Take a look at your dog's kibble or diet! You want the first ingredient to be meat (like chicken, beef, venison, etc) and one of the next few after that to be an organ meat (like chicken liver) or a meat meal or by-product (which sounds unhealthy, but the organ meats and other animal parts used to make meat meal contain important vitamins and minerals). Eggs are fantastic too. If your dog's kibble doesn't already include eggs, giving your dog an egg per week can supplement their protein intake and be a good source of the essential amino acids dogs need but can't make within their bodies. The egg shell is a great source of calcium, but I wouldn't give them the shell without drying it out (by baking it in the oven on a low temperature, for example) and then grinding it up to a consistency like salt or flour.
A lot of kibbles will have large amounts of corn, rice, or wheat (or by-products or meals of them) as a filler ingredient- those are carbs and give a lot of energy with little nutrition. It's important for your dog to have a certain amount of carbs, but you generally don't want to see grains and other primarily carbohydrate foods in the first three ingredients or so. At least two of the first three ingredients should be forms of protein.
For dogs who don't have allergies, digestive dysfunction, or other special dietary requirements, the most easily digestible proteins tend to be eggs, chicken, and organ meats like liver, heart, or gizzard. Organ meats are perhaps the most healthy when considering the vitamins your protein supplies, but they also contain more phosphorus than calcium, meaning that if your dog receives organ meat aside from their kibble on a regular basis, you'll need to talk to your vet about a calcium supplement. (Eggshells can be used as a calcium supplement, but it can be hard to get the balance right.)
If your dog's kibble is primarily grain and you aren't in a place to switch kibbles, consider supplementing the dog's diet instead. You can look into raw or home-made diet plans and forums for advice on what kind of things to give. (Note that giving raw meat to a dog who's never had it before may cause stomach upset until they get used to it.)
The dog's diet overall (including kibble, supplements, home-made, and human food) should be around 40% protein. This can vary between 30 and 50 percent, but note that high protein diets (especially when applied to large breed puppies) can cause overgrowth and, by extension, many other health issues. Research thoroughly and consult your vet before going over 40%.
Carbohydrates like corn and rice should be 15-25% of the diet, as they give your dog short term energy. Think of a diabetic human experiencing a drop in blood sugar; they might eat a cupcake ... (more)
You can give him less food or healthier food and exercise more.
I have had very helpful people at the pet stores steer me to the more healthy dog food. No matter what kind of problem you might have with your pet, the food can be the answer. It would be worth a try.