I do agree about not giving in, my husband lost weight rapidly after pneumonia was treated in hospital.
I was told he would never get it back. I ignored the advice about adding sugar and cream to his diet. I did add a little but only to make things more palatable.
I fortified by using by adding eggs and low fat milk powder to many foods. I could not get ensure on prescription but some gave me some as she no longer needed it. I made blended soups and smoothies. Puddings etc. Mini meals and snacks helped.
So there are ways to feed well. Now on can buy a tasteless organic grass fed bone broth powder. This is high in protein and soothes the gut too.
But as well as not giving in, Life is about letting go too, it is a very fine balance, a very personal one.
Feed up yes, but feed your own inner resources to cope if this fails. We can do our best but only that.
I have got my husband back and fit several times but each episode takes longer. Be patient.