The risks of fad diets on long-term health include nutritional deficiencies and metabolic imbalances. Many fad diets promote extreme calorie restriction or eliminate entire food groups, which can deprive the body of essential nutrients, vitamins, and minerals. Rapid weight loss associated with these diets can lead to muscle loss and a slowdown in metabolism, making it difficult to maintain weight loss afterward. Additionally, these diets often lead to a cycle of yo-yo dieting, negatively impacting physical and mental health. Sustainable, balanced eating is key to long-term health.