In the context of physical health, weight loss is the process of losing body weight, usually by losing fat. To achieve healthy weight loss, most experts recommend a combination of healthy eating patterns and regular physical exercise. Some people try to lose weight by using drugs such as fenfluoramine, nicotine or cocaine (see Anti-obesity drugs), herbs such as ephedra, or surgery such as liposuction. A loss of weight can also be the symptom of some mental or physical diseases or disorders, such as anorexia nervosa or the cachexia associated with cancer or AIDS.
Dieting is the practice or habit of eating (and drinking) in a regulated fashion, usually with the aim of losing weight. It is also used in some cases to gain weight or to regulate the amounts of certain nutrients entering the body.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.
Successful weight loss diet is all about energy in versus energy out. If a person takes in less food energy 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 (37,600 kJ per kilogram of fat); therefore, if a person creates a deficit of 500 calories per day, the person will lose approximately 1 pound of fat per week (5,400 kJ per day to lose a kilogram a 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/kg) per day is sufficient.)