There are four main reasons why dogs become obese. One is overnutrition. Overnutrition is the main cause of dog obesity. While ensuring adequate nutrition for dogs, we must also prevent overnutrition. The other is lack of exercise. Not exercising for a long time will cause obesity; the third reason is age and breed. The older the dog is, the more likely it is to be obese, and the breed of some dogs also determines the chance of obesity; the fourth is endocrine disorders. If the dog has been neutered Surgery or other surgeries will more or less cause endocrine disorders in dogs, making dogs prone to obesity.