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The promise of a quick fix
Fad diets promise—and may even deliver—rapid weight loss, offering a short-term solution to a permanent problem. The tendency to gain weight will not go away after a few weeks of eating only grapefruit or bacon. A diet so unbalanced that you can't stay on it for more than a few weeks or months without feeling awful is of no use for lifelong weight control. And the lack of balance can hurt your health. Extreme high-protein, low-carb diets can lead to vitamin deficiencies, a loss of bone density and other problems.