I feel very guilty saying this... a few years back when the vet said Simba needs to go on a hypoallergenic diet I started feeding him Hill's z/d. The 33% stuff. He was eating that mixed with the cans I have for MC for a year and a half. With z/d kibble as well, so he gained almost 2kg!
In September 2020 he got a cortisone shot to treat his occasional asthma attacks and was put on a diet, where we cut the amount of food offered back by 25%. Then fast forward a few months later when I suspected he had diabetes he had lost 1.5kg. The vet still encouraged to keep his current diet for his "allergies".
Just before Christmas the vet said he could try Royal Canin Diabetic wet food. Then it was still a mix of z/d and RC to make the transition easier, plus Hill's m/d kibble. And after joining the FDMB kibble is out of his life and I have a pantry full of LC.