Is it just your eating that has suffered or do you neglect yourself in other ways? In my experience, if you are wearing clean clothes, have showered recently and aren't showing other signs of self-neglect then your psychiatrist will not be overly worried about your weight, especially if you are aware of the need to eat. They may prescribe food supplements that are high in nutrition but easy to eat if they think it would help.

Hospital is very much a last resort and there aren't enough beds so it is unlikely you would end up on a ward unless there was a really serious safety concern, e.g. you were thinking about suicide within the next 24 hours.