How to gain Weight and nutriants after a long term illness?

I need some help, tips. Iv had a long term illness which has made me drop a lot of weight I'm 6ft and now only 55-60kgs. I just don't like eating anymore, are protein shakes any good or any specific superfood any good?

Iv seen a few doctors and they all say have little meals which iv started to but it doesn't really help I'm a smoker as well which does not help.

I have little to no fruit and veg either.

Any advice or suggestions please.
How to gain Weight and nutriants after a long term illness?
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