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.

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.

Vegetarian diet

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).

Natural Diets

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.

Atkins (low-carbohydrate 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.
Note: Any successful weight-loss diet will cause some acidosis; symptoms range from mild fatigue to severe joint pain. Acidosis can be controlled by drinking water (in large amounts) and taking antacid supplements (or eating vegetables grown in alkaline soil).

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.
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.

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.