Weight loss is a physical condition that results from a negative caloric balance, as when metabolic utilization and excretion of essential nutrients exceed the caloric intake. Weight loss is considered clinically important when it exceeds 10 percent of the normal body weight and is not associated with fluid loss.
Weight loss can result from many different mechanisms that share the common feature of insufficient caloric intake or availability to meet metabolic needs. Causes vary markedly from intentional restriction of calories in order to reduce weight in an obese patient, to weight loss associated with life threatening illness.
Historical information is very important, especially regarding type of diet, duration and environment of storage of diet, the patient's daily activity and, environment, the presence of pregnancy, appetite, signs of gastrointestinal disease (vomiting, diarrhea, regurgitation), or signs of any specific illness.
There are several disorders or situations that need to be considered when evaluating patients for weight loss. These include:
Dietary Causes Insufficient quantity of food – not enough calories
Poor or inadequate quality of food
Decreased palatability (taste) of food
Prolonged storage of food with deterioration of nutrients
This is often seen with many disorders and diseases.
Malabsorptive Disorders (poor intestinal absorption) Inflammatory bowel disease (IBD) is a microscopic accumulation of inflammatory cells into the intestinal wall. The cause is unknown, although it is thought to have an immune basis. Diarrhea and weight loss are commonly seen with the disorder.
Lymphangiectasia is a chronic protein-losing intestinal disorder that arises from congestion and dysfunction of lymph carrying structures in the intestines. It is an uncommon disease in the cat.
Intestinal parasitism is most common in younger animals or animals that are housed in crowded and/or unsanitary conditions. It may involve roundworms, hookworms, coccidiosis.
Chronic infections of the bowel may lead to malabsorption. Examples include fungal infections and bacterial overgrowth.
Infiltrative tumors of the intestine may affect the intake of calories.
Gastrointestinal obstructions can prevent adequate absorption of nutrients and result in nutrient loss from vomiting and diarrhea.
Surgical resection of large segments of bowel can greatly decrease the overall absorptive surface of the intestines.