To lose weight, people must eat less, exercise more, or do both. Although hundreds of "miracle" products and "revolutionary" diets have been marketed, no pill, potion, or dietary plan can produce weight loss without exercise or lowering of caloric intake. To lose 1 pound or fat it is necessary to burn 3500 more calories than are taken in. Professional help may be required to clarify and modify the behavior that contributes to overeating.
The most sensible weight-loss methods aim for a steady reduction of about 1 pound a week. The diet that experts recommend most often is a balanced, low-calorie, low-fat food plan that is easily adapted for long-term maintenance. Although unbalanced diets can cause weight loss, they are usually too monotonous for long-term use and are followed by weight gain when the user returns to "normal" eating. Repeated dieting followed by weight gain ("yo-yo dieting") may increase the risk of premature death from heart disease and several other diseases, but the research on this is not conclusive. For most people, the most important factor in successful weight control is exercise.
Many people diet even though they are not overweight. The majority of people concerned about their weight would probably do better to focus on exercise, healthful eating, and minimizing cardiovascular risk factors rather than on counting calories.