Max's House


Changes in body weight result when metabolic utilization and/or nutrient loss exceeds or falls short of energy intake. Documentation should be based on serial body weight measurements or on standard body weight charts. Weight loss refers to a decrease in body weight (>l0 per cent of body weight). Weight gain refers to an increase in body weight (>10 per cent of body weight).


Weight loss can be caused by inadequate food intake, increased energy demand, malassimilation of food, or loss of nutrients, fluids, and electrolytes. Weight loss associated with polyphagia is suggestive of malassimilation, excessive nutrient loss, hypermetabolism, inadequate feeding, or adverse environmental conditions. Weight loss associated with anorexia may indicate infectious, inflammatory, neoplastic, toxic, neurologic, or metabolic abnormalities. Weight loss associated with malnutrition can be identified by a complete and detailed dietary history. A thorough dietary history includes calculation of the animal's caloric needs and careful questioning as to the amount and frequency of feeding. Weight loss associated with gastrointestinal signs indicates caloric intake that is inadequate to meet the energy expenditure of the body.


Weight loss associated with fever can be attributed to (1) infectious, (2) inflammatory, (3) neoplastic, and (4) toxic causes. Depending on the site and extent of involvement, infectious agents may cause weight loss via both fever and anorexia. Weight loss without fever is often caused by metabolic disorders such as renal, hepatic, and cardiac disease, which may affect both appetite (usually decreased) and energy demands (increased). Immune-mediated neuromuscular disorders and degenerative joint disease can cause loss of muscle mass. Weight loss can be caused by the loss of nutrients through the gastrointestinal tract (as in parasitism or protein-losing enteropathy) or secondary to the exudative skin conditions (e.g., burns, pyoderma) or urinary loss of nutrients (such as protein or glucose).


A complete blood count, serum chemistry profile, urinalysis, fecal examination, thoracic and abdominal radiography, and thyroid concentrations should be evaluated as needed. Serologic tests (viral, rickettsial, fungal, dirofilariasis, ANA) may be warranted. Contrast radiology, echocardiography, ultrasonography, gastrointestinal endoscopy, exploratory laparotomy with biopsies, and other diagnostic procedures (nuclear studies, such as liver scans) may be necessary to determine the exact etiology of the weight loss.


Caloric intake that exceeds metabolic demands and nutrient loss results in weight gain and possible obesity.


Weight gain associated with polyphagia can be caused by overeating, boredom, drug therapy, reduced physical activity, and endocrine ' disorders. Weight gain associated with anorexia or normal appetite can be caused by overfeeding, genetic predisposition, or hypometabolism. Decreased activity can contribute to obesity. Labrador retrievers, cocker spaniels, collies, and certain terriers may have a genetic predisposition to weight gain. Endocrine disorders, such as panhypopituitarism, hypogonadism, and hypothyroidism, can result in hypometabolism and weight gain.


Weight gain associated with ascites and/or peripheral edema may be caused by hypoproteinemic states, cardiac disorders, infectious or inflammatory abdominal disorders, hepatic disorders, or posthepatic disorders. Hypertensive patients may exhibit weight gain as a result of sodium and fluid retention. Weight gain associated with an increase in lean body mass may result from increased exercise and caloric intake, endocrine disorders such as insulinoma and acromegaly, and drug therapy (e.g., anabolic steroids).

Weight Gain Associated with Organomegaly. Dogs and cats suffering from hyperadrenocorticism exhibit hepatomegaly. Organomegaly in an otherwise poorly controlled diabetic cat on insulin therapy is strongly suggestive of feline acromegaly.


A complete blood count, serum chemistry profile, and urinalysis should be collected. Endocrine testing may be indicated (TSH stimulation test, ACTH simulation test, insulin:glucose ratios) to refine the diagnosis.

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