Medikologia / Health  / The Effects of Intermittent Fasting On Your Body: What Research Has To Say

The Effects of Intermittent Fasting On Your Body: What Research Has To Say

Did you know that certain eating patterns may enhance your cellular functions? Yes, like an organic, all-natural booster steroid with minimal side effects. 

The thing is, research shows when placed under mild physiologic stress (i.e. fasting) cells are able adapt and strengthen in order to survive. But the question is what are these changes? What kind of cellular and molecular alterations occur? Some health professionals even consider fasting as a newfound elixir for cancer, diabetes and even Alzheimer’s disease!

Is that even possible? 


To answer these questions, we’re gonna take a glimpse of what research has to show about dietary restriction and its effects on the body. We’ll be separating the wheat from the chaff and educate you on what intermittent fasting can do and what it cannot do. So sit back, fasten your seatbelt, and learn what science has to say!

Note: Since studies done on fasting and dietary restriction present with similar results, this article will use the terms “dietary restriction”, “intermittent fasting”, and “fasting” interchangeably to avoid confusion.


A Walk In The Past

Fasting isn’t a new thing. For centuries it’s been a normal practice in various cultures and religions. Christianity, Islam and the like, practice in one way or another a form of dietary restriction. But it’s only been for the past 100 years or so when scientists began to take an interest in this eating approach. And over the last decade, researchers have accumulated a large body of evidence regarding its effects on different biological life forms such as yeast, bacteria, insects, mice, monkeys, and of course…humans. And what they discovered was astonishing: under dietary restriction, living cells react in certain ways that strengthen, modify, and even prolong systemic functions. 

Below are two main response systems research can tell us as of today:


1. Enhanced Metabolism

Metabolism is a term used to describe chemical reactions that maintain the present state of cells and living organisms. In simple words, it’s everything that happens inside your body in order to maintain balance and keep your heart rate, temperature, breathing, blood pressure, body composition etc. within a certain range. 

Now, what do we mean when it’s enhanced by fasting? Does it mean your heart rate increases? Your temperature rises? And blood pressure hits the ceiling?

Not really… 

This is a term that encompasses various chemical reactions, but in the context of dieting the nutritional component is affected the most. And to understand that, it’s important to grasp how normal metabolism operates. 

Here’s an oversimplified explanation (and trust me, when I say oversimplified, it’s an understatement):

“Glucose”, also called a sugar or carbohydrate, is the basic source of energy that our body uses to carry certain functions. And It’s essentially derived from foods such as potato, bread, or pasta. When ingested, it travels through blood and gets stored in 3 different places. First, in the liver under the form of glycogen (a special molecular configuration that allows maximum glucose storage), second, in skeletal muscles (as glycogen), and lastly, when the tanks are full, as triglycerides (TGA) in adipocytes (a.k.a. fat cells). 

And that happens everyday after each carb-abundant meal. For example after breakfast, glucose gets released in the blood and stored in the liver. Hours later, just about when blood sugar decreases, another dose of carbohydrate comes from lunch. Then again after dinner. Thus, keeping the storage sites full throughout the day (provided you’re eating a moderate amount of carbohydrates every meal).

However, at night things work in a slightly different way:

After your last meal, as soon as blood glucose drops, the liver releases sugar (remember how it stores glucose in the form of glycogen? Now the reverse happens, a process known as “gluconeogenesis”) to keep energy supply constant while you sleep. Then at breakfast, the cycle repeats, and the liver rebuilds glycogen on your first carb meal.

This whole process of storing energy (i.e. glucose into glycogen) and releasing it (i.e. glycogen into glucose) is essentially how things work in human metabolism. And it’s called anabolism (building) and catabolism (breaking down). 

So what’s the deal with intermittent fasting? Does it change how nutrients gets stored and released?

Well…not really. What changes is the timing and duration of release.

Remember how things work differently at night when the liver releases glucose to keep a constant supply throughout your sleep? 

What happens is, after an overnight fast, liver glycogen is more or less depleted. And by the time noon arrives, the best part happens:

Glucose from skeletal muscles and TGA breakdown from fat cells kick in.

Scientists coined this process “metabolic switch”, which is a phase wherein the body shifts gear and enhances metabolism, particularly fat. And this takes place after depletion of liver glycogen when adipocytes release fatty acids into the bloodstream. This is the stage where the body literally uses fat as an energy source, a process called “fat oxidation”, which occurs roughly 14 to 16 hours after the last meal (just about noon time if your last meal was between 6pm to 8pm). 

Hence, in essence, fasting for at least 16 hours will activate the metabolic switch and begin oxidizing fat for usage as an energy source, thereby leading to an increase in metabolic rate. 

Yikes! That was one heck of a ride. Now let’s go to the 2nd type of reaction.


2. Increased Protective Mechanisms and Lifespan

The other reaction is enhancement of protective functions. 

There are 3 mechanisms I’ll share in the following paragraphs, but in reality, there’s a lot more researchers have discovered. So I limited the article to 3 benefits since these are the most discussed among health gurus. But if you want to know more, check out our infographics about the benefits of intermittent fasting.


The Body Increases Its Resistance to Reactive Oxygen Species

Reactive Oxygen Species (ROS) is a term that describes a group of unstable molecules and free radicals with the potential to damage human cells, specifically, by altering a cell’s DNA/RNA. Normally, at low levels, they act as signaling molecules for important body functions, but since we live in an imperfect world, the environment around us (i.e. stress, radiation exposure, etc.) enhances ROS production, hence placing us at higher risk for certain pathologies like neurodegeneration, carcinogenesis, atherosclerosis, diabetes, and even aging. 

So what does IF have to do with it?

Research shows that across different life forms, fasting enhances protection against oxidative stress. For examples, studies made by Longo et al. in 1997 and Wei et al. in 2008 show that in yeast, a reduction in glucose at about 2 to 0.5% induced by fasting enhanced this protective mechanism. Worms also produced similar results by resisting oxidative stress through RHEB-1 and TOR signaling (Weinkove et all., 2006; Hinjoh et al. , 2009).

In flies, defenses from ROS was through the PI3K/Akt/dFOXO3 pathway (Tettweiler et al., 2005)., while in mice, protection was shown by an improvement in survival from a drug known to promote oxidative stress, namely, etoposide (Raffaghello et al., 2008).


The Body Slows Down Tumor Growth

Oncogenic mutations (mutations in the DNA that lead to cancerous cells) are the etiologic reason of how cancers develop. This happens when hyperactivation of certain molecules responsible for cellular growth (i.e. IGF-I, Akt, Ras, and mTOR) occur. Normally, these guys are well behaved and in fact should promote growth in almost every cell, especially skeletal muscle, bone, kidney, cartilage, liver, nerves, hematopoietic and lung cells. However, when mutations happen, even tumor cells (which under normal conditions are kept in check) develop, eventually becoming cancerous ones.

Now, scientists discovered that dietary restriction (DR) prevented tumor growth in mice (Moreshi, 1909), and ever since then, various studies were done across different animals showing that DR reduces the progression of tumor (Tannenbaum, 1945; Hursting et al., 1994). For example, studies done by Weindruch and Walford in 1982 and Weindruch et al. in 1982 showed that spontaneous cancer incidence was reduced to more than 50% in rats using an undernutrition without malnutrition dietary approach. In another study done on monkeys, a 30% dietary restriction was also shown to reduce cancer incidence by 50% (Colman et al., 2009). However, it’s only been in 2009 that this dietary method was discovered to be effective only in specific types of cancer (Kalaany and Sabatini, 2009), and that progression isn’t stopped, but only delayed by fasting (Mukherjee et al., 2004; Bonorden et al., 2009; Shelton et al., 2010).

Too much scientific jargon is getting your brain saturated, isn’t it? 

Don’t worry. We’ll be wrapping things up in a bit.


The Body Prolongs Cellular Life Span

Extension of life span is also proven in different studies. For instance, E. coli (a type of bacteria) was shown to survive 4 times longer when exposed to caloric restriction (Gonidakis et al., 2010). In yeast, a 2 fold in lifespan extension was observed under similar nutritional requirements (Longo et al., 1997), with an additional boost in resistance to multiple stresses (Longo et al., 2012).

In another study, nematode  C. elegans (a type of worm) also had a major increase in lifespan by giving it little or no food (Kaeberlein et al., 2006). And in flies (Drosophila), similar results of longevity extension were also noted (Piper and Partridge, 2007).

How about in humans?

There are four major factors when it comes to lifespan extension that we have to consider, namely: oxidative stress, inflammation, accumulation of dysfunctional proteins, and elevated glucose, insulin and IGF-I. 

As we’ve previously discussed, free radicals (which contribute a lot to oxidative damage) are counteracted by the effects of caloric restriction in different animal models. In humans the same results can also be seen. For example, a study made in asthmatic patients put on alternate day fasting was shown to decrease markers of inflammation and oxidative damage within 2-4 weeks (Johnson et al., 2010). Another similar study done on overweight women at risk for breast breast cancer also exhibited a reduction in inflammation and oxidative stress (Harvie et al., 2011). 

As for dysfunctional proteins, a process known as autophagy (the body’s way to recycle dysfunctional organelles) was also seen as an anti aging mechanism, together with a decrease in mTOR pathway (another factor that predisposes biologic life forms to a decreased lifespan) (Harvie et al., 2011; Sengupta et al., 2010).

How about elevated glucose, insulin and IGF-I (insulin growth factor 1)? 

A study done by Fontana et al. in 2010 had shown that fasting for 3 days or more causes a 30% reduction in circulating insulin, glucose, and IGFI. While in humans, 5 days of fasting also causes a reduction of about 60% in IGF-1 and5 fold increase of IGFBP1 (a molecule that inhibits IGF-1 production) (Thissen et al., 1994)

Is it intermittent fasting the ultimate panacea?

If you’ve been living long enough to browse through the web, scroll down facebook posts, or even watch health related videos on youtube, you’ve probably seen health gurus and experts claiming how IF may cure diabetes, Alzeihmer’s, or even cancer. 

But, is that really true? 

If we look at the research we have today, it’s fairly easy to say how this dietary approach can serve as an alternative treatment for various pathologies… after all, fasting does provide certain benefits. However, a large body of studies comprises animal models, with only few human studies as of today. And when it comes to medical research, human trials are the last stage before physicians can approve and prescribe specific modalities of treatment. 



Therefore, while fasting provides healthy effects on biological life forms, claiming it as a cure for medical conditions is an overstatement due to limited studies in humans. 

But aside from that, it can be used as a lifestyle approach to stay and feel healthy, provided you don’t suffer from gastrointestinal or metabolic conditions, in which case consulting your local Doctor would be a safer approach.

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