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. Some diets are so controversial that they divide the medical community.
Many popular diets advocate the combination of 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
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. 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 high consumption of low-fat foods high in refined carbohydrates (notably corn syrup), which may have contributed towards increased weight gain as carbohydrates (particularly refined carbohydrates) have a low nutrient density and high in calories. Some low-fat diets like the Pritikin diet focus on whole grains, vegetables and lean meats.
The Atkins diet was developed by Dr. Robert Atkins' and intended to control blood sugar by reducing the number of carbohydrates consumed (particularly refined carbohydrates) while replacing them with significant quantities of fat and protein.
The Atkins diet was originally designed for diabetes patients who wanted to manage their insulin levels more effectively. The short-term changes experienced by individuals on the Atkins diet included some rapid weightloss as the body's glycogen stores were depleted, reduced fasting levels of triglycerides and an increase in blood-bound ketones. The diet also caused acidosis and mild fatigue.
Since the advent of controversial diets such as Atkins, various diets that stress the eating habits of "natural humans" have been developed. 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 excludes milk and grain-foods, The Evolution Diet excludes human-made ingredients such as partially hydrogenated oils but allows some processed foods such as whole-grain crackers and dairy products.
Anthropologists who focus their research on human evolution, however, are quick to point out that the diet of Paleolithic peoples was most likely opportunistic. That is, these early humans would most likely eat whatever edible foods were available at any given moment in that particular area (e.g. vegetables, termites, meat) and not restrict their intake of any food. Until recent human history, starvation has been a far greater threat than over-consumption.
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."
Vegetarians 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 The Atkins Diet achieved the most weight loss (on average). Strict vegetarian diets like veganism may result in certain vitamin and mineral deficiencies if attention isn't paid to nutrition.
Weight Watchers has two programs. The program offers a wide variety and foods. Each food has a point value. They encourage a well rounded diet, low in fat and high in fruits and vegetables. The core plan focuses more on portion control and natural foods. According to Weight Watchers, the act of keeping track of what one eats is very helpful in reducing overeating or eating for reasons other than hunger.
VERY LOW CALORIE DIET
The very low calorie diet (VLCD) is a diet prescribed to morbidly obese patients. Daily intake consists of three milkshake-like formula drinks providing all necessary vitamins and minerals but supply only about 2000 kilojoules (500 calories). VLCD can potentially produce constipation, gallstones and iron and selenium overdose.