Definitely DON'T follow the guidelines on the bag. I follow way under for my healthy weight 16lb dog, so for a dog trying to lose, it's going to be significantly less.
For reference, Jackson is at a good weight at around 15-16lbs. He's VERY active and eats on average 2/3 cup per day of a 430 kcal/cup food, I will up it to 3/4 cup per day if he seems hungry or was more active (i.e. he swims all summer, so he usually gets more). But most bags suggest 1 cup - 1 1/4 cup per day for him, and he would be so fat if he were eating that much.
What food are you feeding and how much are you feeding? You want to feed an amount for your dogs supposed-to-be weight, not the current weight they are. So feed for a 7lb dog (but not going by the bag guidelines).
You say you're feeding Blue Buffalo Wilderness... do you mean the Healthy Weight formula? If so, I would not feed more than 1/2 cup per day if it were me. Also, you can use green beans as a filler-upper. Zero calories by the time they're not chewing them
