After an adolescent diagnosed with attention deficit-hyperactivity disorder (ADHD) begins methylphenidate (Ritalin) therapy, a nurse notes that the adolescent loses 10 pounds in a 2-month period. What is the best explanation for this weight loss?

Side effects of Ritalin cause nausea; therefore, caloric intake is decreased.

Increased ability to concentrate allows the client to focus on activities rather than food.

Hyperactivity seen in ADHD causes increased caloric expenditure.

The pharmacological action of Ritalin causes a decrease in appetite.