Final answer:
The community psychiatric nurse should explore ways to help the patient stop smoking to address the patient's health and social isolation.
Step-by-step explanation:
The best response by the community psychiatric nurse would be to explore ways to help the patient stop smoking. This is important because smoking can worsen the patient's health and contribute to social isolation. The nurse can discuss smoking cessation programs, provide educational materials, and offer support in quitting smoking.
Assessing the patient's weight and determining foods and amounts eaten would be necessary to evaluate the patient's nutritional status and address any deficiencies or imbalances, but this is not the immediate priority in this situation. Hospitalization might be considered if the patient's condition worsens, but it is not the initial response. Reporting the situation to the shelter manager may not directly address the patient's mental health needs.