Dieting is the practice of eating food in a regulated and supervised fashion to decrease, maintain, or increase body weight. In other words, it is conscious control or restriction of the diet. A restricted diet is often used by those who are overweight or obese, sometimes in combination with physical exercise, to reduce body weight. Some people follow a diet to gain weight (usually in the form of muscle). Diets can also be used to maintain a stable body weight and improve health. In particular, diets can be designed to prevent or treat diabetes.
Diets to promote weight loss can be categorized as: low-fat, low-carbohydrate, low-calorie, very low calorie and more recently flexible dieting. A meta-analysis of six randomized controlled trials found no difference between low-calorie, low-carbohydrate, and low-fat diets, with a 2–4 kilogram weight loss over 12–18 months in all studies. At two years, all calorie-reduced diet types cause equal weight loss irrespective of the macronutrients emphasized. In general, the most effective diet is any which reduces calorie consumption.
A study published in American Psychologist found that short-term dieting involving “severe restriction of calorie intake” does not lead to “sustained improvements in weight and health for the majority of individuals”. Other studies have found that the average individual maintains some weight loss after dieting. Weight loss by dieting, while of benefit to those classified as unhealthy, may slightly increase the mortality rate for individuals who are otherwise healthy.
The first popular diet was “Banting”, named after William Banting. In his 1863 pamphlet, Letter on Corpulence, Addressed to the Public, he outlined the details of a particular low-carbohydrate, low-calorie diet that had led to his own dramatic weight loss.
, popularized one of the first weight loss diets in the 19th century.
One of the first dietitians was the English doctor George Cheyne. He himself was tremendously overweight and would constantly eat large quantities of rich food and drink. He began a meatless diet, taking only milk and vegetables, and soon regained his health. He began publicly recommending his diet for everyone suffering from obesity. In 1724, he wrote An Essay of Health and Long Life, in which he advises exercise and fresh air and avoiding luxury foods.
The Scottish military surgeon, John Rollo, published Notes of a Diabetic Case in 1797. It described the benefits of a meat diet for those suffering from diabetes, basing this recommendation on Matthew Dobson’s discovery of glycosuria in diabetes mellitus. By means of Dobson’s testing procedure (for glucose in the urine) Rollo worked out a diet that had success for what is now called type 2 diabetes.
The first popular diet was “Banting”, named after the English undertaker William Banting. In 1863, he wrote a booklet called Letter on Corpulence, Addressed to the Public, which contained the particular plan for the diet he had successfully followed. His own diet was four meals per day, consisting of meat, greens, fruits, and dry wine. The emphasis was on avoiding sugar, sweet foods, starch, beer, milk and butter. Banting’s pamphlet was popular for years to come, and would be used as a model for modern diets. The pamphlet’s popularity was such that the question “Do you bant?” referred to his method, and eventually to dieting in general. His booklet remains in print as of 2007.
The first weight-loss book to promote calorie counting, and the first weight-loss book to become a bestseller, was the 1918 Diet and Health: With Key to the Calories by American physician and columnist Lulu Hunt Peters.
Low-fat diets involve the reduction of the percentage of fat in one’s diet. Calorie consumption is reduced because less fat is consumed. Diets of this type include NCEP Step I and II. A meta-analysis of 16 trials of 2–12 months’ duration found that low-fat diets (without intentional restriction of caloric intake) resulted in average weight loss of 3.2 kg (7.1 lb) over habitual eating.
Low-carbohydrate diets such as Atkins and Protein Power are relatively high in protein and fats. Low-carbohydrate diets are sometimes ketogenic (i.e., they restrict carbohydrate intake sufficiently to cause ketosis).
Low-calorie diets usually produce an energy deficit of 500–1,000 calories per day, which can result in a 0.5 to 1 kilogram (1.1 to 2.2 pounds) weight loss per week. One of the most commonly used low-calorie diets is Weight Watchers. The National Institutes of Health reviewed 34 randomized controlled trials to determine the effectiveness of low-calorie diets. They found that these diets lowered total body mass by 8% in the short term, over 3–12 months. Women doing low-calorie diets should have at least 1,200 calories per day. Men should have at least 1,800 calories per day.
Very low calorie diets provide 200–800 calories per day, maintaining protein intake but limiting calories from both fat and carbohydrates. They subject the body to starvation and produce an average loss of 1.5–2.5 kg (3.3–5.5 lb) per week. “2-4-6-8”, a popular diet of this variety, follows a four-day cycle in which only 200 calories are consumed the first day, 400 the second day, 600 the third day, 800 the fourth day, and then totally fasting, after which the cycle repeats. These diets are not recommended for general use as they are associated with adverse side effects such as loss of lean muscle mass, increased risks of gout, and electrolyte imbalances. People attempting these diets must be monitored closely by a physician to prevent complications.
Detox diets claim to eliminate “toxins” from the human body rather than claiming to cause weight loss. Many of these use herbs or celery and other juicy low-calorie vegetables.
Religious prescription may be a factor in motivating people to adopt a specific restrictive diet. For example, the Biblical Book of Daniel (1:2-20, and 10:2-3) refers to a 10- or 21-day avoidance of foods (Daniel Fast) declared unclean by God in the laws of Moses. In modern versions of the Daniel Fast, food choices may be limited to whole grains, fruits, vegetables, pulses, nuts, seeds and oil. The Daniel Fast resembles the vegan diet in that it excludes foods of animal origin. The passages strongly suggest that the Daniel Fast will promote good health and mental performance.
Fasting is practiced in various religions. Examples include Lent in Christianity; Yom Kippur, Tisha B’av, Fast of Esther, Tzom Gedalia, the Seventeenth of Tamuz, and the Tenth of Tevet in Judaism.Muslims refrain from eating during the hours of daytime for one entire month, Ramadan, every year.
Details of fasting practices differ. Eastern Orthodox Christians fast during specified fasting seasons of the year, which include not only the better-known Great Lent, but also fasts on every Wednesday and Friday (except on special holidays), together with extended fasting periods before Christmas (the Nativity Fast), after Easter (the Apostles Fast) and in early August (the Dormition Fast). Members of The Church of Jesus Christ of Latter-day Saints (Mormons) generally fast for 24 hours on the first Sunday of each month. Like Muslims, they refrain from all drinking and eating unless they are children or are physically unable to fast. Fasting is also a feature of ascetic traditions in religions such as Hinduism and Buddhism. Mahayana traditions that follow the Brahma’s Net Sutra may recommend that the laity fast “during the six days of fasting each month and the three months of fasting each year” . Members of the Baha’i Faith observe a Nineteen Day Fast from sunrise to sunset during March each year.
Weight loss diets that manipulate the proportion of macronutrients (low-fat, low-carbohydrate, etc.) have been shown to be more effective than diets that maintain a typical mix of foods with smaller portions and perhaps some substitutions (e.g. low-fat milk, or less salad dressing). Extreme diets may, in some cases, lead to malnutrition.
Nutritionists also agree on the importance of avoiding fats, especially saturated fats, to reduce weight and to be healthier. They also agree on the importance of reducing salt intake because foods including snacks, biscuits, and bread already contain ocean-salt, contributing to an excess of salt daily intake.
MyPyramid Food Guidance System is the result of extensive research performed by the United States Department of Agriculture to revise the original Food Guide Pyramid. It offers a wide array of personalized options to help individuals make healthy food choices. It also provides advice on physical activity.
One of the most important things to take into consideration when either trying to lose or put on weight is output versus input. It is important to know the amount of energy your body is using every day, so that your intake fits the needs of one’s personal weight goal. Someone wanting to lose weight would want a smaller energy intake than what they put out. There is increasing research-based evidence that low-fat vegetarian diets consistently lead to healthy weight loss and management, a decrease in diabetic symptoms as well as improved cardiac health.
How the body eliminates fat
When the body is expending more energy than it is consuming (e.g. when exercising), the body’s cells rely on internally stored energy sources, such as complex carbohydrates and fats, for energy. The first source to which the body turns is glycogen (by glycogenolysis). Glycogen is a complex carbohydrate, 65% of which is stored in skeletal muscles and the remainder in the liver (totaling about 2,000 kcal in the whole body). It is created from the excess of ingested macronutrients, mainly carbohydrates. When glycogen is nearly depleted, the body begins lipolysis, the mobilization and catabolism of fat stores for energy. In this process, fats, obtained from adipose tissue, or fat cells, are broken down into glycerol and fatty acids, which can be used to generate energy. The primary by-products of metabolism are carbon dioxide and water; carbon dioxide is expelled through the respiratory system.
Weight loss groups
Some weight loss groups aim to make money, others work as charities. The former include Weight Watchers and Peertrainer. The latter include Overeaters Anonymous and groups run by local organizations.
These organizations’ customs and practices differ widely. Some groups are modelled on twelve-step programs, while others are quite informal. Some groups advocate certain prepared foods or special menus, while others train dieters to make healthy choices from restaurant menus and while grocery-shopping and cooking.
A 2008 study published in the American Journal of Preventive Medicine showed that dieters who kept a daily food diary (or diet journal), lost twice as much weight as those who did not keep a food log, suggesting that if you record your eating, you wouldn’t eat as many calories.
Possible weight loss effects of drinking water prior to meals
A 2009 review found that existing limited evidence suggested that encouraging water consumption and substituting energy-free beverages for energy-containing beverages (i.e., reducing caloric intake) may facilitate weight management. A 2009 article found that drinking 500 ml of water prior to meals for a 12-week period resulted in increased long-term weight reduction. (References given in main article.)
Lengthy fasting can be dangerous due to the risk of malnutrition and should be carried out only under medical supervision. During prolonged fasting or very low calorie diets the reduction of blood glucose, the preferred energy source of the brain, causes the body to deplete its glycogen stores. Once glycogen is depleted the body begins to fuel the brain using ketones, while also metabolizing body protein (including but not limited to skeletal muscle) to be used to synthesize sugars for use as energy by the rest of the body. Most experts believe that a prolonged fast can lead to muscle wasting, although some dispute this. The use of short-term fasting, or various forms of intermittent fasting have been used as a form of dieting to circumvent this issue.
While there are studies that show the health and medical benefits of weight loss, a study in 2005 of around 3000 Finns over an 18-year period showed that weight loss from dieting can result in increased mortality, while those who maintained their weight fared the best. Similar conclusion is drawn by other studies, and although other studies suggest that intentional weight loss has a small benefit for individuals classified as unhealthy, it is associated with slightly increased mortality for healthy individuals and the slightly overweight but not obese. This may reflect the loss of subcutaneous fat and beneficial mass from organs and muscle in addition to visceral fat when there is a sudden and dramatic weight loss.
Low carbohydrate versus low fat
Many studies have focused on diets that reduce calories via a low-carbohydrate (Atkins diet, Scarsdale diet, Zone diet) diet versus a low-fat diet (LEARN diet, Ornish diet). The Nurses’ Health Study, an observational cohort study, found that low carbohydrate diets based on vegetable sources of fat and protein are associated with less coronary heart disease. The same study also found no correlation (with multivariate adjustment) between animal fat intake and coronary heart disease (table 4). A long term study that monitored 43,396 Swedish women however suggests that a low carbohydrate-high protein diet, used on a regular basis and without consideration of the nature of carbohydrates or the source of proteins, is associated with increased risk of cardiovascular disease.
A meta-analysis of randomized controlled trials by the international Cochrane Collaboration in 2002 concluded that fat-restricted diets are no better than calorie-restricted diets in achieving long term weight loss in overweight or obese people. A more recent meta-analysis that included randomized controlled trials published after the Cochrane review found that low-carbohydrate, non-energy-restricted diets appear to be at least as effective as low-fat, energy-restricted diets in inducing weight loss for up to 1 year. These results can be understood because weight loss is mainly governed by daily caloric deficit and not by the particular foods eaten. However, when low-carbohydrate diets to induce weight loss are considered, potential favorable changes in triglyceride and high-density lipoprotein cholesterol values should be weighed against potential unfavorable changes in low-density lipoprotein cholesterol values.”
The Women’s Health Initiative Randomized Controlled Dietary Modification Trial found that a diet of total fat to 20% of energy and increasing consumption of vegetables and fruit to at least 5 servings daily and grains to at least 6 servings daily resulted in:
- no reduction in cardiovascular disease
- no statistically significant reduction in invasive breast cancer
- no reductions in colorectal cancer
Additional randomized controlled trials found that:
- A comparison of Atkins, Zone diet, Ornish diet, and LEARN diet in premenopausal women found the greatest benefit from the Atkins diet.
- The choice of diet for a specific person may be influenced by measuring the individual’s insulin secretion:
In young adults “Reducing glycemic load may be especially important to achieve weight loss among individuals with high insulin secretion.” This is consistent with prior studies of diabetic patients in which low carbohydrate diets were more beneficial.
The American Diabetes Association recommended a low carbohydrate diet to reduce weight for those with or at risk of Type 2 diabetes in its January 2008 Clinical Practice Recommendations.
Low glycemic index
“The glycemic index (GI) factor is a ranking of foods based on their overall effect on blood sugar levels. The diet based around this research is called the Low GI diet. Low glycemic index foods, such as lentils, provide a slower, more consistent source of glucose to the bloodstream, thereby stimulating less insulin release than high glycemic index foods, such as white bread.”
The glycemic load is “the mathematical product of the glycemic index and the carbohydrate amount”.
In a randomized controlled trial that compared four diets that varied in carbohydrate amount and glycemic index found complicated results:
- Diet 1 and 2 were high carbohydrate (55% of total energy intake)
- Diet 1 was high-glycemic index
- Diet 2 was low-glycemic index
- Diet 3 and 4 were high protein (25% of total energy intake)
- Diet 3 was high-glycemic index
- Diet 4 was low-glycemic index
Diets 2 and 3 lost the most weight and fat mass; however, low density lipoprotein fell in Diet 2 and rose in Diet 3. Thus the authors concluded that the high-carbohydrate, low-glycemic index diet was the most favorable.
A meta-analysis by the Cochrane Collaboration concluded that low glycemic index or low glycemic load diets led to more weight loss and better lipid profiles. However, the Cochrane Collaboration grouped low glycemic index and low glycemic load diets together and did not try to separate the effects of the load versus the index.
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In sum, there is little support for the notion that diets lead to lasting weight loss or health benefits.
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- Dieting at Curlie (based on DMOZ)
- A PBS Frontline interview with Prof. Walter Willett, Chair of Harvard’s nutrition department (2004)
- “Not All Calories Are Created Equal, Author Says”. Excerpt from Good Calories, Bad Calories and NPR interview with Gary Taubes and Dr. Ronald Krauss (2 November 2007).
- The food pyramid: Video lectures at the Harvard School of public health
- US News and World Report, Health: Eat Like Our Ancestors. An Interview with Harvard Psychology’s Deirdre Barrett 6/29/07
Dieting is the practice of eating (and drinking) in a regulated fashion to achieve a particular, short term objective. This is distinct from the more basic concept of “diet,” which addresses the longer term and more generic habit of nutritional consumption. For example, a purist vegan eats a diet completely devoid of animal products, including milk; but while this is a diet, it is not “dieting.”
The most common objective of dieting is loss of excess body fat. There are also special religious diets – observant Jews, for example, must not eat certain foods during Passover when special dietary rules are in effect; and other religious-based dietary restrictions apply throughout the year to Jews, Muslims, and Hindus, among others. Some diets are prescribed for particular medical reasons, such as sodium-free diets, bland diets and soft food diets. Some dieting is actually designed to promote increase of body fat and/or of muscular weight gain.
Types of Diets
There are several kinds of diets:
Weight-loss diets restrict the intake of specific foods, or food in general, or reduce body weight. This is what “fad diets” are marketed for. There is a (sometimes confusing) multitude of weight loss techniques, many of which are ineffective. What works for one person will not necessarily work for another, due to metabolic differences and lifestyle factors.
Certain religions (such as Judaism, Hinduism and Islam) impose strict restrictions on food choices and preparation, in accordance with edict and tradition.
Vegetarianism is typically adopted in pursuit of general good health, for spiritual or ethical reasons, when other food choices are not available, or as a matter of personal taste.
Anorexia and bulimia are psychological (and possibly neurological) disorders in which victims endanger their lives through dangerous diet patterns.
Many professional athletes impose weight-gain diets on themselves. For example, wrestlers may overeat in order to achieve a higher weight class. American Football players may try to “bulk up” through weight-gain diets in order to gain an advantage on the field with a higher mass.
Medical conditions often require the following of special diets. Each of these such diets will specifically include or exclude or regulate certain chemicals (and the foods that contain them). For example, a person who has diabetes is often on a diet designed to carefully manage their blood sugar level.
The practice of dieting in order to lose weight is ancient in its origins. Throughout the 17th and 18th centuries, physicians and patients regulated their food carefully, in order to prevent disease. In the 19th century, as the scientific classification of foods took shape, doctors and scientists began experimenting with targeted diets.
William Banting is one of the first people known to have successfully lost weight by dieting, circa 1863, by targeting carbohydrates. The low carbohydrate diet, sometimes marketed today as the Atkins Diet, remains popular today.
Scientific principles of weight loss:
A successful weight-loss diet requires that energy expenditure exceeds energy intake (from food). One must burn 14,500 kilojoules (3,500 Calories) more than one consumes to lose one pound (0.45 kilograms) or burn 37,000 kilojoules (9000 Calories) more than one consumes to lose one kilogram. (disputed — see talk page)
According to the principles of thermoregulation, humans are endotherms. We expend energy to maintain our blood temperature at body temperature, which is about 37 °C (98.6 °F). This is accomplished by metabolism and blood circulation, by shivering to stay warm, and by sweating to stay cool.
In addition to thermoregulation, humans expend energy keeping the vital organs (especially the lungs, heart and brain) functioning. Except when sleeping, our skeletal muscles are working, typically to maintain upright posture. The average work done just to stay alive is the basal metabolic rate, which (for humans) is about 1 watt per kilogram of body mass. Thus, an average man of 75 kilograms who just rests (or only walks a few steps) burns about 75 watts (continuously), or about 6,500 kilojoules (1,500 Calories) per day.
Physical exercise (with an example):
Physical exercise is an important complement to dieting in securing weight loss. Aerobic exercise is also an important part of maintaining normal good health, especially the muscular strength of the heart. To be useful, aerobic exercise requires maintaining a target heart rate of above 50 percent of one’s maximum heart rate for 30 minutes, at least 3 times a week. Brisk walking can accomplish this.
The ability of a few hours a week of exercise to contribute to weight loss can be overestimated. To illustrate, consider a 100-kilogram man who wants to lose 10 kilograms and assume that he eats just enough to maintain his weight (at rest), so that weight loss can only come from exercise. Those 10 kilograms converted to work are equivalent to about 350 megajoules. (We use an approximation of the standard 37 kilojoules or 9 Calories per gram of fat.) Now assume that his chosen exercise is stairclimbing and that he is 20 percent efficient at converting chemical energy into mechanical work (this is within measured ranges). To lose the weight, he must ascend 70 kilometers. A man of normal fitness (like him) will be tired after 500 meters of climbing (about 150 flights of stairs), so he needs to exercise every day for 140 days (to reach his target).
The minimum safe dietary energy intake (without medical supervision) is 75 percent of that needed to maintain basal metabolism. For our hypothetical 100-kilogram man, that minimum is about 5,700 kilojoules (1,300 Calories) per day. By combining daily aerobic exercise with a weight-loss diet, he would be able to lose 10 kilograms in half the time (70 days). Of course, the described regime is more rigorous than would be desirable or advisable for many persons. Therefore, under an effective but more manageable weight-loss program, losing 10 kilograms (about 20 pounds) may take as long as 6 months.
Fat loss versus muscle loss (and the importance of exercise and protein intake)
It is important to understand the difference between weight loss and fat loss. Weight loss typically involves the loss of fat, water and muscle. A dieter can lose weight without losing much fat. Ideally, overweight people should seek to lose fat and preserve muscle, since muscle burns more calories than fat. Generally, the more muscle mass one has, the higher one’s metabolism is, resulting in more calories being burned, even at rest. Since muscles are denser, muscle loss results in little loss of physical bulk compared with fat loss. To determine whether weight loss is due to fat, various methods of measuring body fat percentage have been developed.
Muscle loss during weight loss can be restricted by regularly lifting weights (or doing push-ups and other strength-oriented calisthenics) and by maintaining sufficient protein intake. According to the National Academy of Sciences, the Dietary Reference Intake for protein is “0.8 grams per kilogram of body weight for adults.”
Those on low-carbohydrate diets, and those doing particularly strenuous exercise, may wish to increase their protein intake. However, there may be risks involved. According to the American Heart Association, excessive protein intake may cause liver and kidney problems and may be a risk factor for heart disease .
Actual energy obtained from food
The energy humans get from food is limited by the efficiency of digestion and the efficiency of utilization. The efficiency of digestion is largely dependent on the type of food being eaten. Poorly chewed seeds are poorly digested. Refined sugars and fats are absorbed almost completely. Despite the claims of certain popular diets, chewing and digesting does not use a substantial amount of the energy offered by any food (that anyone would want to eat). Even celery, known for being low in caloric value, contains enough sugars (including sucrose, glucose and galactose) to easily compensate for the cost of (energy invested in) chewing it. (See Food & Nutrition Information Center.}
The efficiency of energy utilization by skeletal muscles is around 20 percent. That is, of the chemical energy used, 20 percent does work and 80 percent creates heat.
Humans require essential nutrients from 5 broad classes: proteins, fats, carbohydrates, vitamins and minerals. Essential amino acids (protein) are required for cell, especially muscle, construction. Essential fatty acids are required for brain and cell wall construction. Vitamins and minerals are essential for many functions.
Any diet that fails to meet minimum nutritional requirements can threaten general health (and physical fitness in particular). If a person is not well enough to be active, weight loss and good quality-of-life will be unlikely.
The National Academy of Sciences and the World Health Organization publish guidelines for dietary intakes of all known essential nutrients.
Sometimes dieters will take excessive amounts of vitamin and mineral supplements. While this is usually harmless, some nutrients are notably dangerous. Men (and women who don’t menstruate) need to be wary of iron poisoning. Retinol (oil-soluble vitamin A) is toxic in large doses.
A sensible weight-loss diet is a normal balanced diet; it just comes with smaller portions. Extreme diets (based on caprice or obsession) will likely lead to malnutrition.
How the body gets rid of fat
All body processes require energy to run properly. When the body is expending more energy than it is taking in (e.g. when exercising), body cells rely on internally stored energy sources, like complex carbohydrates and fats, for energy. The first source the body turns to is glycogen, which is a complex carbohydrate created by the body. When that source is nearly depleted, the body begins lipolysis, the metabolism of fat for energy. In this process, fats, obtained from fat cells, are broken down into glycerol and fatty acids, which can be used to make energy. The primary by-products of metabolism are carbon dioxide and water; carbon dioxide is expelled through the respiratory system. Fats are also secreted by the sebaceous glands (in the skin).
Psychological aspects of weight-loss dieting:
Diets affect the “energy in” component of the energy balance by limiting or altering the distribution of foods. Techniques that affect the appetite can limit energy intake by affecting the desire to overeat.
Consumption of low-energy, fiber-rich foods, such as non-starchy vegetables, is effective in obtaining satiation (the feeling of “fullness”). Exercise is also useful in controlling appetite. (Extreme physical fatigue, such as experienced by soldiers and mountain climbers, can make eating a difficult chore.)
The use of drugs to control appetite is (potentially) dangerous. Stimulants are often taken as a means to ignore (normal, healthy) hunger by people who are not actually overweight.
Habitual or emotional eating is a common problem. Sufferers often turn to self-help books, hypnosis and group therapy. While these sources can sometimes be of assistance, dieters must beware. Some “diet gurus” are charlatans, others are well-meaning but focus on psychology or philosophy at the expense of practical solutions. Diets designed to appeal to people emotionally are often either very difficult to follow (i.e., too strict) or useless (i.e., too lenient).
Weight loss groups:
There exist both profit-oriented and non-profit weight loss organizations who assist people in their weight loss efforts. Examples of the former include Weight Watchers and Jenny Craig; examples of the latter include Overeaters Anonymous, as well as a multitude of non-branded support groups run by local churches, hospitals, and like-minded individuals.
These organizations’ customs and practices differ widely. Some groups are modelled on twelve-step programs, while others are quite informal. Some groups advocate certain prepared foods or special menus, while others train dieters to make healthy choices from restaurant menus and while grocery-shopping and cooking.
Most groups leverage the power of group meetings to provide counseling, emotional support, problem-solving, and useful information.
Popular Weight-Loss diets:
Popular diets (sometimes pejoratively called “fad diets”) usually derive their popularity from the personalities of their proponents. These proponents include “diet gurus” and celebrity converts. “Diet books” are the primary means of communicating the specifics of popular diets.
Most popular diets experience short-lived popularity, partly because new diet books are continuously being published.
Judging the effectiveness (and nutritional merit) of popular diets can be especially difficult. Diet proponents often locate medical professionals to back up their work. And some diets are so controversial that they divide the medical community.
Many popular diets advocate the combination a specific technique (such as eliminating a certain food, or eating only certain combinations of foods) with reduced caloric intake, with the goal being to accelerate weight loss. Others ignore traditional science altogether.
Low-fat diets were popular during the 1980s and 1990s, encouraging people to eat foods low in fat (or without fat altogether) and instead eat foods high in carbohydrates.
Unfortunately, the general public came to believe, partly due to information from low-fat diet proponents, that carbohydrates were “energy food” and that only fat made people fat. This led to excessive consumption of low-fat foods rich in refined carbohydrates (notably corn syrup), which lead some people to gain more weight.
Some low-fat diets were healthier, focusing on consumption of whole grains, vegetables and lean meats. (See Pritikin diet.) But even these diets did not recognize the importance of essential fatty acids.
Atkins (low-carbohydrate diet):
The Atkins Diet is a very popular diet. Dr. Robert Atkins’ concept, somewhat exaggerated by the media, that a person can lose weight whilst gorging on meat, has captured the public’s imagination. The success of those who tried the diet varied depending on the degree they adhered to the long term stages of the diet structure. The Atkins diet was originally designed for diabetes patients who wanted to manage their insulin levels more effectively. The diet was also embraced by those seeking a diet that allows eating to satiation.
Atkins discourages refined carbohydrate intake and encourages protein intake, especially in the form of meat. The diet encourages the consumption of fruits and non-starchy vegetables for the provision of fiber and nutrients; it takes a somewhat neutral stand on fat intake.
Many people experience rapid initial weight loss on Atkins, some of which is due to depletion of glycogen stores in the liver. (Glycogen in the body is associated with several times its weight in water.)
Low carbohydrate diets have been shown to reduce the fasting levels of triglycerides. Elevated triglycerides are a demonstrated risk factor for heart disease. (Low-fat diets also reduce fasting levels of triglycerides.)
A low-carbohydrate diet may not be suitable as a weight-maintenance diet (long-term). The products of fat metabolism (lipolysis) and protein metabolism (gluconeogenesis) include ketones.
Since the advent of controversial diets such as Atkins, various diets that stress the eating habits of “natural humans” have been developed. The Evolution Diet explains “what and how we were designed to eat”; the Paleolithic Diet imitates the way people ate during the Stone Age. These eating plans include basically natural foods (those not processed by humans). Whereas the Paleolithic Diet exludes milk and grain-foods, The Evolution Diet excludes man-made ingredients like partially hydrogenated oils but allows some processed foods like whole-grain crackers and dairy products.
There is a growing body of evidence that vegetarian diets can prevent obesity and lower disease risks.
According to the American Dietetic Association, “Vegetarians have been reported to have lower body mass indices than nonvegetarians, as well as lower rates of death from ischemic heart disease; vegetarians also show lower blood cholesterol levels; lower blood pressure; and lower rates of hypertension, type 2 diabetes, and prostate and colon cancer.”
Vegans on average weigh 10 percent less than non-vegetarians. And in a year-long study comparing Dean Ornish’s vegetarian diet to Weight Watchers, The Zone Diet, and The Atkins Diet, subjects on Dean Ornish’s diet achieved the most weight loss (on average).
Very Low Calorie Diet:
The Very Low Calorie Diet (VLCD) is a prescribed diet for obese patients. Daily intake consists of three milkshake-like formula drinks (made with powder concentrate and water), which supply about 2000 kilojoules (500 Calories) and all necessary vitamins and minerals.
There are risks to this diet. A patient who drinks more formula than allowed can get too much iron and selenium. Constipation is a problem: extra water and (fiber) laxatives may be required. Immune response may be compromised.
VLCD should only be used for dieting when a patient’s body mass index exceeds 30. The diet requires regular consultation between patient and doctor.
VLCD can be very successful when used over a 6-12 week period. As with all starvation diets, metabolism will fall. A sensible diet-and-exercise plan must follow cessation of VLCD, or weight will be gained back.
Dangers of weight loss dieting
Strange or extreme diets can be very dangerous, and they are often ineffective. If one seeks the sensible and popular ideal of being lean and athletic, then starvation diets are counterproductive.
There are many diet pills for sale, some which are associated with comprehensive dietary programs. Many such pills, including many of those containing vitamins and minerals, are not effective for losing weight.
Some drugs enable short-term weight loss, usually with unpleasant and potentially dangerous side effects. The drugs include (physiologically active) herbal products available at health food stores, as well as over-the-counter (OTC) and prescribed medications provided by doctors and pharmacists.
Typically these drugs fall into two classes: diuretics to induce water-weight loss and stimulants (such as ephedrine) to increase heart rate and reduce appetite. Both classes of drugs can cause kidney and liver damage, and stimulants can cause sudden heart attacks and addiction.
Yo-yo dieting is defined by alternating periods of feast and famine (that the dieter deliberately undertakes). It is a particularly ineffective method of sustaining weight loss.
The human body responds to starvation by decreasing metabolism. When food is again available, it is stored immediately as fat. This survival mechanism, while a useful response to genuine food scarcity, leaves the yo-yo dieter feeling lethargic and fatigued (and defeated).
Metabolism can be restored to a higher level with exercise and a sensible weight-loss diet. This diet is defined by the minimum safe daily caloric intake of 75 percent of the basal metabolic rate or 4200 kilojoules (1000 Calories), whichever is greater. (Those eating less should do so only under medical supervision. Parents and guardians should consult medical professionals before placing their children on any type of diet.)
Once an ideal weight is attained, a weight-maintenance diet is essential. This requires limiting excess caloric intake and making small changes in caloric intake in response to physical observations (of one’s weight and appearance).
Scientific analysis of the dangers of fasting (and discussion of partial fasting with protein supplementation)
While anyone can lose weight by fasting (temporarily stopping one’s food intake), it is a dangerous practice. When concentration camp survivors, who involuntarily suffered famine as a result of horrendous living conditions, were examined by doctors, what little weight they had was mostly fat, with practically no muscle.
The muscle loss is partly due to the fact that the brain cannot rely completely on fat for fuel. The brain usually reserves ketones for lipid synthesis but will use ketones (from fat) for some energy once levels rise during carbohydrate shortages or starvation, but it must get at least 15 percent of its energy from glucose, and it takes a much greater percentage than this early in a fast before the switch to ketones for most energy needs. Glucose can only be synthesized from proteins, glycerol and carbohydrates.
The body stores carbohydrates as fat and as glycogen in the muscles and the liver; glycogen is used to make glucose. Glycogen stores (from carbohydrates) can only last a couple days (during starvation). (In fact, marathon runners experience a shortage of easily-available glycogen after only 2 hours: they speak of “hitting the wall”.)
Because fasts, very low calorie diets (VLCD), and low-carbohydrate diets restrict the intake of carbohydrates, glucose must be obtained from protein. If dietary protein is insufficient, internal sources will be obtained: autolysis and muscle wasting occurs. (The conversion of amino acids to glucose is called gluconeogenesis.)
A very low calorie diet that restricts all carbohydrates and non-essential fats, while providing just enough dietary protein to prevent muscle loss, is termed a “protein sparing modified fast” (PSMF).
After experimentation, it was found that a protein intake of 1 to 1.5 grams of protein per kilogram of ideal bodyweight (lean body mass or LBM) prevented the loss of body protein. A somewhat “safer” intake of .8 to 1.2 grams of protein per pound of LBM is often recommended. (More active persons and those taking less protein must compensate by consuming at least some carbohydrates.)
Thus, PSMF allows for rapid fat loss due to the severe caloric deficit that is created when nearly all carbohydrates and fats are removed from the diet. This extreme dieting technique has many potential hazards, such as hormonal changes and rapid metabolic slowdown. PSMF is sometimes used by bodybuilders to “get cut” (lose fat to expose muscle) just before competitions.
Dieting, especially extreme food-intake reduction, can have the following side effects:
- Prolonged hunger
- Reduced sex drive
- Sinus problems (especially post-nasal drip)
- Muscle loss
- Bloodshot eyes
Information about specific Diet:
An individual’s diet is the sum of food and drink that he or she habitually consumes. Dieting is the practice of attempting to achieve or maintain a certain weight through diet. People’s dietary choices are often affected by a variety of factors, including ethical and religious beliefs, clinical need, or a desire to control weight.
Not all diets are considered healthy. Some people follow unhealthy diets through habit, rather than through a conscious choice to eat unhealthily. Terms applied to such eating habits include “junk food diet” and “Western diet”. Many diets are considered by clinicians to pose significant health risks and minimal long-term benefit. This is particularly true of “crash” or “fad” diets – short-term weight-loss plans that involve drastic changes to a person’s normal eating habits.
Only diets covered on Wikipedia are listed.
A vegetarian diet is one which excludes meat. Vegetarians also avoid food containing by-products of animal slaughter, such as animal-derived rennet and gelatin.
- Fruitarian diet: A diet which predominantly consists of raw fruit.
- Lacto vegetarianism: A vegetarian diet that includes certain types of dairy, but excludes eggs and foods which contain animal rennet. A common diet among followers of several religions, including Hinduism, Sikhism and Jainism, based on the principle of Ahimsa (non-harming).
- Ovo vegetarianism: A vegetarian diet that includes eggs, but excludes dairy.
- Ovo-lacto vegetarianism: A vegetarian diet that includes eggs and dairy.
- Vegan diet: In addition to the abstentions of a vegetarian diet, vegans do not use any product produced by animals, such as eggs, dairy products, or honey. The vegan philosophy and lifestyle is broader than just the diet and also includes abstaining from using any products tested on animals and often campaigning for animal rights.
- Semi-vegetarianism: A predominantly vegetarian diet, in which meat is occasionally consumed.
- Kangatarian: A diet originating from Australia. In addition to foods permissible in a vegetarian diet, kangaroo meat is also consumed.
- Pescetarian diet: A diet which includes fish but not other meats.
- Plant-based diet: A broad term to describe diets in which animal products do not form a large proportion of the diet. Under some definitions a plant-based diet is fully vegetarian; under others it is possible to follow a plant-based diet whilst occasionally consuming meat.
- Pollotarian: someone who eats chicken or other poultry, but not meat from mammals, often for environmental, health or food justice reasons.
- Pollo-pescetarian: someone who eats both poultry and fish/seafood, though no meat from mammals.
Weight control diets
A desire to lose weight is a common motivation to change dietary habits, as is a desire to maintain an existing weight. Many weight loss diets are considered by some to entail varying degrees of health risk, and some are not widely considered to be effective. This is especially true of “crash” or “fad” diets.
Many of the diets listed below could fall into more than one subcategory. Where this is the case, it is noted in that diet’s entry.
- Intermittent fasting: Cycling between non-fasting and fasting as a method of calorie restriction.
- Body for Life: A calorie-control diet, promoted as part of the 12-week Body for Life program.
- Cookie diet: A calorie control diet in which low-fat cookies are eaten to quell hunger, often in place of a meal.
- The Hacker’s Diet: A calorie-control diet from The Hacker’s Diet by John Walker. The book suggests that the key to reaching and maintaining the desired weight is understanding and carefully monitoring calories consumed and used.
- Nutrisystems Diet: The dietary element of the weight-loss plan from Nutrisystem, Inc. Nutrisystem distributes low-calorie meals, with specific ratios of fats, proteins and carbohydrates.
- Weight Watchers diet: Foods are assigned point values; dieters can eat any food with a point value provided they stay within their daily point limit.
Very low calorie diets
A very low calorie diet is consuming fewer than 800 calories per day. Such diets are normally followed under the supervision of a doctor. Zero-calorie diets are also included.
- Inedia (breatharian diet): A diet in which no food is consumed, based on the belief that food is not necessary for human subsistence.
- KE diet: A diet in which an individual feeds through a feeding tube and does not eat anything.
- Atkins diet: A low-carbohydrate diet, popularized by nutritionist Robert Atkins in the late-20th and early-21st centuries. Proponents argue that this approach is a more successful way of losing weight than low-calorie diets; critics argue that a low-carb approach poses increased health risks. The Atkins diet consists of four phases (Induction, Balancing, Fine-Tuning and Maintenance) with a gradual increase in consumption of carbohydrates as the person goes through the phases.
- Dukan Diet: A multi-step diet based on high protein and limited carbohydrate consumption. It starts with two steps intended to facilitate short term weight loss, followed by two steps intended to consolidate these losses and return to a more balanced long-term diet.
- South Beach Diet: Diet developed by the Miami-based cardiologist Arthur Agatston, M.D., who says that the key to losing weight quickly and getting healthy isn’t cutting all carbohydrates and fats from your diet. It’s learning to choose the right carbs and the right fats.
- Stillman diet
- McDougall’s starch diet is a high calorie, high fiber, low fat diet that is based on starches such as potatoes, rice, and beans which excludes all animal foods and added vegetable oils. John A. McDougall draws on historical observation of how many civilizations around the world throughout time have thrived on starch foods.
Crash diet and fad diet are general terms. They describe diet plans which involve making extreme, rapid changes to food consumption, but are also used as disparaging terms for common eating habits which are considered unhealthy. Both types of diet are often considered to pose health risks. Many of the diets listed here are weight-loss diets which would also fit into other sections of this list. Where this is the case, it will be noted in that diet’s entry.
- Beverly Hills Diet: An extreme diet which has only fruits in the first days, gradually increasing the selection of foods up to the sixth week.
- Cabbage soup diet: A low-calorie diet based on heavy consumption of cabbage soup. Considered a fad diet.
- Grapefruit diet: A fad diet, intended to facilitate weight loss, in which grapefruit is consumed in large quantities at meal times.
- Israeli Army diet: An eight-day diet. Only apples are consumed in the first two days, cheese in the following two days, chicken on days five and six, and salad for the final two days. Despite what the name suggests, the diet is not followed by Israel Defense Forces. It is considered a fad diet.
- Subway diet: A crash diet in which a person consumes Subway sandwiches in place of higher calorie fast foods. Made famous by former obese student Jared Fogle, who lost 245 pounds after replacing his meals with Subway sandwiches as part of an effort to lose weight.
- Western dietary pattern: A diet consisting of food which is most commonly consumed in developed countries. Examples include meat, white bread, milk and puddings. The name is a reference to the Western world.
Detox diets involve either not consuming or attempting to flush out substances that are considered unhelpful or harmful. Examples include restricting food consumption to foods without colorings or preservatives, taking supplements, or drinking large amounts of water. The latter practice in particular has drawn criticism, as drinking significantly more water than recommended levels can cause hyponatremia.
- Juice fasting: A form of detox diet, in which nutrition is obtained solely from fruit and vegetable juices. The health implications of such diets are disputed.
- Master Cleanse: A form of juice fasting.
Some people’s dietary choices are influenced by their religious, spiritual or philosophical beliefs.
- Buddhist diet: While Buddhism does not have specific dietary rules, some buddhists practice vegetarianism based on a strict interpretation of the first of the Five Precepts.
- Hindu and Jain diets: Followers of Hinduism and Jainism may follow lacto vegetarian diets (though most do not, as some Hindu festivals require meat to be eaten), based on the principle of ahimsa (non-harming).
- Islamic dietary laws: Muslims follow a diet consisting solely of food that is halal – permissible under Islamic law. The opposite of halal is haraam, food that is Islamically Impermissible. Haraam substances include alcohol, pork, and any meat from an animal which was not killed through the Islamic method of ritual slaughter (Dhabiha).
- I-tal: A set of principles which influences the diet of many members of the Rastafari movement. One principle is that natural foods should be consumed. Some Rastafarians interpret I-tal to advocate vegetarianism or veganism.
- Kosher diet: Food permissible under Kashrut, the set of Jewish dietary laws, is said to be Kosher. Some foods and food combinations are non-Kosher, and failure to prepare food in accordance with Kashrut can make otherwise permissible foods non-Kosher.
- Seventh-day Adventist: Seventh-day Adventists combine the Kosher rules of Judaism with prohibitions against alcohol and caffeinated beverages and an emphasis on whole foods. About half of Adventists are lacto-ovo-vegetarians.
- Word of Wisdom: The name of a section of the Doctrine and Covenants, a book of scripture accepted by members of The Church of Jesus Christ of Latter-day Saints. Dietary advice includes (1) wholesome plants “in the season thereof”, (2) eating meat sparingly and only “in times of winter, or of cold, or famine”, and (3) grain as the “staff of life”.
Diets followed for medical reasons
People’s dietary choices are sometimes affected by intolerance or allergy to certain types of food. There are also dietary patterns that might be recommended, prescribed or administered by medical professionals for people with specific medical needs.
- Diabetic diet: An umbrella term for diets recommended to people with diabetes. There is considerable disagreement in the scientific community as to what sort of diet is best for people with diabetes.
- DASH diet (Dietary Approaches to Stop Hypertension): A recommendation that those with high blood pressure consume large quantities of fruits, vegetables, whole-grains and low fat dairy foods as part of their diet, and avoid sugar sweetened foods, red meat and fats. Promoted by the US Department of Health and Human Services, a United States government organisation.
- Elemental diet: A medical, liquid-only diet, in which liquid nutrients are consumed for ease of ingestion.
- Elimination diet: A method of identifying foods which cause a person adverse effects, by process of elimination.
- Gluten-free diet: A diet which avoids the protein gluten, which is found in barley, rye and wheat. It is a medical treatment for gluten-related disorders, which include coeliac disease, non-celiac gluten sensitivity, gluten ataxia, dermatitis herpetiformis and wheat allergy.
- Gluten-free, casein-free diet: A gluten-free diet which also avoids casein, a protein commonly found in milk and cheese.
- Healthy kidney diet: This diet is for those impacted with chronic kidney disease, those with only one kidney who have a kidney infection and those who may be suffering from some other kidney failure. This diet is not the dialysis diet, which is something completely different. The healthy kidney diet restricts large amounts of protein which are hard for the kidney to break down but especially limits: potassium and phosphorus-rich foods and beverages. Liquids are often restricted as well—not forbidden, just less of.
- Ketogenic diet: A high-fat, low-carb diet, in which dietary and body fat is converted into energy. It is used as a medical treatment for refractory epilepsy.
- Liquid diet: A diet in which only liquids are consumed. May be administered by clinicians for medical reasons, such as after a gastric bypass or to prevent death through starvation from a hunger strike.
- Specific carbohydrate diet: A diet that aims to restrict the intake of complex carbohydrates such as found in grains and complex sugars. It is promoted as a way of reducing the symptoms of irritable bowel syndrome (IBS), Crohn’s disease, ulcerative colitis, coeliac disease, and autism.
- Alkaline diet: The avoidance of relatively acidic foods – foods with low pH levels – such as grains, dairy, meat, sugar, alcohol, caffeine and fungi. Proponents believe such a diet may have health benefits; critics consider the arguments to have no scientific basis.
- Blood type diet: A diet based on a belief that people’s diets should reflect their blood types.
- Eat-clean diet: Focusses on eating foods without preservatives, and on mixing lean proteins with complex carbohydrates.
- Fit for Life diet: Recommendations include not combining protein and carbohydrates, not drinking water at meal time, and avoiding dairy foods.
- Food combining diet: A nutritional approach where certain food types are deliberately consumed together or separately. For instance, some weight control diets suggest that proteins and carbohydrates should not be consumed in the same meal.
- Gerson therapy: A form of alternative medicine, the diet is low salt, low fat and vegetarian, and also involves taking specific supplements. It was developed by Max Gerson, who claimed the therapy could cure cancer and chronic, degenerative diseases. These claims have not been scientifically proven, and the American Cancer Society claims that elements of the therapy have caused serious illness and death.
- The Graham Diet: A vegetarian diet which promotes whole-wheat flour and discourages the consumption of stimulants such as alcohol and caffeine. Developed by Sylvester Graham in the 19th century.
- Hay diet: A food-combining diet developed by William Howard Hay in the 1920s. Divides foods into separate groups, and suggests that proteins and carbohydrates should not be consumed in the same meal.
- High-protein diet: A diet in which high quantities of protein are consumed with the intention of building muscle. Not to be confused with low-carb diets, where the intention is to lose weight by restricting carbohydrates.
- High residue diet: A diet in which high quantities of dietary fiber are consumed. High-fiber foods include certain fruits, vegetables, nuts and grains.
- Inuit diet: Inuit people traditionally consume food that is fished, hunted or gathered locally; predominantly meat and fish.
- Jenny Craig: A weight-loss program from Jenny Craig, Inc. It includes weight counselling among other elements. The dietary aspect involves the consumption of pre-packaged food produced by the company.
- Locavore diet: a neologism describing the eating of food that is locally produced, and not moved long distances to market.
- Low carbon diet: Consuming food which has been produced, prepared and transported with a minimum of associated greenhouse gas emissions. An example of this was explored in the book 100-Mile Diet, in which the authors only consumed food grown within 100 miles of their residence for a year. People who follow this type of diet are sometimes known as locavores.
- Low-fat diet
- Low glycemic index diet
- Low-protein diet
- Low sodium diet
- Low-sulfur diet
Some common macrobiotic ingredients
- Macrobiotic diet: A diet in which processed food is avoided. Common components include grains, beans and vegetables.
- Mediterranean diet: A diet based on habits of some southern European countries. One of the more distinct features is that olive oil is used as the primary source of fat.
- MIND diet: combines the portions of the DASH diet and the Mediterranean diet. The diet is intended to reduce neurological deterioration such as Alzheimer’s disease.
- Montignac diet: A weight-loss diet characterised by consuming carbohydrates with a low glycemic index.
- Negative calorie diet: A claim by many weight-loss diets that some foods take more calories to digest than they provide, such as celery. The basis for this claim is disputed.
- Okinawa diet: A low-calorie diet based on the traditional eating habits of people from the Ryukyu Islands.
- Omnivore: An omnivore consumes both plant and animal-based food.
- Organic food diet: A diet consisting only of food which is organic – it has not been produced with modern inputs such as chemical fertilizers, genetic modification, irradiation or food additives.
- Paleolithic diet: Can refer either to the eating habits of humans during the Paleolithic era, or of modern dietary plans purporting to be based on these habits.
- Prison loaf: A meal replacement served in some United States prisons to inmates who are not trusted to use cutlery. Its composition varies between institutions and states, but as a replacement for standard food, it is intended to provide inmates with all their dietary needs.
- Pritikin Program for Diet and Exercise: A diet which focusses on the consumption of unprocessed food.
- Raw foodism: A diet which centres on the consumption of uncooked and unprocessed food. Often associated with a vegetarian diet, although some raw food dieters do consume raw meat.
- Scarsdale Medical Diet
- Shangri-La Diet
- Slimming World diet
- Slow-carb diet
- Smart For Life
- Sonoma diet: A diet based on portion control and centered around consuming “power foods”
- SparkPeople diet
- Sugar Busters!: Focuses on restricting the consumption of refined carbohydrates, particularly sugars.
- Tongue Patch Diet: Stitching a Marlex patch to the tongue to make eating painful.
- Zone diet: A diet in which a person attempts to split calorie intake from carbohydrates, proteins and fats in a 40:30:30 ratio.
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