Final answer:
Fads in health, specifically fad diets, are diets that become popular quickly but often do not lead to significant, long-term weight loss. They are usually unbalanced and restrict important nutrients.
Step-by-step explanation:
Fads in the context of health usually refer to fad diets. These are diets that become popular quickly, often promising rapid weight loss. However, most fad diets do not lead to significant, long-term weight loss and can be unhealthy because they are unbalanced. They typically restrict or eliminate certain foods and nutrients that are important for a healthy eating plan.