Pregnancy

This is the most obvious cause of weight gain and a potbelly. Although it may seem obvious, some pet owners are completely unaware that their cat or dog is pregnant until a small army of fur babies stares them in the face.

Ascites

A common side effect of heart disease is a condition called ascites, which is an accumulation of water in the abdomen. The outward symptom is a swollen abdomen, which is not the same as eating too much or not exercising enough. Tumors or diseases of internal organs cause the body to react in this way. In very young animals, fluid abnormalities in the abdomen may be the result of a congenital defect that causes abnormal blood flow to the heart. Another cause of ascites may be related to a portosystemic shunt, also called a hepatic shunt, in which the circulatory system bypasses (shunts) the liver. Feline infectious peritonitis (FIP) is one of the leading causes of ascites in cats.

Prescription drugs

Some prescription drugs can also cause weight gain if taken long-term. If your pet is taking any kind of medication and also has a weight problem that cannot be controlled by simple food management and moderate exercise, you will need to consult with your veterinarian to see if the medication is related to the weight.

Parasite

Internal parasites, especially the types that live in the abdominal wall and intestines, often cause fluid to accumulate around the infected area, causing a pot-bellied appearance. This phenomenon often occurs in young animals when the immune system is not yet strong enough to resist the effects of parasitic infection, and is even more severe when the internal parasite load is heavy.

Hypothyroidism

The thyroid gland is responsible for producing thyroid hormone. It is the primary driver of energy used by the body. Energy is taken into the body in the form of food. Under normal health conditions, the body burns this energy during normal activities. However, the production of thyroid hormones can lead to a slow metabolism and excessive energy retention in the body, resulting in weight burden. This condition is called "hypothyroidism." Even if your pet eats very little, she continues to gain weight. This is because even the small amounts of food energy she takes are stored rather than released through metabolic processes. Some other symptoms of this disease are fatigue, rough hair, slow heart rate, itchy skin, and dry skin.

Cushing's disease (hyperadrenocorticism)

In older animals, especially older dogs, Cushing's disease is a disease caused by long-term excess secretion of glucocorticoids, a protein , an important aspect of carbohydrate and metabolic regulation. This hormone is associated with the adrenal glands (found near the kidneys) and the pituitary gland, and occurs when something in these glands becomes abnormal. In the case of adrenal cortisol, this condition is caused by cortisol (a type ofCaused by overproduction of steroid hormones). Cushing's disease is often characterized by muscle weakness and weight loss, extreme thirst, increased appetite, urinary tract infections, rapid weight gain, and hair loss. One of the most obvious outward symptoms is a big belly. If you suspect your pet has Cushing's disease, you will need to take your pet to the veterinarian for a full blood, urine, and chemical analysis.

Bloat

Some dogs will eat their food quickly due to their origins, current living conditions, health or personal characteristics. This behavior is called "gobbling" by some pet owners and is often described as if the dog devours its food without tasting or chewing it - or "devouring" it. When a dog "swallows" its food, it is also swallowing a large amount of air. Undigested food and excess air in the stomach, causing a condition called gastric dilatation and volvulus syndrome (GDV), more commonly known as bloat. In addition to the obvious distended abdomen, dogs with distension often experience symptoms of difficulty breathing, rapid heartbeat, abdominal pain (to the touch), drooling, and collapse. This is a life-threatening condition that requires immediate medical attention. Bloat is most common in large dogs such as Great Danes, German Shepherds and Standard Poodles.