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Obesity is a major nutritional problem in
companion animals in the United States. Studies have estimated the
incidence of overweight and obese cats to range between 19 and 40%.
Obese cats are at higher risk for health problems compared to cat that
maintain ideal weight. Obese cats are more prone to diabetes, liver
disease, skin problems, urinary tract problems, and arthritis. As a
veterinarian specializing in cats, I find it more difficult to provide
proper medical care to overweight cats. During a physical examination,
it’s harder to feel the abdominal organs, more difficult to insert an
intravenous catheter or to obtain urine via cystocentesis (inserting a
needle into the bladder), and more challenging to obtain a good quality
x-ray in overweight cats. Routine surgical or anesthetic procedures
become more difficult, or even hazardous, when cats are overweight.
Diabetes is one of the most common
glandular disorders in cats. Cats, like humans, can develop two types of
diabetes. In type-1 diabetes, the pancreas in incapable of producing
adequate amounts of insulin. In type-2 diabetes, the pancreas produces
insulin, but the body does not recognize or respond properly to the
insulin.
The link between obesity and type-2 diabetes in well documented in both
humans and cats. An obese woman is nearly 13 times more likely to
develop diabetes than women within healthy weight ranges. In the U.S,
the incidence of type-2 diabetes rose an incredible 33% from 1990 to
1998. Overweight cats are twice as likely as normal cats to develop
diabetes. Obese cats? Four times more likely.
Treatment of diabetes typically involves giving insulin injections once
or twice daily, for the rest of the cat’s life. Type-1 diabetics do not
produce enough insulin, and therefore are dependent on insulin
injections to regulate their blood sugar. Type-2 diabetics, however, are
capable of making their own insulin and may not necessarily require
insulin injections. Overweight type-2 diabetics often respond to oral
medications designed to lower the blood sugar, and some may respond
simply to a change in diet. In many instances, a combination of oral
medication and diet change is needed. Unfortunately, there is no
simple method of determining which type of diabetes – type 1 or type-2 –
is afflicting a particular cat. Most type-1 diabetic cats have the
classic clinical signs: excessive thirst, excessive urination, ravenous
appetite, and weight loss, and tend to be thin or underweight. Most
type-2 diabetic cats have excessive thirst, urination, and appetite, but
the signs are not as severe as that seen in type-1 cats, and many type-2
cats are overweight. If a cat presents with mild clinical signs of
diabetes and is overweight, veterinarians should discuss with the client
the possibility that their cat is a type-2 diabetic, and that their cat
may respond simply to a change in diet, namely, a diet designed to
promote weight loss. Clients need to be informed of the risks involved:
delaying insulin therapy in a cat that is truly insulin-deficient may
lead to a condition called diabetic ketoacidosis (DKA), a potentially
life-threatening complication of diabetes.
For years,
diabetic cats were prescribed a diet high in fiber and low in fat.
Fiber is a complex carbohydrate. It is metabolized very slowly,
minimizing fluctuations in blood sugar, allowing for tighter regulation
of the diabetes. Overweight cats do respond to these low fat/high fiber
diets, losing weight in a fairly predictable fashion. Recent studies in
feline nutrition and diabetes, however, have led to a change in thinking
regarding the best diets for overweight and diabetic cats. It seems
even our cats are about to get caught up in the low-carbohydrate craze
that has swept the nation. For cats, though, it makes perfect sense:
cats are pure carnivores.
Cats have been fed a wide variety of diets since becoming domesticated,
apparently with little regard to what they, as carnivores, would
encounter in nature. Cats in the wild eat mice, and if you look at the
nutritional content of a mouse, what do you find? Mice are 3%
carbohydrate, 40% protein, and 50% fat. Yes, mice are low-carb snacks.
Dietary carbohydrates are not required by normal healthy cats.
Carbohydrates are physiologically essential – most cells in the body
normally utilize carbohydrates, in the form of glucose, as their main
energy source. But carbohydrates are not an essential dietary
nutrient. If carbohydrates are not provided in sufficient quantities in
the diet, dietary protein is utilized as the main source for glucose
synthesis. Cats, being strict carnivores, are well-adapted to
metabolizing protein, and they can convert protein to glucose for energy
pretty efficiently. Cats, however, are not very efficient at processing
carbohydrates. For glucose to be used by a cell, it must enter the cell
and undergo a process called phosphorylation. In most animals, this
requires the enzyme glucokinase. Cats lack this enzyme, and must use
another enzyme, called hexokinase. This enzyme is not very efficient in
cats.
Obesity occurs if a cat takes in more calories than it uses.
Carbohydrates consumed in excess of energy needs will be converted for
storage. How are these carbs stored in the cat? You guessed it: fat.
Recent studies suggest that cats fed diets that are high in protein,
high in fat, and low in carbohydrates are ideal for strict carnivores
like the feline. Diets like these help keep cats slim, and prevent
diabetes from developing. For cats with diabetes that are already
receiving insulin injections, and for newly diagnosed diabetics,
especially those that are overweight, a high protein/low carb diet may
be an essential component of diabetes therapy.
Feeding a high protein/low carb diet has become very easy, thanks to The
Purina Company and the Hill’s Company. Purina manufactures a
prescription diet called DM (for “diabetes management”) that is
high-protein/low-carbohydrate. More recently, the Hill’s company has
developed a similar diet called Hill’s m/d. Studies have shown that the
use of these diets can reduce blood sugar levels, enhance glucose
control, increase sensitivity to insulin, and lower the insulin
requirements of most diabetic cats. The most significant study was
described in the Summer 2001 issue of Veterinary Therapeutics.
Nine adult, client-owned cats with diabetes of at least four-months
duration were initially fed a high-fiber, moderate-fat canned diet for 1
to 2 months, to establish a standardization period. All cats were then
transitioned onto a high-protein, low-carbohydrate canned diet for the
three-month treatment period. A complete blood count, chemistry panel,
and several other blood, urine, and behavioral parameters were assessed
at the start, the midpoint, and the end of the study. Cats were
monitored closely during the treatment period, and insulin dosages were
adjusted as necessary. Cat owners were asked to maintain a diary to
record food intake, changes in their cat’s activity, drinking habits,
excretory habits, and any other significant observations.
The clients’ recorded
perceptions of appetite, activity, urination, and health showed a slight
improvement, and all cats did well during the treatment period. Body
weight remained stable throughout the study. The most significant
findings were related to the insulin requirements. The total dose of
insulin required to regulate the diabetes decreased significantly during
the treatment period. The daily dose of insulin decreased in 8 of the 9
cats. Remarkably, 3 cats no longer required any insulin at all to
control their disease! The response to dietary change occurred quickly,
during the first half of the treatment period
Because it is impossible to say for sure which cats will respond to a
high protein diet, and to what degree the insulin dose can be reduced,
diabetic cats that are being transitioned to these new diets need to be
monitored closely during the first few months, to ensure that
hypoglycemia (low blood sugar) doesn’t occur.
High protein/low carb diets are not suitable for all cats. Cats with
kidney disease should not be fed these diets, as high-protein diets have
been implicated in more rapid progression of kidney failure.
Obesity is a health risk for all indoor cats. Providing your cat with a
stimulating environment and plenty of play, as well as feeding a healthy
diet, is essential for keeping your cat’s weight in the ideal range.
Evidence now suggests that high protein/low carbohydrate diets may be
just the ticket for our carnivorous companions.
Updated 2/9/06
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