Try using Carnation Very High Calorie. It has 560 calories per can. It can be purchased thru the Amazon link right here on the forum. Its a bit think so I dilute it with adding extra water. Thats just my personal preference.

My oncologist told me that I should not lose any weight while going thru treatments. I could have lost several pounds without a problem. But he insisted that the goal was to not lose any weight. I ended up losing 65 pounds and being hospitalized for malnutrition and dehydration a couple times.

A 17 pound weight loss in 3 weeks is way too much! His diet should be a minimum of 2500 calories daily. If he is getting 2500 calories daily and losing weight like that then he needs to up his calories. Its ok to get 3000 or even 3500 calories daily while going thru treatments. During that time his body burns up calories very quickly. Without proper nutrition he will begin to feel run down. Pay very close attention to his calories and also water intake daily. This can mean the difference between feeling horrible and getting hospitalized or getting thru this easier.