What is Fasting?

Fasting is not the same as starvation. With therapeutic fasting, nutrient intake is enough to maintain vital tissues, like heart and muscle. Ideally, there will be an additional supply of co-factors for liver enzymes required to deal with the breakdown of fat and release of toxins that occurs. Starvation occurs when there are no reserves left in the body and insufficient intake of nutrients, so that vital tissues are broken down.

Fasting has shown benefits for human and animal health as well as a lengthening of lifespan. (1)

I've been on a diet every day since I was nineteen, which basically means I've been hungry for a decade”.

Julia Roberts as Anna Scott in the movie, “Notting Hill”

How Long Should I Fast My Dog?

Your dog may naturally fast, not eating for a day or two. If not, a 24 hour to 48 hour fast intermittently every week or two will suffice. An easier intermittent fast schedule and less guilt-ridden for the pet parent is to restrict your dog's food intake to an 8 hour time frame every day. For example, if you feed in the morning at 8 AM, feed him again at 4 PM. This restricts his eating to an 8 hour period of time. Then he will have no food at all until 8 AM the following day. This gives your dog 16 hours for fasting time. 

  • If your dog is on daily meds, like insulin have to give your dog drugs (insulin, thyroid meds etc.,) use the daily restricted food intake method of intermittent fasting use the 8 hour feeding time period

Our ancestors, both the dogs and us, lived through cycles of feast and famine. If we are constantly in feast mode, the body is not able to conduct much of it's repair and rejuvenation processes and so disease takes hold and health declines. A period of regular fasting helps the body to heal again.

Here are some helpful hints:

  • Don't fast puppies
  • Use intermittent fasting for sick, adult or old dogs
  • Always use a 24 - 48 hour fast when transitioning to a raw food diet
  • Always have pure water available for your dog
  • Don't feed any other food at all during the fasting time period. This treats!
  • If your dog is on daily meds, like insulin have to give your dog drugs (insulin, thyroid meds etc.,) use the daily restricted food intake method of intermittent fasting use the 8 hour feeding time period
Looking Into the Past

Our dogs and their humans evolved hungry

Wolves, the dog’s closest living relative, are a window into normal dog physiology (before modification by kibbled dog food, dog sweaters and doggie beds). An ongoing study of wolves reintroduced to Yellowstone National Park confirms that they “are adapted to ... feast-or-famine foraging.” When hunting is easy, packs make a kill every two to three days.

An elk is consumed in this order: first, organ meats, then major muscle masses, and finally bone and hide. In this case, at the end of the two or three day period, lower caloric value is consumed, and bones are eaten at the same time as hide, including the fur. This mimics to a certain extent the alternate high calorie/ low-calorie day diet used in one type of CRD.

In leaner times Yellowstone wolves have scavenged mostly bone and hide for several weeks at a time. This is more like a prolonged modified fast. (2)


Toxic Load Decreased

With little competition from substances absorbed after a large meal, the liver is able to fully process the released waste products and excrete them through bile, or release the processed products into the bloodstream for elimination through the kidneys, decreasing toxic load in the body.

Research on the favorable effects of intermittent fasting shows that during fasting, mitochondria down-regulate, with fewer free radicals released from them.(3)

This process, known as hormesis, may be the reason that fasting has been shown to decrease inflammatory molecules in so many different cell types. Inflammation underlies many degenerative diseases, and fasting has been shown to decrease the incidence of cancer, (4,5,6)  decrease or reverse arthritis, cognitive decline, type II diabetes (7), hypertension (8), dermatitis (9) and liver, kidney (10), and heart disease (11). 

One study showed its effect on improving age-related deafness (12).  This effect has been seen in rats, mice, rhesus monkeys and in humans. All studies cited included subjects on some type of CRD, and do not include obesity studies. A 25-year ongoing study in rhesus monkeys also showed a slower rate of muscle loss with age, with no apparent loss of bone density.(13)

Favourable Effects

Fasting for 48 hours or longer has been shown to protect normal cells, but not cancer cells, from toxic effects of chemotherapy (14). This has been used in some human chemotherapy patients to mitigate the side effects of chemotherapy. It is worth pursuing companion animal cancer patients.

An increased lifespan has been observed in Labrador retrievers.(15)

Fasting can create many valuable advantages such as: 

1. Elevating macrophage activity which will engulf and destroy bacteria, viruses, and other foreign material.

2. Allowing the digestive system to relax and let the body focus on other important bodily functions.

3. Allowing the body to regenerate briefly. It is amazing to watch a complete reversal of digestive symptoms such as upset stomach and diarrhea, as well as allergy relief.

In a nutshell, a domesticated dog is able to reap benefits by fasting. It can boost their metabolism, maintain a healthy appetite and weight, and optimize their overall health.

For best results you should start out slow by fasting once a month, and then increasing the fast eventually to once a week. The fast will give the digestive system a break and allow the body to regenerate and preserve the essential digestive enzymes from depletion.

When a dog’s body is allowed to focus on other metabolic activities, it conserves energy, detoxifies, and builds resistance to disease. 

When trying to decide if fasting is healthy or not, you might consider that fasting is not harmful in any way. Nature has spent fifty million years perfecting the mammalian enzymatic machinery to deal with lack. Just about every creature that ever existed in the history of the world missed a meal every now and then.

For dogs that are of proper weight and body condition, there is no compelling reason to fast. But when our company takes on new clients, we are usually dealing with dogs that are obese, suffering from allergies, depressed immune systems and in generally poor condition. In this case a fast might be just what the doctor ordered. (16)

Creator: Paul Raybold  

1. Johnson JB, Laub DR, John S. The effect on health of alternate day calorie restriction: eating less and more than needed on alternate days prolongs life. Med Hypotheses. 2006;67(2):209-11. Epub 2006 Mar 10.

2. Stahler DR, Smith DW, Guernsey DS. Foraging and feeding ecology of the gray wolf (Canis lupus): lessons from Yellowstone National Park, Wyoming, USA. J Nutr. 2006 Jul;136(7 Suppl):1923S-1926S.

3. Ristow M, Zarse K. How increased oxidative stress promotes longevity and metabolic health: The concept of mitochondrial hormesis (mitohormesis).Exp Gerontol. 2010 Jun;45(6):410-8. Epub 2010 Mar 27

4. Dogan S, Johannsen AC, Grande JP, Cleary MP. Effects of Intermittent and Chronic Calorie Restriction on Mammalian Target of Rapamycin (mTOR) and IGF-I Signaling Pathways in Mammary Fat Pad Tissues and Mammary Tumors. Nutr Cancer. 2011 Apr;63(3):389-401.

5. Seyfried TN, Kiebish MA, Marsh J, Shelton LM, Huysentruyt LC, Mukherjee P. Metabolic management of brain cancer. Biochim Biophys Acta. 2010 Sep 8. [Epub ahead of print.

6. Omodei D, Fontana L. Calorie restriction and prevention of age-associated chronic disease. FEBS Lett. 2011 Mar 26. [Epub ahead of print]

7. Mattson MP. The impact of dietary energy intake on cognitive aging. Front Aging Neurosci. 2010 Mar 8;2:5.

8. Rains JL, Jain SK. Oxidative stress, insulin signaling, and diabetes. Free Radic Biol Med. 2011 Mar 1;50(5):567-75. Epub 2010 Dec 13.

9. Perkins SN, Hursting SD, Phang JM, Haines DC. Calorie restriction reduces ulcerative dermatitis and infection-related mortality in p53-deficient and wild-type mice. J Invest Dermatol. 1998 Aug;111(2):292-6.

10. Wielinga PY, Yakala GK, Heeringa P, Kleemann R, Kooistra T. Beneficial effects of alternate dietary regimen on liver inflammation, atherosclerosis and renal activation. PLoS One. 2011 Mar 31;6(3):e18432.

11. Johnson op cit.

12. Sebastian C, Mostoslavsky R. SIRT3 in calorie restriction: can you hear me now? Cell. 2010 Nov 24;143(5):667-8.

13. Kemnitz JW. Calorie restriction and aging in nonhuman primates. ILAR J. 2011 Feb 8;52(1):66-77.

14. Raffaghello L, Safdie F, Bianchi G, Dorff T, Fontana L, Longo VD. Cell Cycle. 2010 Nov 15;9(22):4474-6. Epub 2010 Nov 15. Fasting and differential chemotherapy protection in patients.

15. Huck op cit

16. Robert Mueller, BSc, Pharm. is a registered pharmacist, author of “Living Enzymes: The World’s Best Kept Pet Food Secret”,

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