The term
dieting most often refers to the revision of food intake in order to lose weight. Diets are also observed for a
wide range of medical reasons or to accord with dietary laws, or health and ethical positions such as vegetarianism. In the United States and other developed nations where obesity is a common metabolic problem, the promotion of weight-loss programs has become a large enterprise. This interest in
dieting is caused in part by a cultural emphasis on slimness, but obesity is a genuine medical hazard that puts people at risk for cardiovascular diseases, diabetes, and other disorders.
People often find diets hard to maintain, in part because they may have unrealistic expectations about how quickly they can lose weight. They may blame the diet itself and try another one. Many fad diets are unhealthy and even dangerous if followed for any length of time. Proper weight-loss diets observe good nutritional practices and balanced food intake, including the recommended daily regimens of vitamins and minerals, and exercise.
General Guidelines
In nutritional science, food energy is spoken of in terms of a heat unit, the calorie (actually the kilocalorie). The only sources of
calories are carbohydrates, proteins, fats, and alcohol. If the number of calories taken in greatly exceeds the number used, the excess is stored as fat and obesity results. With proper dieting and exercise the fat stores in the body will supply some of the dieter's energy needs while maintaining good health. For most people, the recommended rate of weight loss is about 0.7 to 0.9 kg (1.5 to 2 lb) per week. This can be achieved on diets limited to 1,200-1,500 calories a day for women and 1,800-2,000 calories a day for men; calorie needs of children vary greatly, and their rates of weight loss should be prescribed by a physician or registered dietician.
The most sensible approach to weight loss is to begin with a medical checkup to make certain that no special health problems exist and to get a diet and exercise prescription from a physician or registered dietician. The diets that are acceptable to the medical establishment are those in which fewer calories are eaten and exercise is increased. This is called the calorie-balance approach to dieting. Although some diets may place more emphasis on calorie reduction and others on increased exercise, all of them emphasize good nutrition and maintaining a balance of proteins, carbohydrates, and fats.
Diet Problems
There are a number of problems associated with dieting. Research has shown that in many cases, diets are successful only on a temporary basisÑmost dieters regain the weight, plus more, within two years. Many of these dieters try to lose the weight again, a cycle called yo-yo dieting. Some studies have found that yo-yo dieting can alter a person's metabolism, making the weight easier to regain and harder to lose each time. Yo-yo dieting has also been linked to heart diseases and an increased death rate.
Another problem is that many of the commercially offered diets emphasize one dietary element at the expense of others; such practices present health problems. Low-carbohydrate diets, for example, restrict the amount of bread, sugar, and grains while maintaining a normal amount of protein and fats. Most of the initially rapid weight loss from such programs is from the body ridding itself of water and salt. A plateau is reached after one or two weeks, and no additional weight is lost for several weeks thereafter. Most people experience fatigue, hypotension (low blood pressure), and dizziness after only a few days on such diets.
High-protein diets virtually eliminate carbohydrates and fats. Because carbohydrates are the most readily available source of energy, an all-protein diet forces the body to burn stored fat and protein. When these stores are metabolized, a condition called ketosis results. This is a serious complication of both diabetes mellitus and starvation and can lead to comHigh-protein diets can be used for only a short period of time and are dangerous for anyone with diabetes, kidney disease disorders, or other medical problems.
High-fat diets, requiring complete elimination of carbohydrates for the first weeks with very small amounts added during successive weeks, also cause ketosis. Diets high in fats and cholesterol are hazardous for persons with atherosclerosis and heart disease. This type of diet also causes diarrhea, vitamin loss, hypotension, dehydration, and kidney irritation.
Numerous diets emphasize one food, such as rice, grapefruit, ice cream, or yogurt. These are not nutritionally balanced and require vitamin and mineral supplements. Formula diets in liquid or powder form, which typically supply from 900 to 1,200 calories per day, claim to contain the recommended daily allowances of nutrients; serious health problems have sometimes been reported with their use. Nonprescription drugs called anorexics are supposed to suppress the appetite but have little effect by themselves and must be used with a sensible diet plan; they, too, may be harmful. As for starvation dieting, this dangerous practice should be attemptedÑif at allÑonly under strict medical supervision. Such extreme practices may also indicate psychological disturbances such as anorexia nervosa and bulimia.
Group Approach
One successful weight-loss technique is the group-support approach of Overeaters Anonymous, patterned after Alcoholics Anonymous. Commercial programs such as Weight Watchers and Jenny Craig have been successful with a nutritionally balanced, low-calorie diet; both provide prepared food to help the dieter with portion control.