By Dr. Becker
Fasting is rarely mentioned these days as a health benefit for companion animals. It's difficult to find any discussion of the subject in current pet care information, online or off.
It seems to have fallen out of favor over the last decade or so. And I think I might know the reason.
When fasting for people and pets was popular back in the 1990's, I personally had experience with people who decided to fast all the 'wrong' types of pets, for example:
- A 4-month-old puppy who developed hypoglycemia
- A diabetic dog, fasted after a dose of insulin, who also developed hypoglycemia
- An overweight cat who developed hepatic lipidosis (fatty liver disease)
- A very elderly, ill Schnauzer who was already cachexic (wasting away)
Fasting is not a good idea for cats, especially if they're overweight (more about that shortly), and as a general rule, it's only safe for healthy adult dogs – emphasis on healthy and adult.
I suspect I wasn't the only pet healthcare practitioner who learned the hard way not every pet owner or guardian understands which animals can be fasted and which should never be fasted. And I think that is the reason there's so little mention of it in current pet health care literature.
If you're wondering about the health benefits of fasting for your own four-legged companion, I strongly urge you to talk with your holistic vet about whether it makes sense for your individual pet.
Therapeutic Fasting is Not Starvation
Therapeutic fasting involves sufficient nutrient intake to maintain vital tissues, organs and muscle, along with liver enzyme co-factors to help with fat breakdown and the release of toxins.
In contrast, starvation involves no nutrient intake and depletes all reserves in the body, at which point vital tissues begin to break down.
Fasting causes the body to metabolize fat. Waste products stored in fat are released. This waste not only includes breakdown products of natural substances the liver couldn't process, but also toxins absorbed from the environment, for example, chemical pest repellents.
Because the body is not being asked to digest and absorb large meals during a fast, the liver can more efficiently process the released waste products, which decreases the body's toxic load.
In an ongoing study of wolves reintroduced to Yellowstone National Park, researchers reveal that:
"Wolves are adapted to a feast-or-famine diet and can overcome periods without fresh carcasses through food caching, reduced activity, and scavenging old prey carcasses."
In other words wolves, close relatives to dogs, are to some extent natural fasters.
The same can't be said for cats, especially if they are overweight.
Why Cats Should Not Be Fasted
Feline hepatic lipidosis is a common disease among kitties. It's caused by an accumulation of fat in the liver, which prevents normal functioning.
I'll be discussing this condition in depth in an upcoming video, but for now just know that hepatic lipidosis is a very serious problem. It moves quickly and will result in death if it isn't caught early.
The condition is secondary to a number of other feline diseases. However, about half the cases of hepatic lipidosis have no apparent cause and almost always occur in obese cats whose appetites have decreased or disappeared.
According to Dr. Nancy Scanlan:
"The feline liver does not down-regulate during fasting and so there is less protein-sparing effect. Hepatic lipidosis can occur with as little as two or three days of fasting in a susceptible cat. So fasting should not be continued for more than a single day, if that long."
Some of my clients will do a modified feline fast for the healthy, mid-life cats in their care: providing a single meal in a 24-hour period, one day a week (verses 2 meals in a 24-hour period). Cats must pass a health exam prior to fasting.
Again, I highly recommend you to talk with your holistic vet if you're considering fasting your dog or cat.
An Alternative to Therapeutic Fasting for Your Pet: The Calorie Restricted Diet
A calorie restricted diet (CRD) is typically a diet reduced to 70 or 75 percent of normal daily caloric intake.
For example, if you have a 15-pound kitty whose normal daily calorie count is 220, you could reduce that amount by 25 to 30 percent and feed only 154 to 165 calories per day. You feed the same food, just less of it.
Intermittent fasting or long-term calorie restriction has been shown to have beneficial effects on free radicals, which decreases oxidative stress. It is the inflammation resulting from oxidative stress that is thought to be the primary cause of age-related degenerative disease.
In studies done with rats, mice, rhesus monkeys and humans, a CRD has been shown to decrease or reverse:
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Research shows animals on calorie-restricted diets have less degenerative disease, improved overall health and longer lifespans.
In a groundbreaking study of 48 Labrador retrievers from 8 weeks of age until death, 24 dogs were fed a 25 percent CRD and 24 control dogs were not. The results:
Compared with control dogs, food-restricted dogs weighed less and had lower body fat content and lower serum triglycerides, triiodothyronine, insulin, and glucose concentrations. Median life span was significantly longer for dogs in which food was restricted. The onset of clinical signs of chronic disease generally was delayed for food-restricted dogs.
These same dogs also showed fewer incidence and severity of osteoarthritis in joints and lived an average of 2 years longer than the control dogs.
A calorie-restricted diet certainly shows promise in certain instances, and especially for large breed dogs. As is the case with fasting, however, I strongly urge you to consult with your veterinarian if you're contemplating either a fast or a calorie-restricted diet for your pet.