Final answer:
Anorexia nervosa and bulimia nervosa typically decrease the metabolic rate lower than normal, as the body slows down metabolism to conserve energy during periods of starvation in anorexia or binging and purging in bulimia. The correct option is b.
Step-by-step explanation:
Anorexia nervosa and bulimia nervosa commonly affect the patient's metabolic rate by often decreasing it lower than normal due to the body's response to starvation and inadequate nutrient intake. These disorders can drastically alter the way the body processes energy, leading to a slow metabolic rate as the body attempts to conserve energy.
Anorexia nervosa is characterized by severe calorie restriction, which can lead the body to reduce its metabolic rate as a survival mechanism.
Similarly, bulimia nervosa can interfere with normal metabolic rates through cycles of binging and purging. Although patients with bulimia nervosa may appear to maintain a normal weight, their eating behaviors can still result in metabolic dysregulation.
It's important to note that alterations in metabolic rate can contribute to the many health risks associated with these eating disorders, which can include bone loss, heart and kidney failure, and even death. Option b. is the correct one.