Dogs and cats in America are getting fatter. Roughly 80-85 million pets are considered obese. Not only is it unhealthy for the animal, but the health costs can be enormous. Many low fat and diet foods are fed in such differing amounts that they can actually put weight on the animal. Most pet owners don't understand how much weight can be put on a cat or dog with just that "one snack a day".
Overweight animals are more susceptible to diabetes and heart disease. The other conditions that come with obesity are arthritis and cruciate ligament tears. Overweight animals have more weight to carry around, which weakens their joints, which can lead to huge vet bills.
Some dogs are susceptible to orthopedic problems because of their breed and genetics, but they are more severe in pets that are overweight, which can render them practically immobile.
Arthritis and heart disease have been steadily increasing during the last couple of years. Quality of life becomes so bad that even though the pet seems otherwise healthy, they have to be put to sleep because their quality of life is practically gone.
As much as exercise can help reduce weight on dogs and cats, you have to be careful as too much can cause a dog to tear a ligament or damage a hip.
Dogs were meant to hunt in packs and can go days without eating, but cats don't do to well with starvation. With cats if you severely restrict calories, the body may most likely send stores of fat
As with everything else, if you need to change diet or an exercise regimen, you need to do it gradually. The weight did not get there overnight, and it is not going to come off overnight, as most people probably know from their own diet struggles. Just as people age and need to eat less, so do our animal companions.