all those specific foods labeled "low cal", "diet", "lite", "less active", "senior" etc. will hurt more than they will help. they generally have drastically reduced protein and fat content but are full of carbs and fillers. they are not healthy and really only faciliate weight loss in the short term, often at the expense of a good health and coat.
protein, first and foremost, is what a dog needs in his diet. not only is it used to maintain and renew the body, but it also plays a large role in many different metabolic functions. dogs also utilize it as a source of energy. it's what they evolved eating, over thousands of years.
fat is also important for the body (especially skin and coat health), and is a major energy source for dogs. in addition to that, various fatty acids are also required by the body for specific functions.
you've heard of both essential amino acids (from protein) and essential fatty acids (from fats and oils), required in very specific amounts for the body to function - but there are no sources that make mention of any sort of "essential carbohydrate", and for good reason: dogs don't need them in their diet, and not even the biased research sponsored by pet food companies has been able to confirm such a thing.
the best way to help a dog lose weight is to decrease overall caloric intake (i'll get back to that in a moment), and to increase exercise if at all posible. just be careful to not overdo it in the beginning, since just like with overweight people, overweight dogs put more stress on their joints and can get injured more easily than animals at their ideal weight.
back to reducing caloric intake. the first rule is that you want to feed your dog the amount of food required to meet his needs at his ideal/target weight. don't laugh, but many people think along the lines of "my dog weighs X pounds and the bag says to feed Y cups at his weight but he's still fat" when they should be basing the daily feeding amount on what the dog would weigh at a normal, healthy weight. i really don't want to step on any reader's toes, but this is a very common mistake i encounter with many people i've consulted on nutrition and now it's one of the things i always bring up.
the next thing is the distribution of calories in the food formulation. both protein and carbs supply 4 kcal per gram, while fat supplies 9. since almost all foods that contain a high amount of protein also contain a high amount of fat, they are automatically pretty calorie dense, but replacing protein with carbs (which is done in all these "lite" type foods) isn't going to make any difference at all in calorie content - for that you have to cut down on fat as well. protein and fat are the more expensive ingredients in dog food, while carbs (read: mostly grains) are cheap and increase the profit margin on every single bag sold, since lite food generally costs the same and sometimes even more than the regular adult food.
the ideal weight loss food would be a formula that provides a decent protein content (24% and higher, the more the better), enough fat to keep the dog's body, skin and coat healthy (preferably with a high content of the essential omega 3 fatty acids EPA and DHA, but some saturated fats are important too) but not too much, in order to cut down on calories, and a decent source of fiber to make the dog feel full longer, without creating spikes and drops in blood sugar levels, which is stress on the body and makes people and pets feel cranky and miserable.
sadly there aren't many foods that fit these criteria, because it's a costly recipe and most large food manufacturers aren't interested in the relatively small profit margin.
so generally the best recipe is to feed the proper amount of a good quality adult food, and if the amount is too small for the dog to feel satisfied, bulk it up with healthy veggies like green beans, squash, zucchini and so on. if you cook them in a bit of garlic water or low-sodium chicken broth, most dogs love the taste.
another option is to find a good quality "lite" food and replacing about 1/3 of the recommended feeding amount with lean meat (cooked or raw) and a good quality fish oil supplement. this cuts down on caloric intake but still supplies good quality protein and fat.
...any advice is appreciated
