Hi,
My husband is 2 years out of treatment and just started to gain weight over the summer. His doctor said his body was using any and all energy (calories) to heal his body. Now he is back up to his pretreatment weight. He can't eat the breads and chips he used to eat due to dry mouth, but he has a new love of ice cream, and of all things steak, he can't get the starches down but has no problem with protein.
Just let your husband know it will probably take more time but his will gain some back.