Low-carbohydrate diet
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'''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]]s.
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 Nutritional Approach|Atkins diet]],<ref>[http://women.webmd.com/guide/high-protein-low-carbohydrate-diets Weight Loss: High Protein, Low Carbohydrate Diets]</ref><ref>Stefanov, Sebastien: ''[http://www.askmen.com/sports/foodcourt_60/63_eating_well.html Do Low-Carb Diets Work?]'', AskMen.com, </ref><ref>Hanlon, Kathie: ''[http://www.vanderbilt.edu/AnS/psychology/health_psychology/carbs.htm The Low-Down on Low-Carbohydrate Diets]'', Vanderbuilt University, 25 April, 1997</ref> but some sources consider less restrictive variants to be ''low-carbohydrate'' as well.<ref>Dolson, Laura: ''[http://lowcarbdiets.about.com/od/faq/f/lcdfaq1.htm What is a Low Carb Diet?]'', About.com: Low Carb Diets, retrieved 11 March 2008</ref>
Apart from [[obesity]] low-carbohydrate diets are often discussed as treatments for some other conditions, most notably [[diabetes]]<ref>''[http://health.usnews.com/usnews/health/healthday/071228/diabetes-group-backs-low-carb-diets.htm Diabetes Group Backs Low-Carb Diets]'', U.S. News and World Report, 28 Dec. 2007</ref><ref>Kossoff, Eric: ''[http://www.epilepsy.com/epilepsy/keto_news_march07 Do ketogenic diets work for adults with epilepsy? Yes!]'', Epilepsy.com, updated 22 Feb 2008</ref><ref>Newman, Bettina: ''[http://www.prevention.com/cda/article/the-low-carb-diabetes-plan-that-works/548c68f271903110VgnVCM10000013281eac____/weight.loss/diets/other.popular.diets/low.carb.diets/0/2]'', Prevention Magazine, 21 September 2004</ref> and [[epilepsy]],<ref>Schachter, Steven C.: ''[http://www.epilepsy.com/epilepsy/treatment_atkins_diet]'', Epilepsy.com, 15 March 2006</ref><ref>Brownlee, Christen: ''[http://www.hopkinsmedicine.org/Press_releases/2008/01_28_08.html MODIFIED ATKINS DIET CAN CUT EPILEPTIC SEIZURES IN ADULTS]'', Press Release, Johns Hopkins Medicine, 28 January 2008</ref><ref>Kleffman, Sandy: ''[http://findarticles.com/p/articles/mi_qn4176/is_20080130/ai_n21218890 High-fat, low-carb diet miracle for epileptic kids]'', Oakland Tribune, 30 Jan 2008</ref> although these treatments still remain controversial and lack widespread support.
==History==
===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.<ref name=Banting>{{cite book |url=http://2020ok.com/books/25/letter-on-corpulence-addressed-to-the-public-19925.htm |title = Letter On Corpulence, Addressed To The Public |author=William Banting |publisher= Harrison |location=London, England |date=1869 |edition=4th |accessdate=2008-01-02}}</ref> His booklet was widely read, so much so that some people used the term "Banting" for the activity usually called "dieting."<ref name=Groves>{{cite web| url=http://www.westonaprice.org/knowyourfats/banting.html |title=William Banting Father of the Low-Carbohydrate Diet |author=Barry Groves |publisher= The [[Weston A. Price Foundation]] |date=2002}}</ref>.
In 1967, Dr. Irwin Stillman published [[Stillman diet|The Doctor's Quick Weight Loss Diet]]. The "Stillman Diet" is a [[high protein diet|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]].<ref>[http://findarticles.com/p/articles/mi_m1608/is_6_19/ai_102140891 1967: the Stillman diet - History Of Diets, Part 12 - protein diet] Men's Fitness. June 2003</ref> Other low-carbohydrate diets in the 1960s included ''Air Force Diet''<ref>Air Force Diet. Toronto, Canada, Air Force Diet Publishers, 1960.</ref> and the ''Drinking Man’s Diet''.<ref>Gardner Jameson and Elliot Williams (1964) ''The Drinking Man’s Diet''. San Francisco: Cameron. (2004) Revised Ed. ISBN 978-0918684653. See also Alan Farnham (2004) “[http://www.forbes.com/2004/04/21/cz_af_0421feat.html The Drinking Man’s Diet]”, Forbes.com.</ref> Austrian physician Dr Wolfgang Lutz published his book 'Leben Ohne Brot' (Life Without Bread) in 1967.<ref>Lutz, Wolfgang; Allan, C.B. ''Life Without Bread ''. McGraw-Hill; 2000. ISBN 978-0658001703. English language, 1st Ed.</ref> However it was hardly noticed in the English speaking world.
In 1972, [[Robert Atkins|Dr. Robert Atkins]] published [[Atkins Diet|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 [[Journal of the American Medical Association|JAMA]]).<ref name="The History of the Atkins Diet‚ A Revolutionary Lifestyle">The History of the Atkins Diet‚ A Revolutionary Lifestyle[http://www.e-clipse.com/articles_history.htm]</ref> 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.<ref>''[http://www.atkinsexposed.org/atkins/75/American_Medical_Association.htm A critique of low-carbohydrate ketogenic weight reduction regimens. A review of Dr. Atkins' diet revolution.]'', Journal of the American Medical Association, 1973</ref> 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.<ref>DJ Jenkins et al (1981) "Glycemic index of foods: a physiological basis for carbohydrate exchange." Am J Clin Nutr 34; 362-366</ref>
===Low-carb diets since the 1990s===
In the 1990s Dr. Atkins published [[Atkins Diet|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."<ref name="PBS News Hour: Low Carb Craze">PBS News Hour: Low Carb Craze[http://www.pbs.org/newshour/bb/health/jan-june04/carb_04-23.html]</ref> 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<ref>Americans Look for Health on the Menu:
Survey finds nutrition plays increasing role in dining-out choices [http://healthlink.uhseast.com/healthyliving/nutrition/sept06americans.htm]</ref>) 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]]<ref name="Low-Carb Diets Trim Krispy Kreme's Profit Line">Low-Carb Diets Trim Krispy Kreme's Profit Line[http://www.npr.org/templates/story/story.php?storyId=1968804]</ref>). This was in spite of the fact that the mainstream medical community continued to denounce low-carbohydrate diets as being a dangerous trend.<ref>American Heart Association Statement on High-Protein, Low-Carbohydrate Diet Study Presented at Scientific Sessions[http://www.americanheart.org/presenter.jhtml?identifier=3006728]</ref><ref>Research Reaffirms Role of Complex Carbohydrates in Weight Loss[http://www.aicr.org/site/News2?abbr=pr_&page=NewsArticle&id=7663]</ref><ref>The American Kidney Fund: American Kidney Fund Warns About Impact of High-Protein Diets on Kidney Health: 25 April 2002</ref> 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)<ref name="The Use and Misuse of Fruit Juice in Pediatrics">The Use and Misuse of Fruit Juice in Pediatrics[http://aappolicy.aappublications.org/cgi/content/full/pediatrics;107/5/1210]</ref>. The low-carbohydrate advocates did some adjustments of their own increasingly advocating controlling fat and eliminating [[trans fat]].<ref name="eat less fat">BBC (January 19, 2004) [http://news.bbc.co.uk/2/hi/health/3408931.stm Atkins diet boss: 'Eat less fat']. ''BBC News''. Retrieved on [[September 12]], [[2007]].</ref><ref>''[http://books.google.com/books?id=oFRIIFfeOfwC&pg=PA23&dq=atkins+%22trans+fat%22&sig=r6FR2KCieaWG_bUXcwyjasbjorc The Atkins Essentials: A Two-Week Program to Jump-start Your Low Carb Lifestyle]'', ISBN-13: 978-0060598389, page 23</ref> 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]]).<ref>Sears, Barry; Lawren, Bill: ''[http://books.google.com/books?id=fewLJwAACAAJ&dq=%22The+zone%22 Enter the Zone]'', Regan Books, 1995, 352 pp, ISBN 0060391502</ref><ref>Brand-Miller, Jennie; Foster-Powell, Kaye; McMillan-Price, Joanna: ''[http://books.google.com/books?id=cUz1wJMlGDkC&printsec=frontcover&dq=%22The+low+GI+diet+Revolution%22&sig=MEWxsMmVc_49o_V9wY5x3AouzeM#PPR3,M1 The Low GI Diet Revolution: The Definitive Science-Based Weight Loss Plan]'', Marlowe & Company, 30 November 2004, 336 pp, ISBN-13: 978-1569244135</ref> 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 [[New England Journal of Medicine|NEJM]] paper by Halton et al. describing a [http://content.nejm.org/cgi/content/abstract/355/19/1991 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.<ref>''[http://health.usnews.com/usnews/health/healthday/071228/diabetes-group-backs-low-carb-diets.htm Diabetes Group Backs Low-Carb Diets]'', U.S. News and World Report, 28 Dec. 2007</ref><ref>Kossoff, Eric: ''[http://www.epilepsy.com/epilepsy/keto_news_march07 Do ketogenic diets work for adults with epilepsy? Yes!]'', Epilepsy.com, updated 22 Feb 2008</ref><ref>Rosen, Evan David: ''[http://www.defeatdiabetes.org/Articles/diet030618.htm Weighing In On the Low Carb Diet Controversy]'', Defeat Diabetes Foundation, 18 June 2003</ref><ref>Burros, Marian: ''[http://query.nytimes.com/gst/fullpage.html?res=9D06EFDE1239F932A15752C0A9629C8B63&sec=&spon=&pagewanted=all EATING WELL; The Post-Atkins Low Carb Diet]'', The New York Times, 21 January 2004</ref>
==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|Zone Diet]], the Protein Power Lifeplan, and the [[South Beach diet|South Beach Diet]]).<ref>Dolson, Laura: ''[http://lowcarbdiets.about.com/od/populardietplans/Popular_Low_Carb_Diet_Plans.htm Popular Low Carb Diet Plans]'', About.com: Low Carb Diets, retrieved 12 March 2008</ref> 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.<ref>Gittleman, Ann Louise: ''[http://books.google.com/books?id=jk2VJbUyEasC&pg=PA53&lpg=PA53&dq=%22protein+power%22+chapter&source=web&ots=ddPrO-HmU5&sig=ftu-PZRcYvLbVLaVea6vpy3pjsw&hl=en#PPA53,M1 Eat Fat, Lose Weight]'', Chapter 5, McGraw Hill, 11 March 1999, ISBN 087983966X / 9780879839666</ref><ref>Eades, Michael R.; Eades, Mary Dan: ''Protein Power'', Chapter 1, Bantam Books, 1999, ISBN 0553380788</ref> 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.<ref>''[http://www.endocrineweb.com/insulin.html Normal Regulation of Blood Glucose]'', EndocrineWeb.com, retrieved 12 March 2008</ref> In general, most [[western world|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. Some researchers suggest that this causes excess dietary energy and body fat to be eliminated from the body. However, a review study of the scientific data published in the Lancet concluded that in the case of Atkins that there was no proof that the diet was effective beyond six months, and that it was unlikely that weight loss came through ketosis because 'urinary traces of ketones were so low that very little energy would be used up this way'. <ref>
[http://www.abc.net.au/news/newsitems/200409/s1192092.htm Study questions long-term Atkins effects - ABC News, 4 Sept 2004]</ref> Other studies have shown that small amounts of weight loss (approx. 1lb every 1 or 2 months) are achievable with such diets.<ref>Gardner CD, Kiazand A, Alhassan S, Kim S, Stafford RS, Balise RR, Kraemer HC, and King AC (2007), [http://jama.ama-assn.org/cgi/content/full/297/9/969 Comparison of the Atkins, Zone, Ornish, and LEARN Diets for Change in Weight and Related Risk Factors Among Overweight Premenopausal Women: The A TO Z Weight Loss Study: A Randomized Trial]. ''Journal of the American Medical Association'', Volume 297, Issue 9, Pages 969-977. PMID 17341711. Retrieved on [[September 13]], [[2007]].</ref>
Low-carbohydrate diet advocates in general recommend reducing nutritive carbohydrates (commonly referred to as "net carbs," i.e. grams of total carbohydrates reduced by the non-nutritive carbohydrates)<ref>Dolson, Laura: ''[http://lowcarbdiets.about.com/od/products/a/netcarbs.htm What Are Net Carbs?]'', About.com: Low Carb Diets, retrieved 13 March 2008</ref><ref>''[http://www.atkins.com/company/press-release/breakthrough-science-advances-atkins-net-carb-labeling-claims-on-food-products/?searchterm=net%20carbs BREAKTHROUGH SCIENCE ADVANCES ATKINS LABELING CLAIMS ON FOOD PRODUCTS]'', Press Release, Atkins Nutritional, 6 October 2004, New York, New York</ref> to very low levels. This means sharply reducing consumption 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<ref>''[http://www.atkins.com/articles/atkins-phases/phase-one/phase-1-induction/ Phase 1: Induction]'', Atkins.com, retrieved 14 March 2008</ref> (for comparison, a single slice of white bread typically contains 15 grams of carbohydrate, almost entirely starch). By contrast, more standard nutrition guides typically recommend consumption levels in the neighborhood of 225-325 grams of carbohydrate per day (based on a 2000 calorie a day diet).<ref>''[http://www.health.gov/dietaryguidelines/dga2005/document/default.htm Dietary Guidelines for Americans]'', Chapter 7, U.S. Department of Health and Human Services, 2005</ref><ref>''[http://www.ific.org/nutrition/sugars/index.cfm?renderforprint=1 Nutrition: Carbohydrates & Sugars]'', International Food Information Council, November 2006</ref> Low-carbohydrate 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 Diet|Atkins]]) generally recommend at most a moderate fat intake.
As a related note, there is a set of diets known as [[glycemic index|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.<ref>Brand-Miller et al (2005). The Low GI Diet Revolution: The Definitive Science-based Weight Loss Plan. Marlowe & Company. New York, NY</ref> 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, "low-GI"/"low-GL" diets differ from "low-carb" diets in the following ways. First, 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. Second, as a practical matter, low-GI/low-GL diets generally do not recommend diets with glycemic loads low enough to minimize insulin production and induce ketosis, whereas low-carbohydrate diets generally do.
Another related diet type, the [[Insulin index|low-insulin-index diet]], is very similar except that it is based on measurements of direct insulemic responses (i.e. the amount of [[insulin]] in the bloodstream) to food rather than glycemic response (the amount of [[glucose]] in the bloodstream). Although the diet recommendations mostly involve lowering nutritive carbohydrates, there are some low-carbohydrate foods that are discouraged as well (e.g. beef).<ref>{{cite journal | author=SH Holt, JC Miller and P Petocz | title=An insulin index of foods: the insulin demand generated by 1000-kJ portions of common foods | journal=American Journal of Clinical Nutrition | year=1997 | volume=66 | url=http://www.ajcn.org/cgi/content/abstract/66/5/1264 | pages=1264–1276 | pmid=9356547}}</ref>
In contrast to these diets, 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 [[food energy|dietary energy]] from carbohydrates.<ref>Food and Nutrition Board (2002/2005). ''[http://newton.nap.edu/books/0309085373/html Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids]''. Washington, DC: The [[National Academies Press]]. Page [http://newton.nap.edu/books/0309085373/html/769.html 769]. ISBN 0-309-08537-3</ref> 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).<ref>Joint WHO/FAO expert consultation (2003). ''[http://www.who.int/hpr/NPH/docs/who_fao_expert_report.pdf Diet, Nutrition and the Prevention of Chronic Diseases]'' ([[Portable Document Format|PDF]]). Geneva: [[World Health Organization]]. Pages 55-56. ISBN 92-4-120916-X</ref>
== 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 supposed 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.<ref>Bowen, R.: ''[http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/pancreas/index.html The Endocrine Pancreas]'', Colorado State University: Hypertexts for Biomedical Sciences, 8 December 2002</ref> 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]].<ref>Carr, Timothy P.: ''[http://books.google.com/books?id=z3Qp2z2ByV4C&pg=PA194&dq=glucagon+glycogen+ketone&sig=HWX132ylv-Es3A_LUPKWdxD-OHc#PPA72,M1 Discovering Nutrition]'', Chapter 7, Blackwell Publishing, October 2002, ISBN: 9780632045648</ref> Glucagon causes the conversion of stored glycogen to glucose and, once the glycogen stores are exhausted, causes the liver to synthesize [[ketone bodies|ketones]] ([[ketosis]]) and glucose ([[gluconeogenesis]]) from fats and proteins, respectively. 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 effect on insulin levels (and so such diets tend to discourage insulin production in general).
The diets of most people in modern, so-called [[western world|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 energy more from protein than carbohydrates causes liver damage and that getting energy more from fats than carbohydrates causes [[coronary heart disease|heart disease]] and other health problems. This view is still the view of the majority in the medical and nutritional science communities.<ref>''[http://www.americanheart.org/presenter.jhtml?identifier=11234 High-Protein Diets]'', American Heart Association, 14 March 2008</ref><ref>''[http://www.cancer.org/docroot/SPC/content/SPC_1_A_Low_Carb_Diet_to_Prevent_Cancer.asp
Weighing In on Low-Carb Diets]'', The American Cancer Society, retrieved 12 March 2008</ref><ref>Karra, Cindy: ''[http://www.shapeup.org/about/arch_pr/122903.php Shape Up America! Reveals The Truth About Dieters]'', Shape Up America! (by former U.S. Surgeon General C. Everett Koop), 29 December 2003</ref>
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, supposed to function primarily in ketosis.<ref>Eades, Michael R.: ''[http://www.proteinpower.com/drmike/intermittent-fasting/protein-power-verses-intermittent-fasting/ http://www.proteinpower.com/drmike/intermittent-fasting/protein-power-verses-intermittent-fasting/]'', ProteinPower.com, 19 September 2006</ref><ref>Morrison, Katharine: ''[http://www.dsolve.com/component/option,com_docman/task,doc_download/gid,13/Itemid,27/ Dietary Carbohydrate, Protein and Fat for People With Glucose Metabolism Disorders. Just What is Optimal?]'', D-Solve: Low Carb & Low Insulin Diabetes Management, February 2005</ref> 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).<ref>Dolson, Laura: ''[http://lowcarbdiets.about.com/od/faq/f/whatisketosis.htm What is Ketosis?]'', About.com: Low Carb Diets, retrieved 13 March 2008</ref> 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 food energy, when the body is in ketosis, excess ketones (which contain excess energy) are excreted in the urine and the breath.<ref>Bowden, Jonny: ''[http://books.google.com/books?id=U1Ju61Vgd8AC&pg=PA62&lpg=PA62&dq=ketones+excrete+urine+breath+%22low+carb%22&source=web&ots=fldtKP83V9&sig=cnOxqVPgK0WL3BlBH0YWwwfVd2c&hl=en#PPP11,M1 Living the Low Carb Life: From Atkins to the Zone]'', Chapter 2, Sterling Publishing, February 2004, ISBN-13: 9781402713989, 352pp</ref>
This debate is on-going and no consensus currently exists.
==Scientific research==
{{main|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.<ref>Taubes, Gary: ''[http://query.nytimes.com/gst/fullpage.html?res=9F04E2D61F3EF934A35754C0A9649C8B63 What if It's All Been a Big Fat Lie?]'', New York Times, Friday, February 15, 2008</ref><ref>Warner, Jennifer: ''[http://www.medicinenet.com/script/main/art.asp?articlekey=56520 Jury Still Out on Low-Carbohydrate Diets]'', MedicalNet.com, April 8, 2003</ref>
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. <ref>
[http://www.abc.net.au/news/newsitems/200409/s1192092.htm Study questions long-term Atkins effects - ABC News, 4 Sept 2004]</ref>
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.<ref>{{cite journal | author= Thomas L. Halton, Sc. D., Walter C. Willett, M.D., Dr. P.H., Simin Liu, M.D., Sc. D., JoAnn E. Manson, M.D., Dr. P.H., Christine M. Albert, M.D., M.P.H., Kathryn Rexrode, M.D., and Frank B. Hu, M.D., Ph. D. | title=Low-carbohydrate diet score and the risk of coronary heart disease in women | journal=New England Journal of Medicine | year=2006 | volume=355:1991-2002 | pmid = 17093250 }}</ref> Other studies have found possible benefits to individuals with diabetes,<ref>{{cite journal | pmid = 16318637 | doi = 10.1186/1743-7075-2-34 | last = Yancy | first = W.S. | coauthors = Foy M, Chalecki AM, Vernon MC, Westman EC. | year = 2005 | title = A low-carbohydrate, ketogenic diet to treat type 2 diabetes | journal = Nutrition & Metabolism | volume = 1 | pages = 34 | issue = 2 | url = http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1325029 }}</ref> cancer,<ref>{{cite journal | last = Bravi | first = F. | coauthors = Bosetti C, Scotti L, Talamini R, Montella M, Ramazzotti V, Negri E, Franceschi S, & La Vecchia C | journal = International Journal of Cancer | year = 2007 | volume = 120 | issue = 3 | pages = 681–5 | pmid = 17058282 | title = Food groups and renal cell carcinoma: A case-control study from Italy | doi = 10.1002/ijc.22225 }}</ref><ref>Sun Ha Jee, PhD, MHS; Heechoul Ohrr, MD, PhD; Jae Woong Sull, PhD, MHS; Ji Eun Yun, MPH; Min Ji, MPH; Jonathan M. Samet, MD, MS: Fasting Serum Glucose Level and Cancer Risk in Korean Men and Women, Journal of the American Medical Association, Vol. 293 No. 2, Jan. 12, 2005.</ref> and autism.<ref>{{cite journal | last = Evangeliou | first = A | coauthors = Vlachonikolis I, Mihailidou H, Spilioti M, Skarpalezou A, Makaronas N, Prokopiou A, Christodoulou P, Liapi-Adamidou G, Helidonis E, Sbyrakis S, Smeitink J. | title = Application of a ketogenic diet in children with autistic behavior: pilot study | journal = Journal of Child Neurology | year = 2003 | pmid = 12693778 | volume = 18 | issue = 2 | pages = 113–8 | doi = 10.1177/08830738030180020501}}</ref> 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.<ref>Freeman, John M.; Kossoff, Eric H.; Hartman, Adam L.: ''[http://pediatrics.aappublications.org/cgi/content/full/119/3/535 The Ketogenic Diet: One Decade Later]'', PEDIATRICS, Vol. 119 No. 3 March 2007, pp. 535-543</ref>
A study conducted in 1965 at the Oakland (California) Naval Hospital used a diet of 1000 [[calorie]]s 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 [[fasting|fasted]] completely. ([[#External sources|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.<ref>Schoeller, Dale: ''[http://www.medscape.com/viewarticle/493991_6 What's All the Excitement About Low-Carb?]'', [http://www.medscape.com Medscape] from WebMD, retrieved 19 Feb 2008</ref><ref>{{cite journal | author= Carol S Johnston, Sherrie L Tjonn, Pamela D Swan, Andrea White, Heather Hutchins and Barry Sears | title=Ketogenic low-carbohydrate diets have no metabolic advantage over nonketogenic low-carbohydrate diets | journal=American Journal of Clinical Nutrition | year=2006 | month=May | volume=83 | url=http://www.ajcn.org/cgi/content/abstract/83/5/1055 | pmid=16685046}}</ref><ref>{{cite journal | author=Linda Stern, MD; Nayyar Iqbal, MD; Prakash Seshadri, MD; Kathryn L. Chicano, CRNP; Denise A. Daily, RD; Joyce McGrory, CRNP; Monica Williams, BS; Edward J. Gracely, PhD; and Frederick F. Samaha, MD | title=The Effects of Low-Carbohydrate versus Conventional Weight Loss Diets in Severely Obese Adults: One-Year Follow-up of a Randomized Trial | journal=Annals of Internal Medicine | year=2004 | volume=140 | issue=10 | pages= 778–785 | url=http://www.annals.org/cgi/content/abstract/140/10/778?etoc | pmid=15148064}}</ref>
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. "<ref>[http://nutrition.stanford.edu/pdfs/AZ_press.pdf STANFORD DIET STUDY TIPS SCALE IN FAVOR OF ATKINS PLAN]'', Press Release, Standford University, 2007</ref><ref>Gardner CD, Kiazand A, Alhassan S, Kim S, Stafford RS, Balise RR, Kraemer HC, and King AC (2007), [http://jama.ama-assn.org/cgi/content/full/297/9/969 Comparison of the Atkins, Zone, Ornish, and LEARN Diets for Change in Weight and Related Risk Factors Among Overweight Premenopausal Women: The A TO Z Weight Loss Study: A Randomized Trial]. ''Journal of the American Medical Association'', Volume 297, Issue 9, Pages 969-977. PMID 17341711. Retrieved on [[September 13]], [[2007]].</ref>
A study at [[Duke University]] (2005) funded by an unrestricted grant from the Atkins Foundation, favored low-carbohydrate diets for both weight loss and health indicators.<ref>''[http://www.dukemednews.duke.edu/news/article.php?id=9412 Study Shows Low-Carb Diet Improves Cholesterol]'', Press Release, Duke University, 2005</ref>
==Criticism and controversies==
=== 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<ref name="The Protein Power Lifeplan">Eades, M. (1995) ''The Protein Power Lifeplan'', Warner Books. ISBN 0-446-67867-8</ref>). 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 ===
Some critics argue that low-carbohydrate diets can inherently cause weakness or fatigue<ref>Warning On Low Carb Diets[http://www.aphroditewomenshealth.com/news/20040209193533_health_news.shtml]</ref> giving rise to the occasional assumption 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 several days as the body adjusts) and indeed most highly recommend exercise as part of a healthy lifestyle.<ref name="The Protein Power Lifeplan">Eades, M. (1995) ''The Protein Power Lifeplan'', Warner Books. ISBN 0-446-67867-8</ref>
=== 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. Some critics have argued or implied that "carbohydrates contain [[vitamin]]s" and [[mineral]]s<ref>''[http://www.womenshealthchannel.com/nutrition-guide/carbohydrates.shtml Nutrition: Carbohydrates]'', Women's Health Channel, retrieved 13 March 2008</ref> but this suggestion is strictly false (by definition). While it is true that many foods that are rich in carbohydrates are also rich in vitamins and minerals, there are many low-carbohydrate foods that are similarly rich in vitamins and minerals.<ref>Cordain, Loren: ''[http://books.google.com/books?id=uloKAAAACAAJ&dq=the+paleo+diet The Paleo Diet]'', pages 106-107, Wiley, 2002, 272 pages, ISBN 0471413909</ref> Also, the important [[vitamin B12]] is only available in significant quantities from animal sources and not from vegetable sources.<ref>''[http://www.vegsoc.org/info/b12.html Vitamin B12]'', The Vegetarian Society, retrieved 13 March 2008</ref>
It should be noted that, contrary to the recommendations of most diet guides, some individuals may choose to avoid vegetables altogether in order to minimize carbohydrates. It is more likely that such a diet could be nutritionally deficient.
===Other controversies===
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]].
Some variants of low carbohydrate diets involve substantially lowered intake of [[dietary fiber]] which can result in [[constipation]] if not supplemented. For example, this has been a criticism of the [[Atkins Nutritional Approach#Induction|Induction stage]] of the [[Atkins Nutritional Approach|Atkins diet]] (note that today the Atkins diet is more clear about recommending a fiber supplement during Induction). Most advocates today argue that fiber is a "good" carbohydrate and in fact encourage a high-fiber diet.
It has been hypothesized that a diet related change in blood acidity can lead to bone loss through a process called [[ketoacidosis]], as mentioned earlier in this article. However ketoacidosis, which is often confused with ketosis, is an acute medical condition caused by extreme fasting or as a symptom of untreated diabetes, and is not likely to be induced by a proper low-carbohydrate diet.
One of the occasional side effects of a ketogenic diet is a noticeable smell of ketones in the urine, perspiration, and breath.<ref>Interview with Charles H. Perle, DMD - "Basically when you are on a low-carbohydrate diet, the key to success is breaking fat into ketones to create ketosis, and as ketones get into urine and saliva, it can cause horrible breath,"; WebMD feature; "Low-Carb Diets Can Cause Bad Breath"; http://www.medicinenet.com/script/main/art.asp?articlekey=52504</ref>
This is caused by the temporary metabolism of fatty-acid derived acetyl-coa into the ketone form, so that it may be released from the liver into the blood stream. The ketones are then re-assembled when they reach various body tissues to form acetyl-coa again, which is used as the precursor to energy.
==Books==
*''Good Calories, Bad Calories: Challenging the Conventional Wisdom on Diet, Weight Control, and Disease'', Gary Taubes, Knopf (2007), ISBN 978-1400040780
==See also==
*[[Diet (nutrition)|Diet]]
*[[Glycemic index]]
*[[Healthy diet]]
*[[Insulin resistance]]
*[[List of diets]]
*[[Medical research related to low-carbohydrate diets]]
*[[No-carbohydrate diet]]
==References==
{{reflist|2}}
==Sources==
* Eades, Michael R.; Eades, Mary Dan: ''Protein Power'', Bantam Books, 1999, ISBN 0553380788.
* Bowen, R.: ''[http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/pancreas/index.html The Endocrine Pancreas]'', Colorado State University: Hypertexts for Biomedical Sciences, 8 December 2002.
* ''[http://www.neuro.jhmi.edu/Epilepsy/keto.html The Ketogenic Diet]'', Johns Hopkins Epilepsy Center.
* Banting, William: ''[http://2020ok.com/books/25/letter-on-corpulence-addressed-to-the-public-19925.htm Letter On Corpulence]'', Addressed To The Public, 4th, London, England: Harrison, 1869.
* Bowden, Jonny: ''[http://books.google.com/books?id=U1Ju61Vgd8AC&pg=PA9&lpg=PA9&dq=history+%22low+carb%22&source=web&ots=fldtKP6aW6&sig=YpN6YVdZSJupCMZrEA-hkUAnwEU&hl=en#PPA6,M1 Living the Low Carb Life: From Atkins to the Zone]'', Sterling Publishing, February 2004, ISBN-13: 9781402713989, 352pp.
* Carr, Timothy P.: ''[http://books.google.com/books?id=z3Qp2z2ByV4C&pg=PA194&dq=glucagon+glycogen+ketone&sig=HWX132ylv-Es3A_LUPKWdxD-OHc#PPA72,M1 Discovering Nutrition]'', Blackwell Publishing, October 2002, ISBN: 9780632045648.
* Freeman, John M., Kossoff, Eric H., Freeman, Jennifer B.: ''[http://books.google.com/books?id=w8SLjhqr6VEC&printsec=frontcover&dq=the+ketogenic+diet&sig=1RyJPetoRSuLcPU-RWCyOPZMeL0#PPP1,M1 The Ketogenic Diet: A Treatment for Children and Others with Epilepsy]'', Fourth edition, Demos Medical Publishing, October 4, 2006, ISBN-13: 978-1932603187.
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