Final answer:
Weight loss is the indication to increase nutritional intake for a client with HIV, as it can signify wasting and further immune system compromise.
Step-by-step explanation:
The student's question pertains to the identification of a symptom that would indicate the necessity to increase a client's nutritional intake who has been diagnosed with HIV. Among the options provided, weight loss is the correct answer. This is because weight loss can be indicative of the syndrome known as wasting, which is common in the advanced stages of HIV and can lead to further compromise of the immune system. Increased CD4 cell count and stable BMI are generally positive signs, while an elevated viral load indicates a high level of viral replication but is not directly related to nutritional intake.