –4.7 kg (95% confidence interval [CI], –6.3 to –3.1 kg), Zone, –1.6 kg (95% CI, –2.8 to –0.4 kg), LEARN, –2.6 kg (–3.8 to –1.3 kg), and Ornish, –2.2 kg (–3.6 to –0.8 kg). Weight loss was not statistically different among the Zone, LEARN, and Ornish groups. At 12 months, secondary outcomes for the Atkins group were comparable with or more favorable than the other diet groups.” “The amount of weight loss at 12 months relative to baseline among all groups was modest at 2% to 5% . At the end of a year, the 77 women assigned to the Atkins group had lost an average of 10.4 pounds. Those assigned to LEARN lost 5.7 pounds, the Ornish followers lost 4.8 pounds and women on the Zone lost 3.5 pounds, on average. In all four groups, however, some participants lost up to 30 pounds. It could not be determined whether the benefits were attributable specifically to the low carbohydrate intake vs. other aspects of the diet.

 

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