One of the most devastating and potentially serious diseases to affect our dogs is that of obesity. Thankfully, it's also one of the most easily prevented and treatable diseases. Usually the result of neglect or misinformation, oftentimes all it takes to reverse the adverse affects of obesity is education and a willingness to help your dog improve his or her quality of life.
Obesity is a condition in which your dog's percentage of body fat is significantly higher than it should be, resulting in their carrying around a lot of extra weight. This extra weight affects the entirety of your dog's health. It places them at a much greater risk during any surgeries that might be necessary for other diseases; weakens their joints and cartilage, leaving them prone to injuries; and creates an incredible amount of stress on organs and bones that are surrounded by thick walls of fat. Perhaps the most problematic issue is that the heart simply has to work that much harder to pump blood to all parts of an obese dog's body, and as such congestive heart failure is that much more likely.
Obesity usually becomes a problem when an owner doesn't know what a properly fed dog looks like and mistakes a perfectly fine animal for a malnourished one. With most any dog, you should be able to easily feel his or her ribs by placing your thumbs along their spine and feeling down their sides. Any thick deposits of fat that prevent the ribs from being felt are sure signs of a problem. In addition, when viewing the animal from the side, there should be a very obvious delineation of the animal's waist. At the point just behind the ribs, there should be a somewhat dramatic and obvious "tuck-up" where the abdomen is held tightly up and doesn't sag down to the level of the ribs (or even below it).
The most important step to preventing and curing obesity in your dog is to become educated about canine nutrition. Find out from your vet exactly what amount of food and exercise is required for your breed and then stick to it as closely as you can. If you're one of those owners who has historically used food as a substitute for attention, this is something you'll have to stop as soon as possible. A dog that is used to being rewarded with food may find the situation dire if it's brought to a sudden stop, but you must nevertheless ignore his or her pleas, remaining confident that once your dog's caloric needs have been met, he or she is not "suffering", but simply practicing manipulative behavior.
Generally, a change in diet itself isn't necessary, just controlling the amounts that your dog is allowed to eat. If he or she still seems unsatisfied after a few weeks of eating the new restricted amounts, you can add bulk to their meal by introducing a few low-calorie vegetables such as carrots or greens, so long as these agree with your dog's digestive system. In addition, taking your dog out for prolonged exercise several times a week is critical. Obese dogs will tend to become lazy and as such, they'll depend on you to get them active. Taking them to a park where they can interact with other dogs seems to work best.
In general, just be wary of the amount of calories your dog consumes on a daily basis and how much exercise he or she is getting. The solution might seem overly simple, but that's exactly why obesity is known as the most preventable disease.