Hattie,
I’ve always had Labs and mine have all been “easy keepers”, meaning that they had low energy requirements. If your Lab is an “easy keeper” then for weight loss you’ll be decreasing calories down to a point at which you need to watch nutrient levels to ensure that all nutrient needs are being met on fewer calories.
You have a good start by measuring her food. Did you measure her food before starting her on a weight loss program? If you did, the best way to know how many calories to feed for weight loss is to cut back about 15-20% from the number of calories she was consuming. A reasonable weight loss goal would be 1-2% a week. If she isn’t loosing then you need to decrease calories/ increase exercise or both and then weigh her the next week and adjust as needed to reach a 1-2% /week weight loss.
In regards to protein. an easy rule of thumb is 1 grams for each lb ideal body weight. So if her ideal is 70 lbs that means 70 grams protein a day. Currently with the 3 cups Fromm and .5 cup Keen you are feeding about 78 grams a day. If you decrease the calories to 1000 calories, ~25% decrease, the protein intake drops to ~ 60 grams. She’ll still be meeting NRC recommended amount at that level but you might want to switch to a food geared for weight loss that has a higher percentage of calories coming from protein.
Another rule of thumb is if you are feeding less than 80 % of the manufacturer recommended amount than you need to change foods.
This article is very comprehensive in regards to weight loss https://www.aaha.org/public_documents/professional/guidelines/weight_management_guidelines.pdf
