
I would think that 200g would be way to much, especially for weight loss. My Elkhounds at 20 inches tal are the same weight as this overweight cocker, and they eat 200g, and have a good deal of excersise.
I would think that this cocker needs to loose in the region of 10-15 poounds in weight.
When I have had to dietr mine, they have been fed between 100 and 150g of a maintenance diet.
With this being a smaller breed I would expect 150g would be a maintenance amount, so 100g would get the weight off steadily.
Some people will add low calorie vegetables to make up some bulk so that the dog feels full. Carrot and unsweetenmed Pumkin (in USA) sem to be favourites, as well as green beans, Cabbage etc.