Reasons for dogs suddenly becoming fat:

1. Lack of exercise, eating too much without timely exercise and digestion, resulting in fat accumulation.

2. The dog suddenly becomes fat or is caused by irregular diet, such as overeating, etc.

3. It is also possible that the dog suddenly gained weight due to pregnancy.

4. It is also possible that the dog suddenly becomes fat due to certain diseases, such as ascites and other diseases.

Solutions to dogs suddenly becoming fat:

1. If it is caused by lack of exercise, you can take your dog to exercise appropriately to lose weight.

2. If it is caused by irregular diet, it is recommended to feed the dog at a fixed time and with balanced nutrition.

3. If your dog is suffering from a disease, you should go to the hospital for examination as soon as possible and cooperate with the doctor to treat the disease.