Low-carb diet

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“”Everything I am today, I owe to pasta.

—Sophia Loren

The low-carb diet (or 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. In a nutshell, it is reducing carbohydrates, especially those with high glycemic index (like sugars), eating proteins to maintain the need of amino acids, and eating fats to get the energy. 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.

Low-carb diets can improve short-term weight loss. Low carbohydrate diets with high amounts of animal fat and protein increase the risk of cancer, cardiovascular disease and all-cause mortality. The American Heart Association has scored low-carb diets poorly compared to their dietary guidelines which promote cardiometabolic health.

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? Generally, 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. However, although blood glucose is necessary, there is no "essential" carbohydrate, meaning that it is possible to live without ingesting a single gram. Glucose is created by the liver through a process known as gluconeogenesis. Most, but not all, of the proteins and fats that one's body needs can be synthesised by one's 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, and each one does a different thing in one's 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 20 g 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 (sucrose and high-fructose corn syrup are most common). 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. Unfortunately, the Western diet today contains all too much sugar and other processed high-glycemic index short-chain carbohydrates, which should be avoided anyway.

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. Instead of saturated fats, one should get one's lipid intake from unsaturated fats, such as olive, linseed or canola oil. Salad dressings made from these fats are a better idea for fat intake than eating butter straight from box.

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.

Ketogenic diet

Keto meal

The ketogenic diet (known as keto) is an established medical diet for treating children with epilepsy, under the supervision of a physician and dietician, and it requires vitamin and mineral supplementation for nutrients it does not supply (vitamin D, B vitamins, calcium, selenium, and others). However it is promoted by low-carb cranks as a cure for practically all diseases, including cancer. Side effects of the keto diet include acidosis, constipation, diarrhoea and dyslipidemia.

Like other fad diets, there is little evidence to suggest the ketogenic diet has beneficial long-term effects on weight maintenance.

A metabolic state promoted by low-carbers is ketosis, which is the basis of ketogenic diets, such as Atkins. Carbs initiate the secretion of insulin, which stores energy from bloodstream into fat tissue, whilst amino acids initiate the secretion of glucagon, which releases energy from fat tissue to bloodstream (gluconeogenesis). By avoiding carbohydrates, the dieter deliberately puts the body into ketosis (keeping insulin levels artificially low) and "cheats" the body into thinking it is starving. By eating fats, a third hormone, leptine, secretion is initiated: this hormone is the "containment" hormone that tells the appetite that no more food is needed. Once the body has used up the amino acids and lipids in bloodstream, it begins to convert the body fat into glucose and ketones. Essentially, the point is to trick your body into starving itself. Needless to say, this kind of body hacking is extremely dangerous if you do not know what you are doing.

Controlled ketogenic diet is used on the most serious cases of children's epilepsy. However, side effects have been reported. A 10-year study conducted on keto and epilepsy management in children discovered the following side effects: constipation (65%), high triglycerides (40%), high cholesterol (29%), diarrhea (19%), lethargy (17%), iron deficiency (15%), and vomiting (13%).

Long-term use of the ketogenic diet in children can increase the risk of stunted growth, bone fractures and kidney stones.

Low carb diets such as keto may cause ketoacidosis, a life threatening condition.

The British Dietetic Association (BDA) included the ketogenic diet in their list of "Top 5 worst celeb diets to avoid in 2018". According to the BDA:

A carefully dietitian-planned ketogenic diet can be a very effective treatment for people with epilepsy. For weight loss, there's no magic, the diet works like any other by cutting total calories and removing foods people tend to overeat. Initial side effects may include low energy levels, brain fog, increased hunger, sleep problems, nausea, digestive discomfort, bad breath and poor exercise performance. It can be an effective method of weight loss in the short term with careful planning but it is hard to sustain for many in the long term and most of the initial weight loss seen is often associated with water/fluid losses. It is never a good idea to ‘over-restrict’ any one food group (including carbohydrate), as this can mean it is more difficult to achieve a balanced diet overall with respect to vitamins, minerals and fibre in particular.

In the popular press, keto is associated with a variety of unpleasant side-effects, including keto flu, keto breath, keto diarrhea, and keto crotch (an unpleasant vaginal odor). As yet there aren't any scientific studies into the phenomena, but biochemistry indicates that the keto diet causes the body to increase its production of a variety of foul-smelling chemicals including acetoacetate, beta-hydroxybutyrate, and acetone (mmm, nail polish remover).

In 2021 the American Heart Association issued a scientific statement on dietary guidance to improve cardiovascular health which noted that "there is insufficient evidence to support any existing popular or fad diets such as the ketogenic diet and intermittent fasting to promote heart health".

A 2023 umbrella review of randomized clinical trials found that the ketogenic diet decreased seizure frequency and triglyceride levels but significantly increased low-density lipoprotein cholesterol (LDL-C).

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 kg of useless water which it dumps later, producing that famous initial quick weight loss.

Although a low-carbohydrate diet may cause quick weight loss, a Cochrane review from 2022 that examined longer periods of two years found no benefit for adhering to a low-carbohydrate diet in comparison to balanced diets.

Type 2 Diabetes

A 2018 consensus report on Type 2 Diabetes by the American Diabetes Association (ADA) and the European Association for the Study of Diabetes (EASD) found that a low-carbohydrate diet and the Mediterranean diet improved glycemic control, for patients with type 2 diabetes". A 2019 consensus report on nutrition therapy for adults with diabetes or prediabetes found that "Reducing overall carbohydrate intake for individuals with diabetes has demonstrated the most evidence for improving glycemia and may be applied in a variety of eating patterns that meet individual needs and preferences." and also conclude "These eating patterns are among the most studied eating patterns for type 2 diabetes."[87]

The American Diabetes Association's Standards of Medical Care in Diabetes—2019 include a variety of eating plans as acceptable for management of type 2 diabetes and prediabetes. Mediterranean diet, Dietary Approaches to Stop Hypertension (DASH) diet, plant based diets and, for most type 2 diabetics, low carbohydrate diets are included as Medical Nutrition Therapy options.

History

William Banting

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 19^th 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 (1930–2003), it has been around since the early 1970s and has been considered quackery by most of the medical community for most of its life. Medical experts have described the diet as pseudoscientific.

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 2003-2004. 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 caring about) portion size, or reminding adults to limit calories to a reasonable level for weight 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), while developing new zero-carbohydrate colas with less objectionable aftertaste than their older aspartame-laden diet colas.

In 2002, Gary Taubes wrote an article for the New York Times Magazine, "What if It's All Been a Big Fat Lie?" His article defended the Atkins diet and quoted medical authorities as supporting the diet. Upon investigation, Taubes had quoted the scientists out of context. None of them support the Atkins diet. Robert Atkins was clinically obese when he died in 2003 following a history of heart attack, congestive heart failure and hypertension.

Cardiologist William C. Roberts has noted that "Although dieters on the Atkins diet may lose weight, it's mainly water weight. They lose weight primarily because they have lost their appetites and decreased total caloric intake. Although telling people that pork rinds and sausage are good for them is a great way to sell books, it is irresponsible and dangerous. If a diet sounds too good to be true, it probably is. The Atkins diet produces bad breath, bad body odor, constipation, lethargy, and occasionally lightheadedness."

The reality of low carb, higher protein diets

There is a two-fold reality to truly low carb diets: 1) They work in the short term 2) They are dangerous.

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.

Granted, low-carb diets can be astonishingly effective. But given their side effects, they can be suggested only when the overweight itself presents graver dangers to the health of the patient than the risks of the diet. Morbidly obese patients (weight index ~38+) may benefit from low carbohydrate diets in order to normalize their body weight. Such diet should always be considered only as the means, not the end.

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. 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.

If you attempt low carbohydrate diet, you should never cut vegetable and legume intake, but rather that of the processed carbohydrates, such as sugar, bread, pasta, potato chips and cereals. Berries and nuts are healthier than fruits, which in turn are healthier than processed flour products. (The official Atkins plan, in particular, specifically states that most — as in, 75% and up — of your total net carb intake should be from vegetables.) Instead of meat you should favour fish, crustaceans, mollusks, avians and tofu as the protein sources, and instead of saturated fats the vegetable fats, such as olive and canola oil.

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.

A 2018, prospective cohort study and meta-analysis found that low-carbohydrate diets rich in animal fat and protein are associated with increased mortality. This association has been confirmed in other recent reviews.

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.

Modern LCHF movement

In recent years the Low-Carb High-Fat diet (LCHF) has been promoted in popular books and on social media platforms. A common theme amongst LCHF proponents is the use of anecdotal evidence and promotion of Big Pharma conspiracy theories. Because of its dogma and fundamentalist tactics, critics have referred to LCHF as a cult and form of "religious zealotry". LCHF advocates are associated with cholesterol denialism.

Because of their high cholesterol and fat content LCHF diets increase the risk of cardiovascular disease. Diets high in saturated fat also increase the risk of Alzheimer's disease and dementia. A low-carb diet also increases the risk of atrial fibrillation (AFib), the most common heart rhythm disorder.

Modern promoters

Low-Carb High-Fat promoters include:

• Shawn Baker
• Eric Berg
• Jason Fung
• Zoë Harcombe
• Anatoly Karlin
• Malcolm Kendrick
• Aseem Malhotra
• Max Lugavere
• Tom Naughton
• Tim Noakes
• Uffe Ravnskov
• Marika Sboros
• Gary Taubes
• David Unwin

See also

• Carnivore diet
• Statin denialism

External links

• AtkinsExposed.org
• Feeling euphoric on a low-carb diet? The effect on your brain is similar to an illicit drug
• Low-Carbohydrate Diets - Quackwatch