First question is whether he has been to see a vet recently to rule out the cause being a physical issue?
If a physical issue is ruled out if you look through the BARF/RAW section of the forum there is a wealth of information regarding balanced homemade diets if that's what you're interested in. Can you lay out his meals in more detail?
Jasmine - Female Miniature Poodle - born Aug 15, 2010
Loker Delgado Von Stalworth - Male GSD - born Jan 26, 2012
Koda & Zazu - 5 year old male cats
Alex - Male Cocker Spaniel (rescue) - RIP Cuddlebug 2007-2010