Low Carb Diet

Low-carbohydrate diets or low carb diets are nutritional programs that advocate restricted carbohydrate consumption, based on research that ties consumption of certain carbohydrates with increased blood insulin levels, and overexposure to insulin with metabolic syndrome (the most recognized symptom of which is obesity).

Under these dietary programs, foods high in digestible carbohydrates (sugars and starches) are limited or replaced with foods containing a higher percentage of proteins, fats, and/or fiber.

The history of the low-carbohydrate diet really begins with human history. The diet of early humans (the so-called paleolithic diet) was heavily skewed toward meat and fat (some groups still dispute this but most anthropologists and biologists agree on this point).The shift toward a more carnivorous diet allowed humans to obtain calories more efficiently and to develop larger brains. The species did continue to eat plants as its ancestors had but as evolution progressed the human digestive tract could no longer derive sufficient nutrition from most of the readily accessible plants in the natural environment (bear in mind that most of the plants that humans eat today have been developed by humans through cultivation and breeding).

One of the key developments in the rise of civilization was the invention of agriculture which meant developing crops that could provide more nutrition (mostly in the form of starch) and developing cooking techniques to make the crops more edible. This innovation gradually converted human societies from almost exclusively meat-eating societies to societies that ate diets which were mixtures of meat and plants. On an evolutionary timescale, this change in diet toward eating more vegetarian diets has been very recent.

The beginning of the modern history of low-carbohydrate diets is popularly attributed to William Banting and and Dr. William Harvey (before this, though, anecdotal and holistic prescriptions, containing passages about limiting certain foods, including foods of mostly carbohydrates, have appeared throughout history). Banting was an overweight undertaker who developed hearing difficulties. He sought the help of Dr. Harvey who diagnosed his hearing difficulties as being directly related to his weight problem (his fat was pressing against his inner ear). He prescribed a diet that was very much like the low carbohydrate diets of today (which indicates this diet was, at least informally, known to be effective even at that time). Banting lost weight and his health problems disappeared. This led to Banting's publication of the book Letter on Corpulence in 1869, the first modern low-carbohydrate diet book. The mainstream thinking, though, formalized by the invention of the concept of the calorie in the late 19th century, was still that weight control was primarily a matter of controlling the amount of food consumed.

In the 1920s, Johns Hopkins Medical Center developed the high-fat, low-carbohydrate ketogenic diet for the treatment of epilepsy. This diet was found very effective in treating many forms of epilepsy. As drug therapies were later developed this treatment gradually fell out of favor (although notably it has always been one of the treatments used by Johns Hopkins).

In 1926, Dr. Clarence Lieb published a case study on anthropologist and explorer Vilhjalmur Stefansson who lived for years with the Inuit consuming a diet that was almost entirely meat and fat. Despite expecting to find serious health problems Lieb had found Stefansson (like the Inuit) to be in perfect health showing no adverse effects from his diet. Later, during World War II the medical department of E. I. DuPont hired Dr. Alfred Pennington to help address weight problems with many of the employees.After some study and experimentation Dr. Pennington determined (partly inspired by previous research at the Russel Sage Institute) that the key to weight loss was not restricting consumption overall but reducing consumption of carbohydrates and increasing consumption of proteins and fats. The diet he developed came to be known as the Dupont Diet. During the 1950's studies such as Kekwick and Pawan, 1956 and Mackarness et al., 1958 continued to demonstrate the effectiveness of carbohydrate restriction and the ineffectiveness of calorie restriction.

Mainstream science still favored the idea of calorie restriction. In addition, research by Ancel Keys starting in the 1950s led ultimately to the publication of Seven countries: a multivariate analysis of death and coronary heart disease in 1980 which linked consumption of cholesterol and saturated fats to heart disease. This research led to the contemporary low-fat diet trend and discouraged research into low-carbohydrate diets. It should be noted that Keys' theory was not universally accepted when published originally, Dr. George Mann being a noted detractor.

Despite this low-carbohydrate diets such as the Air Force Diet (referred to by some as the first real "low carb" diet) and the Drinking Man's Diethad brief periods of popularity in the 1960s. In 1972, Dr. Robert Atkins published Dr. Atkins Diet Revolution which advocated a low-carbohydrate diet he had successfully used in treating thousands of patients in the 1960s. Like its predecessors the book met with some success but, because of research at that time demonstrating risk factors associated with excess fat and protein, it was very 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 annectdotal evidence. Dr. Atkins nevertheless continued to develop his theories and gain followers. During the 1980s and 1990s the obesity epidemic in the United States blossomed in spite of the popularity of low-fat diets thereby leading many doctors to question the efficacy of this approach. The concept of the glycemic index was invented in 1981 by Dr. David Jenkins.This and subsequent research demonstrated that many complex carbohydrates can be as harmful as sugars. In the 1990s Dr. Atkins published Dr. Atkins New Diet Revolution and other doctors (and later celebrities and health gurus) began to publish books based on the same principles. This can be 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 many 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 vehemently 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 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. It is also valuable to note that most of major medical groups have acknowledged at least that the low-carbohydrate diet is effective in the short-term. 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 study). After 2004 the popularity of this diet trend began to wane significantly although it still remains quite popular.

 Practices and Theories

The term low-carbohydrate diet today is most strongly associated with the Atkins Diet. However, there is an array of other diets that share to varying degrees the same principles (e.g. the Zone Diet, the Protein Power Lifeplan, the South Beach Diet). As mentioned above there have been diet recommendations that follow the same principles in existence since before the twentieth century. As such it is difficult to summarize all of these diets and draw a sharp distinction between these and other diets. There is, therefore, no widely accepted definition of what precisely consistutes a low-carbohydrate diet. For the purposes of this discussion, we focus on diets that reduce (nutritive) carbohydrate intake sufficiently to dramatically reduce or eliminate insulin production in the body and to encourage ketosis (production of ketones to be used as energy in place of glucose).

Although originally low-carbohydrate diets were created based on annecdotal evidence of their effectiveness, today there is a much greater theoretical basis on which these diets rest. The key scientific principle which forms the basis for these diets is the relationship between consumption of carbohydrates and their effects on blood sugar (i.e. blood glucose) and hormone production. Blood sugar levels in the human body must be maintained in a fairly narrow range to maintain health. The two primary hormones related to regulating blood sugar levels, produced in the pancreas, are insulin, which lowers blood sugar levels, and glucagon, which raises blood sugar levels. In general, most western diets (and many others) are sufficiently high in nutritive carbohydrates that virtually every meal causes substantial insulin production and shuts down ketosis which causes excess calories in the diet to be stored as fat (discussed in the next section). By contrast, low-carbohydrate diets, or more properly, diets that are very low in nutritive carbohydrates, discourage insulin production and tend to cause ketosis which, according to some, can actually cause excess dietary calories as well as excess body fat to be eliminated from the body. Although these diets remain controversial there are clinical studies related to their effectiveness.

Low-carbohydrate diet advocates in general recommend reducing nutritive carbohydrates (commonly referred to as "net carbs," i.e. total carbohydrates reduced by the non-nutritive carbohydrates) to very low levels. This means sharply reducing comsumption of desserts, breads, pastas, potatoes, rice, and other sweet or starchy foods. Some recommend levels as low as 20-30 grams of "net carbs" per day, at least in the early stages of dieting (for comparison, a single slice of white bread may contain 15-25 grams of carbohydrate, almost entirely starch). The diets often differ in the specific amount of carbohydrates allowed, whether certain types of foods are preferred, whether occasional exceptions are allowed, etc. Generally they all agree that processed sugar should be eliminated, or at the very least greatly reduced, and similarly generally discourage heavily processed grains (white bread, etc.). They vary greatly in their recommendations as to the amount of fat allowed in the diet although the most popular versions today (including Atkins) generally recommend at most moderate fat intake.

As a related note, there is a set of diets known as low-glycemic-index diets (low-GI diets) or low-glycemic-load diets (low-GL diets), in particular the Low GI Diet by Brand-Miller et al.. In reality, low-carbohydrate diets are, literally speaking, low-GL diets (and vice versa) in that they specifically limit what contributes to the glycemic load in foods. In practice, though, the diets that call themselves low-GI/low-GL diets differ from those calling themselves low-carbohydrate diets in the following ways.

1) Low-carbohydrate diets treat all nutritive carbohydrates as having the same effect on metabolism and generally assume that their effect is independent of other nutrients in food. Low-GI/low-GL diets base their recommendations on the actual measured metabolic (glycemic) effects of the foods eaten.

2) As a practical matter, the so-called low-GI/low-GL diets generally do not recommend diets with glycemic loads low enough to minimize insulin production and induce ketosis whereas the so-called low-carbohydrate diets generally do.

Another related diet type, the low-insulin-index diet, is very similar except that it is based on measurements of direct insulemic responses to food rather than glycemic response. Although the diet recommendations mostly involve lowering nutritive carbohydrates, there are some low-carbohydrate foods that are discouraged as well (e.g. beef).

 Ketosis and Insulin Synthesis: What is Normal?

At the heart of the debate about most low carbohydrate diets are fundamental questions about what is a "normal" diet and how the human body is designed to operate. These questions can be summarized as follows. Nutritive carbohydrates (starches and sugars) in the diet tend to break down very easily into glucose in the bloodstream (blood sugar) when consumed. Glucose in the blood is used by the cells in the body for energy for their basic function. Excessive amounts of glucose in the blood are toxic to the human body (the reason diabetes causes such serious health problems). In general, unless a meal is very low in starches and sugars the level of glucose will tend to rise to potentially dangerous levels. When this occurs, the pancreas automatically produces insulin to cause the liver to convert glucose into glycogen (glycogenesis) and triglycerides (which can become body fat), thus reducing the blood sugars to safe levels. Diets with a high starch/sugar content, therefore, cause sharp spikes in insulin production. As such the blood sugar levels are highly variable with every meal.

By contrast, if the diet is very low in starches and sugars (low-carbohydrate diets) the blood sugar level can fall so low that there is insufficient glucose to fuel the cells in the body. This state causes the pancreas to produce glucagon. Glucagon causes the conversion of stored glycogen to glucose and, once the glycogen stores are exhausted, causes the liver to synthesize ketones (ketosis) and glucose (gluconeogenesis) from fats and proteins. Most cells in the body can use ketones for energy instead of glucose and, since ketones are easier to produce, only a small amount of glucose is created (in other words, ketosis is the more significant process in this case). Because diets low in starches and sugars do not tend to directly affect blood sugar levels significantly, meals tend to have little direct affect on insulin levels (and so such diets tend to discourage insulin production in general).

The diets of most people in modern, so-called western nations, especially the United States contain significant amounts of starches (and, frequently, significant amounts of sugars). As such, the metabolisms of most westerners tend to operate outside of ketosis and tend to involve significant insulin production. This has been regarded by medical science in the last century as being "normal." Ketosis has generally been regarded as a dangerous (potentially life-threatening) state which unnecessarily stresses the liver and causes destruction of muscle tissues. The view that has been developed is that getting calories more from protein than carbohydrates causes liver damage and that getting calories more from fats than carbohydrates causes heart disease. This view is still the view of the majority in the medical and nutritional science communities.

Most advocates of low-carbohydrate diets (specifically those that recommend diets similar to the Atkins Diet) argue that this metabolic state (using primarily blood glucose for energy) is not normal at all and that the human body is, in fact, designed to function primarily in ketosis. They argue that high insulin levels can, in fact, cause many health problems, most significantly, fat storage and weight gain. They argue that the purported dangers of ketosis are unsubstantiated (some of the arguments against ketosis result from confusion between ketosis and ketoacidosis which is a related but very different process). They also argue that fat in the diet only contributes to heart disease in the presence of high insulin levels and that if the diet is instead adjusted to induce ketosis, fat and cholesterol in the diet are not a major concern (although most do not advocate unrestricted fat intake and do advocate avoiding trans fat). Further, whereas insulin in the bloodstream causes storage of calories, when the body is in ketosis, excess ketones (which contain excess calories) are excreted in the urine and the breath. Many argue, on this basis, that the ketosis offers a so-called metabolic advantage in that the body automatically eliminates calories that it does not need even with a high-calorie diet (this argument has not yet been explicitly demonstrated by any clinical studies).

This debate is on-going and no general consensus exists at this time.

The evolutionary argument

The Paleolithic diet did not include grains, starches, and refined sugar, and the human body has not evolved significantly since the time of the Neolithic Revolution, implying that their consumption should still be avoided today and causes undesired and largely unknown effects. Specifically, they cause the body to produce excess amounts of the hormone insulin, which tells the body to store rather than burn fat, hence causing obesity and its complications (heart disease, cancer, Type 2 diabetes). Humans evolved to eat a diet which consisted mainly of meat and that the current "epidemic" of obesity is due to the popular assumption, reinforced by the food industry and the new field of dietary medicine, that the low-fat approach is healthier.

Supporters claim the exclusive focus on reducing fat is oversimplified, and that low-fat diets are not automatically healthy ones. They claim that the western world is not suffering from a collective failure of will to exercise, but has been encouraged to eat more carbohydrates, which in turn stimulate appetite and more eating. Some go so far as to suggest that if the human body were truly as fragile and susceptible to illness due to small variations in diet as many doctors and dieticians have been suggesting, the species could never have survived its more primitive days. They argue that the fact that industrialized nations (notably the U.S.) are showing such an epidemic of health problems indicates that some fundamental and important aspect of the diet among these people is drastically different from early humans (and indeed the intake of sugars and starches certainly qualifies as a big difference).

The recent rise in western obesity rates has coincided with a widespread belief in low-fat, high-carbohydrate as a healthy way of eating. By contrast, traditional high-fat French cooking has led to a much lower incidence of obesity, morbid obesity and chronic heart disease than the high-sugar American diet, despite overall energy intake and exercise levels being the same.

 Favorable studies

Advocates point to scientific trials demonstrating the efficacy and safety of low carb diets. Several independent clinical trials have shown that low carb diets can be successfully used to lose weight. These trials found that, in the short term, risk factors for heart disease and Type 2 diabetes — such as blood serum cholesterol and insulin levels — tended to improve in spite of increased consumption of saturated fat and cholesterol. The trials were of short duration, and were not able to assess the long-term health effects of the diet.

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.. Some advocates of low-carbohydrate diets have termed this the metabolic advantage of such diets.

 Arguments against low-carbohydrate diets

In 2004, the Canadian government ruled that foods sold in Canada could not be marketed with reduced or eliminated carbohydrate content as a selling point because reduced carbohydrate content was not determined to be a health benefit, and that existing "low carb" and "no carb" packaging would have to be phased out by 2006. This is not an "argument against low carb diets" but is instead marketing regulatory action intended to avoid abuses. Low-fat and low-salt labelling continues to be allowed under these regulations.

 Side effects

Critics contend that low carbohydrate diets are not without harmful side effects. The lowered intake of dietary fiber that often accompanies dramatically reduced carbohydrate intake can result in constipation if not supplemented. For example, this has been a criticism of the Induction stage of the Atkins diet (note that today the Atkins diet is more clear about recommending a fiber supplement during Induction).

Replacement of calories from carbohydrates with proteins may result in overload on the renal system and increase the risk of arthritis. Increased consumption of animal-based products may lead into high consumption of saturated fat and cholesterol, which many authorities believe will increase the risk of heart disease. Moreover, it has been hypothesized that the kidneys can become overworked and that a related change in blood acidity can lead to bone loss One of the telltale signs of diet consisting on too little fat and too much protein is strong stench of ammonia in urine.

Cutting out carbohydrates may mean missing out on vital nutrients from healthy carbohydrate foods which should be part of any well-balanced diet, especially those from fruits, vegetables and whole grains. If you’re considering a low-carb diet for weight loss, remember to make sure you get enough nutrients. Most low-carb diets emphasize intake of carbohydrates as fresh vegetables instead of cereals and bakery products.

 Environmental impact

Since changes in habit of 6 billion people over a long term totals up to a huge amount of food, it may be important to growth in global population over the last few centuries was only possible because of grain crops. Poor quality pasture has traditionally been fit only for raising livestock and that it has been turned to grain production only through massive government subsidies, fertilizers and pesticides.

Raising livestock instead of eating vegetable food has poor energy efficiency - around 3% of the intake of energy consumed by livestock can be employed from animal-based food. However, meat and dairy products are enriched on proteins and other nutrients. It is often also more economical to raise cattle instead of attempting to harness the area on grain production, especially when the climate conditions strongly disfavour grain and human consumable vegetables. Moreover, pasture needs less fertilization, pesticides and cultivation than grain fields and their environmental impact is likely to be less than same area of grain fields.

It must be pointed out too that parts of the above argument imply that a low-carbohydrate diet must be high in meat consumption, especially ruminants. Although certainly this is common among many practitioners of the low-carbohydrate diets few if any mainstream guides for this diet say that this is a requirement (e.g. a diet which concentrates on soy and/or fish can be quite low in carbohydrates, and fat for that matter, without requiring raising more land animals).

 Food industry response

Food producers have ascribed a commercial impact to the growing popularity of low-carbohydrate diets in recent years. For example, in May 2004, New World Pasta filed for bankruptcy protection, claiming that low-carbohydrate diets were reducing demand for pasta. In the same month, Krispy Kreme Doughnuts warned investors that its earnings would be below projections, and blamed low-carbohydrate diets on reduced demand for its products.

Other producers have taken advantage of the trend. In response to consumer demand for low-carb foods, the food industry has been marketing low-carb products in recent years and restaurants are increasingly offering low carb menus. These items typically replace carbohydrate-laden wheat flour with high-protein soy flour and replace sugar with artificial sweeteners such as sucralose and sugar alcohols.

The low-carbohydrate diet trend has generated a great deal of controversy which has spawned many myths and misconceptions.

 Meat, vegetable, and fiber content of the diet

Some practitioners of low-carbohydrate diets may choose to eat high proportions of beef and sausage in their diets and, indeed, most low-carbohydrate diet experts (though not all) allow for more liberal consumption of fatty meats than some other diets. However, most of the main low-carbohydrate diets tend to encourage consumption of poultry and fish and similar types of meat in higher proportions than beef and more fatty pork products. It is, in fact, worth noting that a vegetarian diet is possible although this generally requires soybean products (e.g. tofu) as staples of the diet (other types of beans generally have too much starch to be acceptable as primary sources of protein).

A low-carbohydrate diet can contain vegetables, although many of the most popular vegetables in English-speaking countries are less suitable due to their high starch and/or sugar content (e.g. potatoes, corn, rice, etc.). However, there is a wide variety of vegetables that are low in sugar and starch (e.g. spinach, cauliflower, broccoli, green beans). Indeed most of the major low-carbohydrate guides strongly advocate balancing one's diet with a healthy proportion of vegetables.

Many low-carbohydrate diets closely limit fruits in general because most fruits have a significant sugar content. These diets typically, though, do not outlaw fruits entirely. As a general rule, nutrients available in sugar-rich fruits are readily available in other vegetables as well so reduction of fruit consumption does not have to imply limiting consumption of important nutrients.

The older (pre-Atkins) low-carbohydrate diet guides focused on refined sugars and starches as the primary concerns, not carbohydrates in general. When Dr. Atkins' Diet Revolution was first published in 1972 the book demonized all carbohydrates as unhealthy including fiber. Since that time, especially as the concept of the glycemic index was defined and developed, it has been recognized that fiber and some other carbohydrates such as sugar alcohols are not metabolized by the human body and, therefore, do not contribute to blood sugar and do not significantly trigger insulin production. Furthermore the health benefits of fiber have been recognized leading Atkins and others to modify their recommendations to distinguish between "bad carbs" (starch and sugar) and other carbohydrates (e.g. fiber). This has lead to the term "net carbs", another name for "bad carbs", so-called because it is typically calculated as the total amount of carbohydrates reduced by the amount of carbohydrates that are not metabolized. As such, the term "low-carbohydrate" today is really somewhat of a misnomer since most of these diets no longer strictly advocate eliminating all types of carbohydrates.

 Water-related weight loss

In the first week or two of a low-carbohydrate diet a great deal of the weight loss comes from eliminating water retained in the body (many doctors say that the presence of high levels of insulin in the blood causes unnecessary water retention in the body). However, this is a short-term effect and is entirely separate from the general weight loss that these diets can produce through eliminating excess body fat.

 Exercise

Arguments have been made that low-carbohydrate diets inherently cause weakness or fatigue giving rise to the assumption by some that low-carbohydrate dieting cannot involve an exercise regimen. Advocates of low-carbohydrate diets generally dispute any suggestion that such diets cause weakness or exhaustion (except in the first few days) and indeed most highly recommend exercise as part of a healthy lifestyle

 Carbohydrate intake today and in the past

The human diet has changed significantly through history and, as such, assertions that the diets that most humans eat today are representative of the diets humans have always eaten are, at best, exaggerations. It is well established that just in the twentieth century, the consumption of sugar per capita in the U.S. and the U.K. has steadily and dramatically increased. Starch consumption has increased as well. Moreover it is well known that early humans ate diets that were heavily meat-based and that the shift toward high levels of starch and sugar consumption occurred much later. The current trend toward very high-carbohydrate, low-fat diets in the West is, in reality, a quite recent trend owing in large part to the research of Ancel Keys.

 Micronutrients and vitamins

The major low-carbohydrate diet guides generally recommend multi-vitamin and mineral supplements as part of the diet regimen which may lead some to believe that these diets are nutritionally deficient. The primary reason for this recommendation is that if the switch from a high-carbohydrate to a low-carbohydrate, ketogenic diet is rapid, the body can temporarily go through a period of adjustment during which the body may require extra vitamins and minerals (the reasons have to do with the body's releasing excess fluids that were stored during high-carbohydrate eating). In other words, the body goes through a temporary "shock" if the diet is changed to low-carbohydrate dieting quickly just as it would changing to a high-carbohydrate diet quickly. This does not, in and of itself, indicate that either type of diet is nutritionally deficient.

It should be noted that, contrary to the recommendations of most diet guides, some individuals choose to avoid vegetables altogether in order to minimize carbohydrates. It is more likely  that such a diet could be nutritionally deficient (some would dispute this based on cases like Vilhjalmur Stefansson). Regardless of the truth in that regard, the choices of some individuals should not be confused with the recommendations of major experts and guides.

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