Lean dogs have longer lives
Median life span was significantly longer for dogs in which food was restricted. 
Lean dogs have healthier lives
“diet restriction also was associated with a longer median time to first treatment of osteoarthritis (the most common chronic disease among dogs in this study) and a longer median time to first treatment of any chronic condition.” 
Overweight dogs and cats have an increased risk for urinary stone formations. 
The problem with dry dog and cat foods are the high carbohydrates. Many veterinarians and nutritionist recommend if your dog or cat is overweight cut the carbs!
"Calorie restriction—but not protein restriction should be pursued in overweight animals to achieve a slow rate of weight loss of 0.5% to 1% weekly." ... "Diets high in protein appear superior to those with moderate amounts of protein"
Using the gold standard pet food formulator Steve Brown recommends carbohydrates would be 6% of calories. (Dry kibble ranges from 20% to 60%+) The ideal remaining calorie breakdown would be 49% of the calories would come from protein, and 44% from fat. Remember that the percentage of calories is not the same as the "guaranteed analysis" %. We will show you how to determine the percentage of calories later with the Pet Food Math Cheat Sheet.
“Limiting dietary carbohydrate is an important component of metabolic control for weight loss. There are three key advantages to limiting dietary carbohydrate to 20% (DM) or less: 1) lower glycemic index, 2) metabolic shift from energy storage to energy usage and 3) increased satiety.” 
One challenge when searching for dog food for a dog with a moderate activity level is finding one that has a percentage of fat that is no more than 50% of the protein listed. Higher fat diets are a great energy source for active dogs but most dogs will get more calories than they can burn on a high fat diet. For dogs that are overweight I would avoid foods marketed for the “less active” dogs. If you checked the label you may find that this food has the same calories or more than the food you are feeding now. Many of these foods contain a high fiber content which can reduce the overall digestibility and insoluble fiber like cellulose can reduce mineral adsorption. High fiber can lead to increased need to defecate and a larger volume of feces. Instead I would limit treats and slightly reduce the amount of food feed, and increase their daily exercise. There’s an old saying, if your dog is fat you’re not getting enough exercise!
“Median life span was significantly longer for dogs in which food was restricted. The onset of clinical signs of chronic disease generally was delayed for food-restricted dogs.”