I think I'd start out with a visit to the vet. Your boy may have an underlying medical problem, like hyperthyroid or even kidney disease.Gizmo may have been losing weight all along, but the vomiting just brought that fact out. Then you also will have the opportunity to talk to the vet about what to feed Gizmo. Gizmo is an older fellow, and that is usually the time these problems show up. Good luck and please let us know how things turn out...