sorry i missed your post yesterday. anyway.....i'm sorry to hear that your friend was sick. losing 13lb in a few days is significant for a healthy individual - so i hope there is really nothing wrong other than stomach flu. sport nutrition is rather complicated as different sports require different eating program. i really hope he has a sport nutritionist to work with. anyway, 2 ways to gain weight : 1) increase portion size, and 2) increase caloric density. increasing portion size is more difficult as one can only stuff so much in his stomach

Increasing caloric density is more practical and the easiest way is to work on the drinks. you may find some HiPro HiCal smoothie recipes below to start with. Caution: not to overload on protein.
http://www.bccancer.bc.ca/NR/rdonlyres/45B...uidRecipes1.pdf