Our Yorkie Jack is roughly 9.5lbs and is 3 years old. We are trying to determine why he is seeming overweight and our vet says he is. He suffers from chronic pancreatitis and is on Hills ID LowFat dog food. The bag recommends we give him a full cup per day but the vet recommended we go down to 3/4 cup per day. Even with that, he was packing on weight fast. So we dropped him down to 1/2 cup, which we do 1/4 in the morning and 1/4 in the evening. Other thing is he literally devours his food. I'm talking like everything gone in less than 15 seconds. Anyone experience something similar? Idk if we should go on an even lower fat food but I also don't want to starve him. He also gets a good amount of exercise throughout the day with our other Yorkie and we all take 2 mile walks daily.
Any thoughts appreciated

thank you!