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What is Fasting?

by | May 26, 2020 | FAST FACTS

According to the dictionary, fasting is the abstinence from all or some kinds of food or drink. But there’s actually way more to fasting than Merriam Webster can help us with. In the real world of fasting, however there are so many ways to fast, different types of fasting, new methods and various applications that one definition can seem contradictory or unclear at best.   

Let’s break it down and define what fasting is and what fasting is not so we can better understand how to incorporate fasting into our life. 

The varying definitions of fasting

  • There’s physiological fasting, where the body’s growth pathways are inactivated due to a shortage of nutrients. Ketosis and autophagy are hallmarks of physiological fasting.
  • There’s water fasting, which is in line with the dictionary’s definition. No food; just water and no-calorie beverages.
  • There’s intermittent fasting, which is refraining from food on regular days throughout the week. (Some of these fasts, such as alternate-day fasting and 5:2 allow up to 600 calories for fasting days.)
  • There’s time-restricted eating, where you fast for part of the day and eat the other part.
  • And there’s fasting with food, also known as The Fasting Mimicking diet, which is a scientifically formulated diet package that tricks the body’s nutrient sensing pathways into thinking that you’re fasting. This creates the conditions for physiological fasting – minus the growling stomach!

 And within these definitions, there’s a whole world of varieties that make fasting one of the most accommodating, versatile, and popular lifestyle changes for your health.

What fasting isn’t

Fasting is not starvation.

Scientists and researchers have used the words ‘starvation’ and ‘fasting’ interchangeably, but this misusage has fostered in the mind of the public that fasting is somehow harmful to the body – somehow related to…starving*.


To be clear, starving isn’t a desirable thing. The word itself derives from old english and dutch words for “to die” and “to be rigid”, both of which are bad. Starving is malnutrition of the body; it’s the precursor to death. And most of the time it’s not intentional.

Fasting, on the other hand, is a very good thing. It derives from Germanic words that meant, “to have firm control over oneself” – discipline being the root of all good things.

Fasting is the rejuvenation of the body through the intentional abstinence of food, or through limiting food in order to mimic physiological fasting. There is no malnutrition during a fast! This is because the body has sufficient stores of fatty acids (from body fat) and amino acids (recycled from damaged or diseased tissue) to last for weeks and even months without deterioration.[1]

Finally, fasting is not calorie restriction.

Though it’s common for intermittent fasting to create a calorie deficit, that’s not the whole point of fasting. The point is to give your body a break from the constant onslaught of food that we call ‘normal life’ so that your cells can function optimally.

Many people definitely want to lose weight. And for them, it’s a good idea to reduce calories occasionally. But science has shown that prolonged calorie restriction actually decreases your body’s metabolism (and makes rebound weight gain almost inevitable).[2] Research in mice even shows many fasting benefits may be achieved without reducing calories at all.[3]

Bottom line: even though fasting sometimes leads to calorie restriction, you don’t have to reduce calories to benefit from fasting.

How to fast

Most forms of fasting allow for black coffee and herbal teas during the fast. (Ditto for electrolytes including potassium, magnesium, and sodium.) Some even permit up to 600 calories per day.

How should you fast?

That’s another question. But we can help you determine that! Just read our article, ‘How to Choose a Fasting Method.’ 

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[1] Energy Provision and Tissue Utilization in Prolonged Fasting

[2] Changes in Energy Expenditure Resulting from Altered Body Weight

[3] TRE in Mice Improves Survivability Independent of Calorie Restriction