MYTH: Fad diets work for permanent weight loss. FACT: Fad diets are not the best way to lose weight and keep it off. Fad diets often promise quick weight loss or tell you to cut certain foods out of your diet. You may lose weight at first on one of these diets. But diets that strictly limit calories or food choices are hard to follow. Most people quickly get tired of them and regain any lost weight. Fad diets may be unhealthy because they may not provide all of the nutrients your body needs. .