A patient on megastrol acetate may experience:

Megestrol acetate is a synthetic derivative of the hormone progesterone that is commonly used as an appetite stimulant, particularly in patients diagnosed with conditions like cancer or HIV/AIDS, where cachexia (weight loss and muscle wasting) is a concern. One of the primary effects of megestrol acetate is to increase appetite, which can lead to weight gain in patients who have been experiencing significant weight loss or who might be anorexic.

This appetite stimulation is particularly beneficial for patients who have difficulties maintaining weight or who have lost weight due to illness or treatment effects. Therefore, it is expected that a patient taking megestrol acetate would experience an increased appetite as a key therapeutic effect of the medication.

The other options do not accurately reflect the primary intended effects of megestrol acetate. Generally, the objective of prescribing this medication is to combat decreased appetite, weight loss, and nausea, which are more common symptoms in patients requiring this treatment. Hence, the correct choice emphasizes the drug's core purpose of boosting appetite, supporting the overall aim of improving nutritional intake and quality of life for vulnerable patients.