Top 5 Indications for Appetite Stimulation

Regulation of appetite and food intake is a complex process orchestrated by specific centers in the hypothalamus and impacted by various hormones, neurotransmitters, and visceral inputs. Numerous conditions can cause hyporexia (ie, a decrease in food intake), which can cause challenges; timely intervention with an appropriate appetite stimulant may improve voluntary food intake and support successful patient outcomes.

Following are 5 common indications for appetite stimulation according to the author.

1. Acute Illness Causing Hyporexia

Several acute illnesses can impact appetite, and evidence suggests that many hospitalized dogs and cats fail to voluntarily meet nutritional requirements.^1,2 Previously well-nourished patients may tolerate short (ie, <48 hours) periods of anorexia, but persistently poor intake can impact numerous physiologic processes (eg, enterocyte turnover, GI permeability, systemic immune response) in various species.³  

Human studies have shown that inadequate nutritional intake typically results in longer hospital stays and increased mortality^4,5; this is typically less recognized in companion animals, although data indicate an association between inadequate food intake and poor patient outcomes.^1,2 Unless oral intake is directly contraindicated, patients should typically be encouraged to eat as soon as problems such as frequent regurgitation, gastric stasis, or intestinal ileus are effectively managed.⁶ Infrequent vomiting, diarrhea, and conditions such as pancreatitis should not be regarded as reasons to withhold food, as oral intake of even small amounts of food can protect GI tract health and function.⁷ Suboptimal intake should not be considered acceptable, as patients recovering from acute illness are often in a hypermetabolic state and need substantially more calories and protein than usual.⁴ An appetite stimulant should be introduced promptly in patients recovering from acute illness to support adequate intake of an appropriate diet.

2. Chronic Illness

Many chronic disorders (eg, renal disease, cardiovascular disease, cancer) are associated with progressive weight loss.^8-11 Affected patients may become cachexic, a state in which voluntary intake is poor and the body’s muscle proteins—rather than fat stores—are used to supply energy. The underlying disease process can increase metabolic rate, and weight loss can occur more rapidly than with simple starvation. 

The impacts of unaddressed protein–energy malnutrition have been well established in human medicine, and intervention in affected humans may improve quality of life and longevity.^12,13 Studies in companion animals with chronic kidney disease or heart failure have shown associations between BCS and longevity, and nutritional intervention may improve the well-being and outcome of these patients.^8,9,11 If weight loss regardless of appetite is noted when a patient is diagnosed with a chronic disorder, an appetite stimulant should be included as part of the initial treatment plan. The stimulant can be adjusted or discontinued as appropriate and may prevent further decline in physical status. 

In addition to the expected physiologic benefits of an improved energy balance, enhanced intake will likely reassure owners of their pet’s overall comfort and quality of life. Similarly, a consistent appetite supports compliance with complex medication plans; owners may become disheartened and frustrated by the effort needed to administer oral medications to a hyporexic pet. A full dietary history, including weight, BCS, and muscle condition score, should be obtained routinely in dogs and cats with chronic illness¹⁴ and an appetite stimulant prescribed as soon as concerns regarding intake are identified.

3. Transition to a Veterinary Therapeutic Diet

Specific nutrition is routinely recommended for the management of various conditions (eg, urinary tract disease, chronic enteropathy, atopic dermatitis, liver disease, chronic kidney disease, diabetes mellitus, pancreatitis).¹⁵ Diets often play a key role in successful patient management, but patients may be reluctant to eat an unfamiliar food. 

Owner compliance with a new diet can be problematic if the pet seems reluctant to eat; owners may be tempted to add treats or continue to mix in the old food under these circumstances. Administration of an appetite stimulant prior to introduction of a new food may support adequate intake during the transition and encourage owner compliance with feeding a therapeutic diet. The appetite stimulant can be gradually withdrawn after a few weeks while the patient’s intake is carefully monitored.

4. Postoperative Care After Elective Procedures

Elective soft tissue or orthopedic procedures can result in short periods of postoperative hyporexia. Although the prevalence of postoperative anorexia in companion animals undergoing routine surgery has not been well studied, one study reported that only 7 out of 15 juvenile beagles given buprenorphine prior to routine ovariohysterectomy consumed food within 26 hours of extubation.¹⁶ There can be numerous reasons for poor postoperative intake, including discomfort, alterations in GI motility associated with anesthesia, anxiety related to hospitalization, and medications prescribed to manage pain or prevent perioperative infection. 

Because poor food intake is often a major concern for owners, preemptive strategies to promote adequate intake in postoperative patients can be helpful. An appetite stimulant should be incorporated into the in-clinic postoperative care plan for patients undergoing elective surgical procedures and continued briefly following discharge.

5. Boarding & Environmental Changes

Changes in environment can cause a range of clinical and behavioral signs, including decreased food intake in both dogs and cats.^17,18 This is a particular concern in obese cats, as serum chemistry and histopathologic changes associated with hepatic lipidosis may be noted after only 2 weeks of fasting.¹⁹ Although dogs adapt better than cats to starvation, immune responses and GI function are impacted in both species by relatively short periods of anorexia.²⁰ 

Consistent intake encouraged by giving an appetite stimulant may also reduce the likelihood of diarrhea and other clinical concerns in boarding animals. In addition, owners of boarded animals are often worried when food intake is down and may be reluctant to board their pet in the future. Prescribing an appetite stimulant at the start of the boarding period may prevent stress-related hyporexia and weight loss and provide reassurance to anxious owners. 

Although this issue has not been specifically investigated, animals with chronic illnesses may be particularly vulnerable to poor intake when housed in a new environment, and preemptive use of an appetite stimulant may be especially beneficial.

Conclusion

Numerous conditions and situations can cause poor food intake, and clinicians should be attentive to changes in patient body weight and other evidence of decreased appetite. Food intake, including type and amount, should be discussed at every visit and assessed daily in hospitalized patients. Early intervention is ideal, and clinicians should consider an appetite stimulant in hyporexic patients and those vulnerable to inadequate intake.