“”Everything I am today, I owe to pasta.
The low-carb diet (also, Low-Carb High Fat (LCHF)) has been popularized in recent years through many fad diets such as Atkins, SugarBusters!, The Zone, South Beach Diet, Protein Power, the paleo diet, Tim Ferriss' slow-carb diet and several others. The variety of low carb diets, and the revisions of existing low/lower carb diets has produced a range of low and lower carb diets that are healthy ways to lose weight. However, there are still a host of woo-related low carb and no-carb fad diets out there.
 Carb, protein, fat?
Before any explanation of this can begin, it is important to understand what carbohydrates, protein, and fat are. Everything you consume, at a nutritional level, is water, a mineral, a micronutrient, or a macronutrient. Minerals are non-organic substances that your body needs to survive, like calcium and iron. How do we know, or rather define, them as organic or inorganic? Basically, if it has carbon in it, it is organic. Simple as that. Micronutrients are generally vitamins.
Carbohydrates, protein, and fat are macronutrients and they give your body calories. Each one has their own properties based on the composition of their elements (each having a unique mixture and structure of carbon, hydrogen, and oxygen), and other chemicals that make up the specific molecules. Each one plays a different role in your body and gives a different amount of calories per gram (4 per gram of protein or carbohydrate, and 9 per gram of fat). There's a huge and technical listing of things that each one does and how they function, and their relation to each other and every other element of your nutrition, especially when you start talking about the different kinds of carbohydrates, protein, and fat. The short version is that fat is used by your body to maintain things like your skin, hair, fingernails and teeth, protein is used to build and maintain muscles, some internal organs, and the like. Normally, carbohydrates are used to fuel everything else, especially your nervous system and your brain. Most, but not all, of the proteins and fats your body needs can be synthesized by your body from other available macronutrients; the few that can't be are called essential amino acids and essential fatty acids, respectively.
Remember: There are actually different kinds of each of these, each one does a different thing in your body.
 The basic low-carb theory
The low-carb theory of diet is based on the relationship between blood glucose levels and the hormone insulin, and insulin's role in regulating fat storage in the human body. When one eats a meal high in carbohydrate content, blood sugar rises. In response the pancreas produces insulin. Insulin not only helps cells metabolize glucose but it also regulates the storage of fat in cells, particularly fat tissue. When insulin levels are high, fat storage is high. When insulin levels are low, stored fat is released and little new fat storage occurs. When there is no insulin (Type 1 Diabetes) there is no fat storage.
Low-carb diets reduce dietary carbohydrates dramatically, which reduces blood sugar levels and eliminates blood sugar spikes and the resulting blood sugar/insulin swings. Typically carbs are reduced to below ten percent of total caloric intake. The Atkins diet induction phase, for example, reduces carb intake to less than 20g per day, most coming from complex carbs. Most low-carb diets also moderate intake of protein and increase dietary fat, and are often referred to as Low-Carbohydrate, High-Fat (LCHF) diets.
This theory is partially accurate. The issue is that there are different kinds of carbohydrates, loosely broken into simple and complex. Simple carbohydrates are sugars, like, well, sugar. Complex carbohydrates include starch and "fiber." While you can get starch from white flour and white rice, you can only get fiber from eating "whole grains", like wheat bread, brown rice, and rye bread, for example. You can also get fiber from eating certain fruits and vegetables. The difference is really only how complex the molecular chain is, which impacts how difficult it is for your body to break up, and then use. During digestion, simple carbohydrates can be absorbed into your blood stream very quickly with little or no modification. Starches take longer to break down, and so enter the blood stream more slowly when eaten. Fiber is difficult for your body to break down at all, and most of it goes right through you and out the other end undigested. The low-carb theory above is accurate, but only with simple sugars..
Once blood glucose levels have remained consistently low for a period of time (typically two to three days) the body adapts and the liver begins to produce ketones from free fatty acids. Ketones can be metabolized by many cells in the body including those cells that cannot directly metabolize fat. Once the body's production of ketones reaches a certain level the body is in nutritional ketosis. When the body is in nutritional ketosis fat becomes the primary energy source, and the body metabolizes stored fat and dietary fat.
Several of the popular low-carb diets (specifically Atkins) are high in saturated fats and excessive in protein intake, leading to increased risk of several diseases from kidney stones to heart disease. Critics note that the same weight loss could be achieved through other diets which do not involve such an unhealthy intake of saturated fats.
Low-carb diets became popular after sensational stories of rapid weight loss, but the real reason for the weight loss is low-carb diets are so restrictive that most people who try to follow them wind up drastically reducing their caloric intake, especially that consisting of sugary foods. (That, and the fact that losing weight on the first week or two of any new diet is pretty easy, because you're just shedding water weight and the body's starvation response hasn't kicked in yet.) Proponents claim the diets make the subject want to eat less in total, and there is some evidence for this.
 Does it work?
Basically, no. Your body needs carbohydrates to survive, just as any nutrient in food, and the idea behind it really doesn't make a whole lot of sense if you look at it in terms of our evolutionary history. Early humans (in the Paleolithic period) were generally agreed to be long distance runners, who would chase animals till they died of exhaustion, or became paralyzed by heat stroke and could not run or fight when caught up with by their hunters. Humans are one of the few species that are able to run for long distances at close to max speed, and we used this to chase prey animals 15-20 miles until we could just club them to death. This is, first of all, not a method of hunting that lends itself to a high protein diet. And as any long distance runner or cyclist will tell you, you need carbs a lot more than you need protein when you're doing a long run.
Furthermore, getting the majority of your calories from protein and fat puts you at a much higher risk for disease. Looking at available research will tell you that you aren't getting sick from eating bananas or potatoes but from eating high protein, fatty foods; e.g. that McDonalds double cheeseburger. Human physiology is quite comparable to that of our wild primate cousins. With this in mind, looking at what chimps, for example, are eating and what we are eating, there appears a strong discord. While chimps get almost all of their calories from fruits and leaves (carbs) we tend to eat only half of our calories from carbs. This is already significantly lower and likely telling of what might be wrong. To limit carbs even further doesn't make sense.
 Why does it seem to work?
Low-carb diets do not actually work, and are, in fact, kind of dangerous. But, they are still very popular because they seem to work. Why is this? Well, weight loss all comes down to calorie counting. Basically, one pound of body fat is about 3,500 calories. If you want to lose that weight, you need to burn 3,500 calories more than you get. A safe amount of weight loss is 1-2 pounds a week, so if you use 500 calories a day more than you consume, you will lose one pound by the end of the week. Some people like to claim that calorie accounting does not work, but, a lot of doctors seem to disagree, thinking either that low carb is not a good idea or that calorie cutting is. So, low carb diets seem to work because you eat fewer calories. Simple as that (but misguided). When you cut carbs, you cut breads and grains (and in extreme cases, fruits and vegetables), which may seem to be a quick way to dodge fast-burning calories. Likewise, the foods that are high in fat and protein tend to be very filling because fat and protein digest slowly in the stomach.
So, basically, low carb diets seem to work because they make you do what you should be doing anyway.
 Initial quick weight loss
Our body has some reserves of carbohydrates in form of glycogen, which is mostly contained in liver and muscles. The average human has about 200 g of glycogen (which can be drained by about as little as 1.5 hours of continuous exercise). Our body usually tries to maintain glycogen supply, because it's critical for high-intensity physical work, and if no carbs are available, the body will convert amino acids into carbs. But when there is not enough protein, the glycogen reserve eventually will be drained. Unlike fat, glycogen holds a lot of water with it, about ten times its own weight. After the reserve of glycogen is drained by low-carb (but not balanced!) diet, the body has about 2 kgs of useless water which it dumps later, producing that famous initial quick weight loss.
In 1797 John Rollo reported on the results of treating two diabetic Army officers with a low-carbohydrate diet and medications. A very low-carbohydrate, ketogenic diet was the standard treatment for diabetes throughout the 19th century.
In 1863 William Banting, a formerly 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 1888, James Salisbury introduced the Salisbury steak as part of his high-meat diet, which limited vegetables, fruit, starches, and fats to one-third of the diet.
In 1967, 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 United States. Other low-carbohydrate diets in the 1960s included the Air Force Diet and the Drinking Man’s Diet. Austrian physician Wolfgang Lutz published his book Leben Ohne Brot (Life Without Bread) in 1967. However, it was not well-known in the English-speaking world.
In 1972, Robert Atkins published Dr. Atkins Diet Revolution which advocated a low-carbohydrate diet he had successfully used in treating patients in the 1960s (having developed the diet from a 1963 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 Atkins had done little real research into his theories and based them mostly on his clinical work. Later that decade, Walter Voegtlin and Herman Tarnower published books advocating the paleolithic diet and Scarsdale diet, respectively, each meeting with moderate success.
 The Atkins Diet
The Atkins Diet is the best known low-carb diet. Started by Robert Atkins, it has been around since the early 1970s and has been considered quackery by most of the medical community for most of its life. After years as a fringe fad diet, for some reason it took off in popularity from about 1998-2004 and spawned a low-carb diet craze that peaked in 2003-04. In general, the dieter is advised to restrict carbs, pushing the body into ketosis. Ketosis is the state of the body burning fats (free fatty acids and ketone bodies), rather than carbohydrates for its primary source of energy. The body, and specifically the brain, cannot function properly on ketone energy alone. In theory one eats as much as one wants, until one is no longer hungry. Protein and fat, the two major components of the diet, do take longer to digest, so it is true one stays satisfied, longer. However, the diet (especially those who follow the diet casually) does not do a good job in teaching (or even care about) portion size, or reminding adults to limit calories to a reasonable level for loss or maintenance.
The Atkins diet has been criticized for its high fat content, especially saturated fats, its low fiber content and that it doesn't limit intake at all. The updated "Atkins diet," from Atkins Nutritionals, a company that was once owned by now-deceased Atkins, but since invested in by Parthenon Capital and Goldman Sachs, then bankrupted, then purchased by North Castle Partners, then sold to Roark Capital Group (i.e. totally unrelated to the original Atkins diet), provides for a higher intake of vegetables than the original, which may provide sufficient fiber.
Several imitators, most notably South Beach and The Zone, remain popular; others like SugarBusters! (a brief craze in 2001) came and went during this time. The inevitable special product lines of low-carb foods proved to be a boon for bargain shoppers when they were marked down to clearance prices once the fad was over. Ironically, the special product lines branded with the South Beach Diet and The Zone brands are laden with - guess what - sugar (although the Atkins and SugarBusters! product lines, to their credit, were not.) So much for "low carb" - sugar is sugar. Both Coca-Cola and Pepsi even got in on the fad with special "half the carbs" mixes (both now discontinued), which were still nonetheless full of high fructose corn syrup (which is sugar). Why they didn't just push their diet drinks, which have zero carbohydrate, no one knows.
 The reality of low carb, higher protein diets
The reality with any "Very high protein"(VHP) or "Very low carbohydrate"(VLC) is that they are helpful for short periods of time, but pushing the body into ketosis for extended periods, or asking the body to process high levels of protein leads to a variety of mild to major conditions, including: increased risk of heart disease; kidney dysfunction, liver dysfunction, bone density loss, arthritis, water retention, kidney stones and bad breath (ketoacidosis causes a fruity smell on the breath due to increased acetone in the body) and body odor. So while it does work, it is something best done under the guidance of a physician or dietician (not a nutritionist) and only for short periods of time.
The other problem with high protein diets is that according to several studies, the weight is more quickly regained than with dieters who followed a moderate reduction in calories over a longer time, presumably due to the fact that the weight was lost under the body's "duress", and not simply because more calories were spent than eaten.
 Lower carbs + meat = higher mortality
On 7 September 2010, two cohort studies on L-C diets were published together in the Annals of Internal Medicine (Harvard). The participating subjects were 85,168 women (aged 34 to 59 years at baseline) and 44,548 men (aged 40 to 75 years at baseline) without heart disease, cancer, or diabetes. The women were tracked from 1980 to 2006; the men from 1986 to 2006. The results: Animal-based L-C diets were associated with higher all-cause mortality, while vegetable-based L-C diets were associated with reduced all-cause mortality in general, and cardiovascular mortality in particular. This is an important distinction because ol' Doc Atkins claimed that eating a lot of meat was good for your heart. It should be noted that the fats consumed in an animal-based diet tend to contain a higher percentage of saturated fats than the fats in a vegetable-based diet, which would go a long way toward explaining the differences in cardiovascular mortality risk between such diets.
Incidentally, Dr. Atkins died of a slip-and-fall accident in 2003. At six feet and 258 pounds, he would have been described as obese by the CDC, and his death certificate is listed as such. However, his wife has contended that he only weighed 195 pounds (which is listed on medical records at the time he was admitted to the hospital) and the 60+ pounds of weight gain was attributed to bloating during a 9-day coma. There would be an irony in his weight, were it not under dispute.
 Saner alternative
More "moderate" low-carb diets can be very useful. Sometimes, but not always, obesity can worsen due to excess carbohydrates from unhealthy sources like white bread and pasta, desserts, and soda. By eliminating or drastically reducing these things from one's diet, one is essentially cutting carbs, and people have lost 30+ lbs. by doing this alone. Other carbs like whole wheat, fruits, and veggies are very much essential, however, and probably shouldn't get the axe. If you eat too few carbs, you can enter ketosis, which is a state where the body burns fat in place of carbs for energy. This should not be confused with ketoacidosis, which is an uncontrolled form of ketosis that is primarily associated with Type 1 Diabetes. 
 "Good" or "bad" carbs?
Ultimately, all carbohydrates — other than dietary fiber, which is not digested — enter the blood stream as monosaccharide sugars:
- Starches get broken down into maltose and maltotriose by amylase in the saliva, which in turn are broken down into glucose by maltase in the gut.
- Sucrose (table sugar) is broken down into fructose and glucose by sucrase in the gut.
- Lactose (milk sugar) is broken down into galactose and glucose by lactase in the gut, unless you're lactose intolerant in which case it isn't broken down or absorbed at all.
- Fructose and glucose (e.g. honey or high fructose corn syrup) are already monosaccharides, and don't need to be broken down.
In fibrous carbohydrate sources, such as whole grains or fruits, most of the carbohydrate is still in the form of starches or sugars; only a small percentage is dietary fiber. A typical apple, for example, contains 13 grams of sugar and 3 grams of fiber, while a cup of whole grain wheat flour contains 72 grams of starch and 15 grams of fiber. Even a serving of pure oat bran contains 18 grams of starch and only 6 grams of fiber.
A crucial difference between different kinds of carbohydrates is how rapidly they're broken down and absorbed into the blood stream, and how "sharp" a spike in blood sugar one experiences after eating them. The glycemic index is one (popular) attempt to quantify this. The glycemic index of a particular foodstuff is calculated by making test subjects eat an amount of the foodstuff that contains 50 grams of total carbohydrate; the subjects' blood glucose is then measured at regular intervals over the next two hours, and the glycemic index is derived from the size of the response curve. Unfortunately, the glycemic index isn't scaled for a reasonable portion size; measuring the G.I. of carrots, for example, requires the test subject to eat a pound and a half of carrots. A more sane quantity, called the glycemic load, is scaled for portion size, but glycemic load data are much more difficult to come by than glycemic index data.
- ↑ There are exceptions to this. Alcohol, non-vitamin anti-oxidants, and fiber are common examples. So is caffeine. Some are important, like fiber, some are not.
- ↑ Caloric content of fat, protein, carbohydrates and alcohol
- ↑ Even though it isn't a macronutrient, alcohol also gives calories, specifically 7 per gram of alcohol
- ↑ The Fighters Body, Loren W. Christensen and Wim Demeere
- ↑ An explanation of how this works on a chemical level that is both indepth and non-technical can be found []
- ↑ http://www.hsph.harvard.edu/nutritionsource/carbohydrates/carbohydrates-and-blood-sugar/
- ↑ Anne L. Stock, John Yudkin. "Nutrient Intake of Subjects on Low Carbohydrate Diet Used in Treatment of Obesity." Am J Clin Nutr July 1970 vol. 23 no. 7 948-952.
- ↑ Livestrong recommends 50-55% of Calories come from carbohydrates
- ↑ | like here
- ↑ To prove my point, here is a large list of articles that think so:
- Astrup, Arne; Larsen, Thomas Meinert; Harper, Angela (2004). "Atkins and other low-carbohydrate diets: Hoax or an effective tool for weight loss?". The Lancet 364
- Kappagoda, C.Tissa; Hyson, Dianne A.; Amsterdam, Ezra A. (2004). "Low-carbohydrate–high-protein diets". Journal of the American College of Cardiology 43
- High-Protein Diets, American Heart Association, 18 July 2008.
- Starchy foods, Food Standards Agency, retrieved 2 August 2008. It states
- Cutting out starchy foods, or any food group, can be bad for your health because you could be missing out on a range of nutrients. Low-carbohydrate diets tend to be high in fat, and eating a diet that is high in fat (especially saturated fat from foods such as meat, cheese, butter and cakes) could increase your chances of developing coronary heart disease.
- So, rather than avoiding starchy foods, it's better to try and base your meals on them, so they make up about a third of your diet.
- ↑ Weigle, DS; Breen, PA; Matthys, CC; Callahan, HS; Meeuws, KE; Burden, VR; Purnell, JQ (2005). "A high-protein diet induces sustained reductions in appetite, ad libitum caloric intake, and body weight despite compensatory changes in diurnal plasma leptin and ghrelin concentrations". The American journal of clinical nutrition 82
- ↑ Morgan, William (1877). Diabetes mellitus: its history, chemistry, anatomy, pathology, physiology, and treatment. http://books.google.com/books?id=1CIDAAAAQAAJ.
- ↑ Einhorn, Max (1905). Lectures on dietetics. http://books.google.com/books?id=utZqUyKmffIC.
- ↑ William Banting (1869). Letter On Corpulence, Addressed to the Public (4th ed.). London, England: Harrison. http://2020ok.com/books/25/letter-on-corpulence-addressed-to-the-public-19925.htm. Retrieved 2008-01-02.
- ↑ Barry Groves (2002). "William Banting Father of the Low-Carbohydrate Diet". The Weston A. Price Foundation. http://www.westonaprice.org/knowyourfats/banting.html.
- ↑ 1967: the Stillman diet – History Of Diets, Part 12 – protein diet Men's Fitness. June 2003
- ↑ Air Force Diet. Toronto, Canada, Air Force Diet Publishers, 1960.
- ↑ Gardner Jameson and Elliot Williams (1964) The Drinking Man’s Diet. San Francisco: Cameron. (2004) Revised Ed. ISBN 978-0-918684-65-3. See also Alan Farnham (2004) “The Drinking Man’s Diet”, Forbes.com.
- ↑ Lutz, Wolfgang; Allan, C.B. Life Without Bread. McGraw-Hill; 2000. ISBN 978-0-658-00170-3. English language, 1st Ed.
- ↑ The History of the Atkins Diet‚ A Revolutionary Lifestyle
- ↑ A critique of low-carbohydrate ketogenic weight reduction regimens. A review of Dr. Atkins' diet revolution., Journal of the American Medical Association, 1973
- ↑ Voegtlin, Walter L. (1975). The stone age diet: Based on in-depth studies of human ecology and the diet of man. Vantage Press. ISBN 0-533-01314-3.
- ↑ http://www.atkins.com/New-Book/Why-a-new-Atkins-book.aspx
- ↑ Parthenon, Goldman take control of Atkins - The Dealmakers - MarketWatch. http://www.marketwatch.com/story/parthenon-goldman-take-control-of-atkins
- ↑ The reconditioning of Atkins Nutritional http://finance.fortune.cnn.com/2010/12/10/the-reconditioning-of-atkins-nutritionals/
- ↑ "It now takes a healthier approach to eating than it previously did. It encourages eating more high-fiber vegetables, accommodates vegetarian and vegan needs, and addresses health problems that may arise when initially starting a low-carb diet"|http://www.mayoclinic.com/health/atkins-diet/MY00648
- ↑ Effects of a LC diet vs. MC diet in obese men
- ↑ http://www.ncbi.nlm.nih.gov/pubmed/15007396 pub med: long term benefits and risks
- ↑ Johns Hopkins, The Dangers of High-Protein, Low-Carbohydrate Diets for People With Diabetes
- ↑ Diets are classified in medical literature as VHP, HP, MP (moderate) and LP
- ↑ Here too, VHC (Very High Carbohydrate), HC, MC, LC (Low Carb), VLC.
- ↑ http://women.webmd.com/guide/high-protein-low-carbohydrate-diets
- ↑ Fung, Teresa T., et al. Abstract of "Low-Carbohydrate Diets and All-Cause and Cause-Specific Mortality: Two Cohort Studies", Annals of Internal Medicine, 153.5 (2010): 289-98.
- ↑ Ornish, Dean. "Atkin's Diet Increases All-Cause Mortality", Huffington Post, 7 September 2010.
- ↑ Even Snopes isn't sure yet
- ↑ http://en.wikipedia.org/wiki/Ketosis
- ↑ This gives the bacteria living in your colon an opportunity to feast on lactose, which they ferment into methane.