Atkins diet

Atkins diet, officially called the Atkins Nutritional Approach, is a low-carbohydrate diet created by Robert Atkins from a research paper he read in the Journal of the American Medical Association published by Gordon Azar and Walter Lyons Bloom. Atkins stated that he used the study to resolve his own overweight condition. He later popularized the method in a series of books, starting with Dr. Atkins' Diet Revolution in 1972. In his second book, Dr. Atkins' New Diet Revolution, he modified parts of the diet but did not alter the original concepts.

Ketogenic diet

The induction phase of the Atkins diet is a ketogenic diet. In ketogenic diets there is production of ketones that contribute to the energy production in the Krebs cycle. Ketogenic diets rely on the insulin response to blood glucose. Because ketogenic dieters eat few carbohydrates, there is no glucose that can trigger the insulin response. When there is no glucose-insulin response there are some hormonal changes that cause the stored fat to be used for energy. Blood glucose levels have to decrease to less than 3.58 mmol/L for growth hormone, epinephrine, and glucagon to be released to maintain energy metabolism. In the adipose cells, growth hormone and epinephrine initiate the triacylglycerol to be broken down to fatty acids. These fatty acids go to the liver and muscle where they should be oxidized and give acetyl-CoA that enters the Krebs cycle directly. However, the excess acetyl-CoA in the liver is converted to ketones (ketone bodies), that are transported to other tissues. In these tissues they are converted back into acetyl-CoA in order to enter the Krebs cycle. Glucagon is produced when blood glucose is too low, and it causes the liver to start breaking glycogen into glucose. Since the dieter does not eat any more carbohydrates, there is no glycogen in the liver to be broken down, so the liver converts fats into free fatty acids and ketone bodies, and this process is called ketosis. Because of this, the body is forced to use fats as a primary fuel source.

Main effects

The effects of the Atkins diet remain a subject of much debate. Some studies conclude that the Atkins diet helps prevent cardiovascular disease, lowers the low density lipoprotein (LDL) cholesterol, and increases the amount of HDL, or so-called "good" cholesterol. Some studies suggest that the diet could contribute to osteoporosis and kidney stones. A University of Maryland study, in which test subjects were given calorie increases whenever their weight started to drop, showed higher LDL cholesterol and markers for inflammation.

Cholesterol

According to Harper (2004) in a year-long study, the concentration of HDL cholesterol increased, and insulin resistance improved much more in dieters following the Atkins diet than in those following a low-fat, calorie restricted diet. Harper also mentions that there had not been enough prior research to allow him to confidently say that Atkins is safe to be recommended to patients.

Barnett TD, Barnard NDB, Radak TLR (2009). "Development of symptomatic cardiovascular disease after self-reported adherence to the Atkins diet". Journal of the American Dietetic Association 109.

Methylglyoxal

A 2005 study by Beisswenger and colleagues compared levels of the glycotoxin methylglyoxal (MG) before and after starting the Atkins diet. MG is associated with blood vessel and tissue damage, and is higher in people with poorly controlled diabetes. The study found that MG levels doubled shortly after the diet was started, noting that the MG rise was related to the presence of ketosis. A rise in acetol and acetone was found, indicating that MG was produced by oxidation. MG also arose as a by-product of triglyceride breakdown and from lipoxidation (ketosis related to fat intake).

Whether or not increased methylglyoxal is harmful to human beings has been questioned by the Indian Association for the Cultivation of Science, who in a 2008 critical overview of various studies (including Beisswenger's study) state, "The authors present a brief critical overview of studies indicating both toxic and beneficial effects of methylglyoxal and suggest that the beneficial effects of methylglyoxal outweigh its toxic effects." While not drawing any definite conclusions, the Indian Association for the Cultivation of Science recommends further study especially in the area of using methylglyoxal to cure or treat cancer.

The four phases

There are four phases of the Atkins diet: induction, ongoing weight loss, pre-maintenance and lifetime maintenance.

Induction

Induction is the most restrictive phase of the Atkins Nutritional Approach. Two weeks are recommended for this phase. It is intended to cause the body to quickly enter a state of ketosis. Carbohydrate intake is limited to no more than 20 net grams per day (grams of carbohydrates minus grams of fiber, sugar alcohols, or glycerin), 12 to 15 net grams of which must come in the form of salad greens and other fruits and vegetables such as broccoli, spinach, pumpkin, cauliflower, turnips, tomatoes, and asparagus, to name a few of the 54 allowed by Atkins (but not legumes, since they are too starchy for the induction phase). The allowed foods include a liberal amount of all meats, poultry, fish, shellfish, fowl, and eggs; up to 4 ounces (113 g) of soft or semi-soft cheese such as cheddar cheese; most salad vegetables; other low carbohydrate vegetables; and butter, olive oil and vegetable oils. Drinking eight glasses of water per day is a requirement during this phase. Alcoholic beverages are not allowed during this phase. Caffeine is allowed in moderation so long as it does not cause cravings or low blood sugar. If a caffeine addiction is evident, it is best to not allow it until later phases of the diet. A daily multivitamin with minerals, except iron, is also recommended. A normal amount of food, on Induction, is around 20 grams of sugar (or net carb), at least 100 grams of fat.

The Induction phase is usually when many see the most significant weight loss — reports of losses of 5 to 10 pounds per week are not uncommon when Induction is combined with daily exercise. Many Atkins followers make use of Ketostix, small chemically reactive strips used by diabetics. These let the dieter monitor when they enter the ketosis, or fat burning, phase, but are not always accurate for non-diabetic users. Other indicators of ketosis include a metallic taste in the mouth, or a sweet smell on breath (the smell of Ketones).

Ongoing weight loss

The Ongoing Weight Loss (OWL) phase of Atkins consists of an increase in carbohydrate intake, but remaining at levels where weight loss occurs. The target daily carbohydrate intake increases each week by 5 net grams per day. A goal in OWL is to find the "Critical Carbohydrate Level for Losing" and to learn in a controlled manner how food groups in increasing glycemic levels and foods within that group affect your craving control. The OWL phase lasts until weight is within 10 pounds (4.5 kg) of the target weight.

During the first week, one should add more of the induction acceptable vegetables to one's daily products. For example, 6-8 stalks of asparagus, salad, one cup of cauliflower or one half of avocado. The next week, one should follow the carbohydrate ladder that Dr Atkins created for this phase and add fresh dairy. The ladder has 9 rungs and should be added in order given. One can skip a rung if one does not intend to include that food group in one's permanent way of eating, such as the alcohol rung.

The rungs are as follows:

Induction of acceptable vegetables in larger quantities

Fresh cheese

Nuts and seeds

Berries

Alcohol

Legumes

Other fruits

Starchy vegetables

Whole grains

Pre-maintenance

Daily net carbohydrates intake is increased again this time by 10 grams each week from the latter groupings, and the key goal in this phase is to find the "Critical Carbohydrate Level for Maintenance", this is the maximum number of carbohydrates you can eat each day without gaining weight. This may well be above the level of carbohydrates inducing ketosis on a testing stick. As a result, it is not necessary to maintain a positive ketosis test long term.

Lifetime maintenance

This phase is intended to carry on the habits acquired in the previous phases, and avoid the common end-of-diet mindset that can return people to their previous habits and previous weight. Whole, unprocessed food choices are emphasized, with the option to drop back to an earlier phase if you begin to gain weight.

Popularity

The Atkins Nutritional Approach gained widespread popularity in 2003 and 2004. At the height of its popularity one in eleven North American adults was on the diet. This large following was blamed for large declines in the sales of carbohydrate-heavy foods like pasta and rice: sales were down 8.2 and 4.6 percent, respectively, in 2003. The diet's success was even blamed for a decline in Krispy Kreme sales. Trying to capitalize on the "low-carb craze," many companies released special product lines that were low in carbohydrates. Coca-Cola released C2 and Pepsi-Cola created Pepsi Edge, which was scheduled to be discontinued later in 2005. Unlike the sugar-free soft drinks Diet Coke and Diet Pepsi, which had been available for decades, these new drinks used a blend of sugar and artificial sweeteners to offset the flavor of artificial sweetener. These "half-and-half" drinks declined in popularity as soft drink makers learned to use newer sweeteners to mask the flavour of aspartame (or completely replace it) in reformulated diet drinks such as Coca-Cola Zero and Pepsi ONE.

Low-carbohydrate diets and the societal changes they have caused have been a subject of interest in the news and popular media. For example, on 25 April 2004, Canada's Food Network aired a one-hour television documentary entitled The Low Carb Revolution.

Nature of the diet

The Atkins diet involves limited consumption carbohydrates to switch the body's metabolism from metabolizing glucose as energy over to converting stored body fat to energy. This process, called ketosis, begins when insulin levels are low; in normal humans, insulin is lowest when blood glucose levels are low (mostly before eating). Ketosis lipolysis occurs when some of the lipid stored in fat cells are transferred to the blood and are thereby used for energy. On the other hand, caloric carbohydrates (for example, glucose or starch, the latter made of chains of glucose) impact the body by increasing blood sugar after consumption. (In the treatment of diabetes, blood sugar levels are used to determine a patient's daily insulin requirements.) Lastly, because of fiber's low digestibility, it provides little or no food energy and does not significantly impact glucose and insulin levels.

In his book Dr Atkins' New Diet Revolution, Atkins made the controversial argument that the low-carbohydrate diet produces a metabolic advantage because "burning fat takes more calories so you expend more calories. He cited one study where he estimated this advantage to be 950 calories (4.0 MJ) per day. A review study published in the Lancet concluded that there was no such metabolic advantage and dieters were simply eating fewer calories because of boredom. Professor Astrup stated, "The monotony and simplicity of the diet could inhibit appetite and food intake".

The Atkins Diet restricts "net carbs" (digestible carbohydrates that impact blood sugar). One effect is a tendency to decrease the onset of hunger, perhaps because of longer duration of digestion (fats and proteins take longer to digest than carbohydrates). Atkins states in his 2002 book New Diet Revolution that hunger is the number one reason why low-fat diets fail and that the Atkins diet is easier because you are allowed to eat as much as you want.

Net carbohydrates can be calculated from a food source by subtracting fiber and sugar alcohols (which are shown to have a smaller effect on blood sugar levels) from total carbohydrates. Sugar alcohols contain about two calories per gram, and the American Diabetes Association recommends that diabetics count each gram as half a gram of carbohydrate. Fructose (for example, as found in many industrial sweeteners) has four calories per gram but has a very low glycemic index and does not cause insulin production, probably because ß cells have low levels of GLUT5.