You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

An increase in food intake is an important observation which should be reported to your veterinarian so that tests can be conducted to identify the underlying cause..

Appetite control is closely regulated by special centres in the brain and, when an animal has eaten enough food, it should stop eating. However, sometimes the control mechanisms breakdown and an animal will eat much more food than usual. This is an important observation and should be investigated to determine the underlying cause. Common causes of an increased appetite (called polyphagia) are :

Usually endocrine (hormonal) disorders:

• Diabetes mellitus - occurs mainly in older animals - other key signs include increased thirst,  increased urination and weight loss
• Hyperthyroidism - most commonly seen in older cats - other key signs include weight loss and increased activity
• Cushing's Disease - hyperadrenocorticism - occurs in older animals - other key signs include increased thirst and increased urination, hair loss and development of a distended abdomen

Also, gastrointestinal diseases :

• Pancreatic disease ( eg pancreatic atrophy) - other key signs include diarrhoea and weight loss
• Malabsorption syndrome -  occasionally causes an increased appetite
• Disorders of the oesophagus (eg megaoesophagus) may lead to an increase in appetite if the food is regurgitated - something which may not be noticed by owners if it occurs outside.

Other diseases that cause an increased rate of use of energy (eg cancer) may lead to an increase in appetite - even though the animal continues to lose body weight.

And, behavioural causes

In both cats and dogs excessive appetite due to unknown causes has been reported. In some breeds (such as the Labrador Retriever) it has been suggested by some authors that there may be a genetic predisposition to eat excessively and therefore to develop obesity.

And bad feeding practices

The control of food intake is extremely complex. (see satiety) but it is well documented that bad feeding practices can induce polyphagia. Animals fed ad libitum - that is with continuous access to unlimited amounts of food - are likely to overeat, and so are predisposed to develop obesity. Also, owners feeding frequent tit-bits and treats can induce overnutrition as can feeding very palatable  foods.

Sometimes an increase in appetite can be caused by the administration of drugs eg corticosteroids, or diazepam.

Consequences of polyphagia

Obesity  - except in the case of gastrointestinal disease or diabetes mellitus when weight loss is likely to be seen.

Avoid bad feeding practices. If there is an underlying disease process treat it appropriately. Modify undesirable behaviour. Prevent access to excessive amounts of food.

Updated October 2013