What does your vet say his ideal weight should be? What is his current weight? Are there any other medical issues (pancreatitis, ckd, ibs, etc.)? Has an ultra sound been done to ensure everything is ok in the abdomen?
What has worked for me:
Warming the food
Offering different foods
Bonita Flakes (if you have an Asian market you may be able to find them there, if not
Amazon has them but you would have to wait) - add to existing/regular food.
Tuna water/Tuna added to food.
Change the food bowl to a flat plate
I know
@carfurby (Carla) has the list handy on feeding tips. Tagging her to see if she can post it.
I don't have any experience on these foods (they are prescription from the vet) but they are what was recommended for force feeding - they are higher in calories. I used watered down, mushed Turkey & Giblets FF.
Royal Canin Recovery RS 7% carb
Iams Maxcal 9% carb
Are you equipped to force feed? I got these from my vet (trust me I could not find them anywhere locally). If you don't have these see if you can get them from your vet:
https://smile.amazon.com/dp/B010BWOOXA/?tag=felinediabetesfdmb-20
I used the lower half of the hard sided carrier (took the top off) and put a towel in the bottom. This "contained" Gizmo is a small area with sides. Keep a warm wash cloth handy to wipe the excess (and there will be) and go slow. The slower the better.
Another option would be a feeding tube.