His recovery can take every bit of 2 years from the date he finished all treatments and everyone's first year is obviously the worst. He needs to understand this and be patient. I didn't even get back to tasting most foods until my 15th month post Tx. Tell him to get at least 2500 cals a day anyway he can. Forget about the notion of unhealthy foods. If he finds he can eat it, then do so. I always drank a can of Carnation Instant Breakfast VHC with every meal just to make sure I at least was getting 560 nutritionally balanced cals. I ended up with a sweet taste post Tx so it was not uncommon for me to eat pancakes and sunny side eggs smothered in syrup for lunch or dinner. I also found those TV dinners usually had sauces and gravys and high fatty caloric content that were easy to eat. Same for ham steak with mashed potatoes and green peas. Stay clear of white chicken and anything else that doesn't have a high moisture content after cooking.

Believe me I'm not a nutritionist but this worked for me and before long, relatively speaking, he will be eating almost normal again.