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 popuarlity this diet trend has continued to quietly garner attention in the medical and nutritional science communities. Practices and theoriesThe 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, and the South Beach Diet). Therefore, there is no widely accepted definition of what precisely consistutes a low-carbohydrate diet. It is important to note that the level of carbohydrate consumption defined as low-carbohydrate by medical researchers may be different than the level of carbohydrate defined by diet advisors. 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 anecdotal 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 avoids ketosis, thus causing excess energy 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.

Low-carbohydrate Diets

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 fats.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. History BeginningsIn 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 1990sIn 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).