Final answer:
The statement that fad diets can be difficult to sustain, may exclude nutritious foods, and are not necessarily low-calorie is true. These diets often promote quick weight loss without attention to balanced nutrition, which is not conducive to long-term health.
Step-by-step explanation:
Fad diets are often difficult to sustain and may exclude nutritious foods. While they promise rapid weight loss, they are usually not low-calorie diets and can lack essential nutrients which can compromise overall health. Using sound nutritional principles such as variety, moderation, and calorie control is crucial to maintain a balanced diet and achieve lasting health benefits.
Furthermore, many fad diets are not sustainable as a lifelong eating plan. Once the dieter stops following the diet, weight regain is typical. The key to developing a healthful diet that garners long-term results is to ensure it includes a wide range of nutrient-dense foods to meet the body's needs. It is also important to account for physical activity to balance food intake and energy expenditure.