Serious Replies ONLY...Weight Issue With Sm. Dog ?

7 yr. old MinPin.(spayed) Gets 2 "power walks", each day, for 30 mins., 5 -6 days per wk. Dry dog food: Chicken soup for... Does NOT have a thyroid issue. (blood work performed). However, vet is not really a "nutrionist". (They want to sell you the brand of foods, that they market for companys.) She is maintaining a weight of 12 lbs. (HUGE!) Question: What type of food for small, indoor, over-weight dogs?? Thanks so much, guys!