Medically known as polyphagia, there are a number of possible causes of constant hunger in cats, some more serious than others. Cats don't tend to be as food obsessed as dogs and most (but not all) will self- regulate their food intake. However, a common question asked by cat owners is 'why is my cat hungry all the time'?
Questions to ask include:
- Has my cat always been like this or has he suddenly got hungrier?
- Is he losing or gaining weight?
- How old is the cat?
- How many cats do you have?
How many calories should a cat consume in a day?
The answer varies depending on the age of your cat, also a pregnant or nursing female will have higher needs, as cats age they tend to slow down, and their calorie requirements may drop a fraction. But to simplify the answer, an adult cat should consume approximately 30 calories per pound, or 60 calories per kilo. So your average 10 pound (4.5 kg) cat should consume approximately 300 calories per day.
Is he getting enough food?
Following the above calorie intake, your cat's weight should remain consistent. To determine if your cat is overweight or underweight run your hands gently over his ribs. You should be able to feel the ribs but with a slight layer of fat over them. If the cat is obese, you may not be able to feel the ribs at all, if he is underweight the ribs will be prominent.
Another way I like to determine if a cat is getting enough food is by how quickly it is consumed, if it's all gone within the space of 5-10 minutes and is then back hassling for more, that would indicate to me that he's not getting enough.
So, what are the causes of constant hunger in cats?
- Not feeding adequate amounts of food.
- Psychological behaviour. Some cats can become food obsessed. This is especially true of cats who have encountered starvation or food shortages in the past such as former strays or feral cats.
- Multiple cats, where one is dominating the food bowl while another is missing out.
- Hyperthyroidism. Usually caused by a benign (non- cancerous) tumour on the thyroid gland which leads to an increase in thyroid hormone which speeds up the cat's metabolism and energy expenditure.
- Acromegaly. Caused by a tumour on the pituitary gland which stimulates growth hormones. Excess calories are burned up due to increased growth.
- Cushing's syndrome. An endocrine disorder which results in excess production of cortisol. Cortisol stimulates metabolism of fat and carbohydrates to increase sugar glucose levels. When blood sugar levels increase, so do insulin levels, which in turn stimulates the appetite.
- Insulin-producing tumours of the pancreas. Excess insulin produced by the tumour causes blood sugar levels to drop, which in turn stimulates the appetite.
- Diabetes. See hypoglycemia.
- Inflammatory bowel disease can lead to poor absorption of food, which results in increased hunger.
- Hypoglycemia is an abnormally low blood sugar level, there are several causes including diabetes and insulin overdose. This results in the cells being starved of glucose which is necessary for energy. The brain sends out hunger signals to obtain more food to feed the starving cells.
- Pregnancy. As the female cat's pregnancy progresses and her unborn kittens become larger, her food intake should be increased to support the growing demands of the unborn kittens.
- Lactation. A huge amount of calories are required to produce milk to feed a litter of kittens. A lactating queen should be given access to a high-quality kitten food and be allowed to eat as much as she wants during this time in her life.
- Exocrine pancreatic insufficiency. This condition leads to food not being absorbed as it should.
- Intestinal parasites which compete with your cat for food.
- Certain medications such as steroids can stimulate your cat's appetite.
How is the cause of constant hunger diagnosed?
Your veterinarian will perform a complete physical examination of your cat and obtain a medical history from you including the type of diet your cat is eating, how much, have you noticed any other symptoms, are there any other cats (or dogs) in the house and how are the dynamics between pets, has he always been this way or has the increased hunger happened suddenly, if the cat is a female, has she been spayed or is she nursing kittens, is the cat on any medications? Accompanying symptoms may give your veterinarian a clue as to the possible cause.
The most common medical causes of increased appetite in cats are hyperthyroidism and diabetes, which are more commonly seen in middle-aged to older cats. Diabetes often presents with increased thirst and urination and hyperthyroidism with increased activity, I once read the term 'cats on coffee' when describing cats with hyperthyroidism. Vomiting is common in cats with hyperthyroidism or diabetes.
If possible, bring along a stool sample for your veterinarian to evaluate.
If a medical cause is suspected, your veterinarian will need to perform some tests including:
- Complete blood count, biochemical profile and urinalysis to evaluate organ function. Hyperglycemia may be present in cats with diabetes. Hypoglycemia may be present in cats with insulin-producing tumours. Increased liver enzymes may indicate hyperthyroidism, diabetes or Cushing's syndrome. Increased glucose or protein in the urine can also point to diabetes.
- Thyroid function tests to check for hyperthyroidism.
- ACTH stimulation test to for Cushing's syndrome. This measures the ability of the adrenal glands to respond to a hormone known as adrenocorticotrophic hormone which is made by the pituitary gland and travels through the bloodstream to the adrenal glands where it stimulates the secretion of other hormones such as hydrocortisone from the adrenal cortex. The ACTH stimulation test measures the levels of cortisol in the blood before and after an injection of synthetic ACTH.
- fTLI ) feline Trypsin-Like Immunoreactivity to measure the concentrations of trypsin-like proteins in the serum. A low level indicates exocrine pancreatic insufficiency.
- Diagnostic imaging to evaluate the pancreas for insulin- producing tumours.
- Fecal flotation to check for parasitic worm eggs.
- Biopsy of the GI tract via endoscopy to check for inflammatory bowel disease.
How is the cause of constant hunger treated?
Treatment depends on the underlying cause. If it is behavioural, finding the cause and addressing will be necessary. For multiple cat households, feeding cats separately, even in different rooms if one is snaffling all the food. Feeding smaller quantities of food more often. Trying to slow down consumption of food by making your cat work for it, such as feeding raw/meaty bones or hiding food in kong like toys.
- Feline diabetes is managed by dietary modifications at first and if this isn't enough to manage the condition, your cat may have to have daily insulin injections.
- Hyperthyroidism is treated either by surgical removal of the affected thyroid gland(s) or radioactive iodine treatment which destroys the tumour while leaving the thyroid gland intact.
- Exocrine pancreatic insufficiency is treated by feeding pancreatic enzyme extract which are obtained from cow or pig pancreases. These help your cat to digest food. Switching to a low-fat, high fibre diet may also be necessary.
- Cushing's syndrome has several possible causes. If it is due to administration of corticosteroids, the medication may be gradually withdrawn. If a tumour is involved, surgical removal of the affected adrenal gland will be necessary.
- Inflammatory bowel disease is treated by dietary changes such as a highly digestible, low fat diet, as well as corticosteroids and antibiotics where necessary.
- A pregnant or lactating cat should be given a high calorie diet and free access to food. Once she has delivered and weaned her kittens, her appetite should subside.
- Surgery to remove insulin-producing tumours along part of the pancreas if necessary.