Sensible diets or weight management plans are designed to be used for a lifetime, says the American Heart Association. Fad diets, however, often give you the idea that you only need to follow them for a certain number of weeks or months. Fad diets also usually neglect to include exercise as part of their weight-loss plan. Regular exercise can help maintain weight loss gained through dieting. These diets also tend to emphasize dubious claims such as "fat-burning foods" or food combinations that cause you to lose weight. Talk to your health care provider about a healthy and sensible eating plan.