My dog is fat. Help!

as the weather warms up a dog needs less calories to maintain weight...from what I have read in the past the right balance of nutrients are based off of what the food manufacturer has put on the label for feeding instructions...so if it says on the bag to feed 2 cups a day and you are feeding one cup a day it is possible that the dog is not getting all the required nutrients even though it is getting enough calories to maintain weight...you can switch to a lower fat and protein dog food in the summer months...during cold and colder weather the dogs require more calories to maintain weight and quite a bit less during the hot months...I feed the same feed year round and my dog food bill cuts almost in half for a good while...I am sure that the dogs would perform better switching to a lower calorie diet in the hotter months that is properly balanced with calories and nutrients...