My late husband died 10 years ago of a chronic illness. I was told that I had to keep his weight up (he was ill for eight years before he died.)
I reverted to feeding on demand, when he felt hungry I cooked for him, I gave him high fat foods such as cream cakes, fried breakfasts, fish and chips, ice cream, meat pies and fruit pies with custard or cream. He put on two stone in weight and kept the weight on until the day he died of pneumonia. The matron asked me how I had done it and asked me to speak to student nurses so they could write a paper on my technique. At the beginning he didn't feel like eating much but slowly he ate more and more until he was having full Roast beef dinners, sometimes in the morning as he felt hungry. We used to go out with his mobility scooter and oxygen and call at Subway and get foot long sub sandwiches, then next door to Greggs for cream cakes.