THE SCIENCE OF FASTING: Facts that will make you look smart around the dog park.

Young Husky pressing his paws against the hands of a woman

Now that you know what intermittent fasting is and why it’s important for your dog, maybe I can persuade you to go a little deeper into the science of fasting.

This is not just to be nerdy for the sake of it.

Things like;

  • the stages of intermittent fasting, 
  • the control of blood sugar and insulin, autophagy, 
  • and even a weird thing called hormesis,

help you understanding what happens 

when your dog fasts. 

And, you never know, people might ask you these things at the dog park (yes, I’ve seen that happen!).

Bear with me, I promise I’ll do my best to keep you awake.

The science of fasting: stages of intermittent fasting.

Researchers working on the science of fasting have found the following three phases of energy production upon prolonged fasting:

  1. Glucose is used quickly within the first 24 hours or so.
  2. Then, for only a few hours, some protein from muscle is transformed into glucose.
  3. Soon after, stored fat starts to be used as fuel in the form of ketones.

How do they know that?

Thanks to male emperor penguins!

Yes, the ones we see in all those National Geographic documentaries, like this one.

When in charge of caring for their eggs, they can endure up to 4 months without eating.

Well, someone had the patience and the courage to sit in extreme weather and investigate what was going on in the body of these animals during all this time without consuming any food.

As it turns out, depending on the amount of fat stored, penguins can go for as long as 100 days without eating while using their fat reserves.

Contrary to what one would expect, when they fast, only 4% of muscle is used for energy production while all the rest of energy comes from burning fat.

I know what you’re thinking. Penguins can do this because they’re weird animals that look like birds but swim like fish and walk like humans.

Some sort of mix between a bird and a fatty fish (they’re classified as birds!).

But here’s an amazing thing: the same sequence of events is observed in all other animals while fasting.

From yeast and worms, to dogs, monkeys, and humans, the scientific data indicates that all go through virtually the same physiologic, metabolic, and molecular adaptations when taking a break from eating. 

What this means is that the response of the body to fasting is a common mechanism conserved throughout evolution.

Millions and millions of years have been necessary to fine-tune a very precise, complex, and efficient protection system.

In this regard, you, me, and your dog are no different than fruit flies, mice, and even penguins.

This also means that all animals are well adapted to periodically going without food, and not adapted at all to constant eating.

It’s not only that animals can handle food restriction for a while, is that virtually all animals get healthier when fasting.

Fasting science

There’s still a lot to learn but scientists are working hard to figure out how the frequency and amount of food affects health and disease susceptibility.

What happens when your dog fasts?

1. Adaptive stress responses: mild stress protects against more severe stress.

Just like exercise is a stress for the body that makes it stronger, lack of food is a stress that makes organs and cells in your dog’s body more resilient.

The stress must be well dosed, not too mild, not too strong. 

Fasting, as well as exercise, will be beneficial only within a certain range of duration and intensity.

Some of the benefits obtained by intermittent fasting come from adaptation of organisms to stress.

The fancy Greek word used by scientists to describe this type of response is “hormesis”, that roughly translates to “to set in motion”.

Some prefer “preconditioning”. Or easier yet: “A mild damage that elicits a much greater beneficial response against future stress”.

Responsible in part for this newly obtained resilience upon stress is the internal production by the body of antioxidants.

They protect organs and cells from different insults and many studies in animals show higher production of antioxidants upon food restriction in muscle, heart, brain, liver, and other organs throughout the body.

2. Intermittent fasting, blood glucose, and insulin. From G to K.

One of the most studied physiological processes in the science of fasting that’s involved in its positive effects is the glucose-insulin system.

Glucose comes from the breakdown of carbs and sugars in a meal and is the preferred fuel of cells. 

Under normal conditions, the hormone insulin is produced by the pancreas when your dog eats, and glucose enters your dog's bloodstream. 

Cells can only feed on glucose if insulin “opens” the cells’ glucose receptors.

But this system, tightly regulated and optimized for survival in scarcity, can easily run into trouble under abnormal conditions of constant eating. 

Repeated bouts of glucose going into the blood with the inevitable insulin spikes that follow can make the cells become “resistant” and don’t respond anymore to the signals.

If things go off the rails, like they do in diabetic individuals, glucose-dependent cells become starved and glucose accumulates in the blood with serious consequences such as cataracts, kidney disease, and neuropathies.

Intermittent fasting keeps insulin low guaranteeing correct signaling to cells and the corresponding optimal use of glucose.

Excessive insulin production also has a more sinister role, the storage of any unused fuel in the form of fat. 

This is essential for survival in a world in short supply of food. 

However, when dogs are constantly eating, excess fat accumulates quickly and contributes to a myriad of metabolic dysregulations.

A healthy effect of fasting regularly or long enough is the transition from fat storage to fat burning. 

Fat is broken down into ketones in the fasted state, with powerful benefits on cells such as neurons in the brain.

According to this research, dogs seem to be especially well adapted to fasting since it takes longer for them to start producing ketones.

3. Reduced inflammation and damage control.

The immune system is a highly sophisticated army of cells and molecules exquisitely regulated whose main job is to protect the body from outside attacks such as viruses, bacteria, and injuries.

When a threat is detected, a well-orchestrated response, called acute inflammation, takes place and it’s aimed at getting rid of the intruder and heal damaged tissues.

Such response is so powerful that it needs to be controlled quickly to avoid harm to the very same organs it is protecting.

When the body keeps sending its soldiers to war even in the absence of external danger, chronic inflammation occurs.

If chronic inflammation persists, it can cause or worsen an array of common chronic diseases.

One of the reasons why this can happen is when a dog’s organism is exposed to excess supply of energy and nutrients.

Overweight and obesity, major health problems not only in dogs, but also in cats and people, are known to promote chronic inflammation.

Aging and its accompanying ailments are also driven by persistent inflammation.

Diabetes, cancer, cardiovascular, autoimmune, and neurodegenerative diseases, have all been linked to damage from chronic inflammation.

Simply by pausing the intake of food for a little while, your dog’s body can lower chronic inflammation or prevent it all together, slowing the development of chronic disease.

Chronic inflammation infographic

4. Autophagy: intermittent fasting and cell repair.

Cells possess a superpower: a process to clean out and discard their dysfunctional and damaged parts such as membranes and proteins.

This process is called autophagy, another word from the ancient Greek, of course. 

“Auto” means self and “phagein” eat, resulting in the daunting term “self-devouring”.

Despite its name, this mechanism is essential for the proper functioning of cells inside the body.

Amazingly, the goal of the process is to recycle the components and regenerate newer and healthier cells.

It literarily destroys to rebuilt better. 

Just another demonstration of Mother Nature’s wisdom.

However, autophagy is turned off when an organism is put in “growth mode” by a steady supply of energy and nutrients.

Aging is another factor that progressively prevents the correct recycling of damaged cell parts.

When autophagy is turn off, cell debris are left unremoved, they hang around and cells are harmed. 

One example is Alzheimer’s, in which a buildup of malfunctioning proteins occurs in neurons in the brain.

A similar pathological process occurs in the brains of senior dogs.

Fasting promotes autophagy and “cleanses” cells of damaged molecules in many tissues including muscle, kidney, and liver.

The science of intermittent fasting explained!

That’s it, you made it!

This’s all you need to know to impress everybody at the dog park and maybe even at the yuppy hour.

More importantly, it might help you consider fasting for your dog.


Write them down in the comments section below. 

I’m always happy to talk about the science of fasting.


Fasting induces the following processes to improve your dog’s overall health:

Reduced inflammation and increased antioxidant production.

Cellular repair through autophagy.

Control of blood glucose and insulin.

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  • Good detailed explanation about fasting, I knew fasting is good for us humans but wasn’t aware about the benefits it has for pets.

    D. Crane on
  • This is the clearest explanation about how fasting works that I have ever read! Although I don’t currently live with a dog, I do fast and I think everyone and their dog should, too! Thanks, Pedro!

    Deborah on

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