Weight Loss Most typically, "dieting" means eating in a carefully planned way in an attempt to reduce excess body fat and decrease bodily measurements, such as clothing size. There exist 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. Scientific principles surrounding dieting Successful weight loss diet is all about energy in versus energy out. If a person takes in fewer calories than he or she expends over a period of time, the person may burn fat and subsequently lose weight. 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. This can be attempted by focusing on foods that are filling, through the use of certain appetite-suppressing drugs, or through activities such as mild exercise, that affect appetite. Other techniques address habitual or emotional eating. Affecting the energy out component is the focus of fitness and exercise programs. These might also be included in a comprehensive "diet." Dieting in order to lose weight does just that -- you lose weight, water, some fat and muscles. Since muscles are denser, you lose a lot of weight, but little in size. Fat is bulkier, so a three pound fat loss can cause a size loss. To lose a pound of fat, one must create a caloric deficit of approximately 3,500 calories; therefore, if a person creates a deficit of 500 calories per day, the person will lose approximately 1 pound of fat per week. Muscle-loss during weight-loss can be restricted by regularly lifting weights and by a high protein intake. (It is said that 0.8 to 1.0 g of protein per pound of body weight (1.76 to 2.20 g per kg) per day is sufficient.) A ketogenic diet is often very effective in lowering body-fat levels whilst maintaining or even increasing muscle mass. 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 and a multitude of non-branded support groups run by local churches, hospitals, or like-minded individuals.) These organizations' customs and practices differ widely, but most all of them leverage the power of group meetings with regards to counseling, emotional support, problem-solving, and the passing along of useful information. Some advocate certain prepared food or special menus, while others train how to make healthy choices from menus and while grocery-shopping. Fad diets Many 'fad' diets become widely popular for a short period of time, only to fade out. Although some fade from popularity due to being ineffective, some merely lose the public's interest. Judging their nutritional merit can be especially difficult given that most diet proponents locate medical professionals to back up their work. Examples of such fads include the grapefruit diet, low-fat diets, and Atkins. Most fad diets overlook the basic nutritional idea of energy balance discussed in greater detail above. The energy you take in (in the form of calories in food, whether fat, protein, or carbohydrate) must be less than the energy you burn in order to lose weight, so that your body burns fat to make up the energy deficit. If you take in more energy than you burn, your body will tend to store this excess energy as fat. Grapefruit diet On the grapefruit diet, the consumption of grapefruit with each meal was said to increase the metabolic rate, burning fat and enabling rapid weight loss. The grapefruit diet was eventually found to be entirely ineffective. Low-fat diets Low-fat diets were popular during the '80s and '90s, encouraging people to eat foods low in fat (or without fat altogether) and instead eat foods high in carbohydrates. The diet worked on the principle that of the three main macro-nutrients (fat, carbohydrates and protein), only fat was the one which would cause weight-gain. This failed as people ended up eating excessive amounts of low-fat foods rich in carbohydrates, and so did not lose much weight, or even gained it due to the energy from the carbohydrates. Atkins Atkins encourages controlling carbohydrate intake, and encouraged meats, nuts, unsweetened fruits, berries and green vegetables. This causes rapid weight loss for many people, although it continues to be disputed whether this is due to a metabolic advantage of ketosis, as Atkins claimed. Some of the initial rapid weight loss is due to depletion of glycogen stores in the liver. Glycogen must be associated with several times its weight of water in the body. Low carbohydrate diets have been shown to reduced the fasting levels of triglycerides. Elevated triglycerides are a demonstrated risk factor for heart disease and also account for part of the risk of low density cholesterol due to their associated worse particle size profile. Any successful diet for losing weight will cause some ketosis, since ketones are produced when the body is using fat energy to synthesize glucose (gluconeogenesis) during the long overnight fast (sleep). Elevated levels of fasting triglycerides (TGs) are the product of de novo lipogenesis (synthesis of new fats) from glucose substrate. If the liver was engaged in gluconeogenesis from fat, and synthesizing fat from glucose at the same time, this would be a futile cycle, and a fantastic way to waste energy and lose weight. For most of human history, it has been important to survival to avoid such inefficiency, so the body switches modes to avoid this futile cycle. This explains the dramatic reductions in fasting TGs seen in many low carbohydrate dieters. Atikins is not strictly a fad diet, since it is an approach that is still quite popular.
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