If you have been feeding one cup a day and she is 20 lbs and needs to lose weight then you’d have to feed less food. In general, a calculated value can be off by 50% meaning some dogs would only need 1/2 cup. of fresh pet to lose weight. But at these levels the dog may feel hungry and because the food isn’t formulated for weight loss she may not get all the nutrient needs met.
If she isn’t getting treats, table tid bits, or dental chews, to cut 80% of calories you’d be feeding 3.75 ounces of Fresh Pet a day. this may not meet her nutrient needs. To me It looks like you’d need to change foods for a safe weight loss program for her.
