How Much Should I Eat? The Health Benefits Of Fasting

Wednesday 12th Aug 2020 |

What constitutes a healthy diet? Most of us instantly think of pre-industrial — and even pre-agricultural — unprocessed meat and vegetables. And for good reason.

Most of the food we eat today is sprayed with chemicals for mass production and international shipping, and for preservation reasons. But there is another aspect of the pre-agricultural age that almost all of us have abandoned — and that is fasting.

The OED definition of fasting is to “abstain from all or some kinds of food or drink”. That’s the modern definition. The pre-agricultural one is probably the second variant of the word, also in the OED: “to be deprived of all or some kinds of food”. 

In the pre-agricultural world, it was common to go for long periods of time without food. That is why, when there is plenty of food about, we tend to gorge on it. This reaction is the body taking preparatory measures for the next eventual spell of food deprivation. Living in a world where food deprivation was common might sound unpleasant, but recent research has shown that it was actually beneficial.

Eating less & longevity

Last year, David Sinclair of Harvard University, one of the world’s leading gerontologists (age researchers), published his book “Longevity: Why We Age and Why We Don’t Have To”. In it, he stated that the most important thing to do in order to live a long and healthy life is to eat less. 


Eating less does not mean starving oneself, or being malnourished. It just means going hungry from time to time. Sinclair believes that all life on Earth has inherited a survival circuit that modulates how we age. This survival circuit kicks into a “repair” mode whenever the body is under stress, and works to repair broken DNA. A consequence of this efficient DNA-repair response is decelerated ageing. 

One of the ways to place the body under stress is to feel hunger. Whenever the body detects hunger, it begins planning for the worst, hunkering down and repairing DNA; boosting cellular function and the immune system. 

The benefits from the survival circuit come from implementing mild stress. Obviously too much stress is negative and damaging to the body. Starving oneself is unhealthy. But mild stress, such as feeling the twang of hunger, isn’t.

How much should I eat?

There are a few fasting diets that are thought to be very effective. They are:

·     The 16:8 diet — 

These numbers refer to the time. Followers of this diet tend to skip breakfast and have a late lunch (4pm) and slightly later evening meal (8pm). For most people, breakfast is probably the easiest meal to skip. Although age old wisdom suggests it’s also one of the most important to consume.  

·     The 5:2 diet — 

This intermittent fasting diet recommends that a person should eat regular amounts for most of the week, but on two days should only eat 75% of their daily recommended calorie intake. That is where the five-two comes from.  

·     The ‘Eat-Stop-Eat’ — 

Another type of (more dedicated) intermittent fasting is to fast for an entire week on eating minimal calories, and then resuming regular calorie consumption the following week; rinse repeat. 

Sinclair himself admits that — even though his goal is to extend longevity to the max — going hungry isn’t much fun, and that he cannot really follow the rules. Instead he chooses to miss arbitrary meals every now and then, such as breakfast. Frequently (but far from always) feeling hungry is a good thing. 

If it is not possible — or if the thought of missing a meal is too undesirable — try eating small amounts instead. Amounts don’t satisfy the hunger cravings, and maintain a state of calorific want. 

Obvious benefits of fasting

Aside from holding the key to greater long-term health, there are a plethora of other reasons why fasting is beneficial. The obvious is that food abstinence places less of a burden on the world’s resources. It is also, unsurprisingly, cost-effective. As eating less drives down the cost of the weekly supermarket shop.


Fasting also works well as a vegetarian-orientated diet. While it is possible to get all of one’s amino acids from plants, it is difficult. It is far easier, gram-for-gram, to meet the daily amino acid requirements from meat consumption. Meat-eaters often consume far too much of the necessary amino acids. Eating plant-based proteins instead, tactically, delivers enough amino acids for healthy function, but not enough to prevent the survival circuit from switching into mild stress mode. This in turn can mimic the benefits of fasting, even during consumption. If you’re considering a carnivorous diet. This is a list of healthy foods for your body. The carnivore diet consists of consuming predominantly meat, fish, and other animal products while completely avoiding any plant-based meals. It is high in fat, moderate in protein, and low in carbohydrates. You can check also the pros and cons of the carnivore diet.

Is fasting normal?

The quick answer is: yes. Human beings have been fasting — from both food abstention or deprivation — since the dawn of existence. In fact, fasting is so normal and commonplace that calorie restriction works on almost all life on Earth. Even yeast cells, artificially cultivated in the lab, will grow healthier and better if they consume less.

If Sinclair’s theory about the ancient survival circuit is correct, then intermittent fasting is a key strategy that enables reproductive and evolutionary success. It is, after all, only in the last century or so, that we have had access to an abundance of food, and that obesity has become a problem. It is the current situation of overconsumption that is not normal, not the other way around. 

About the author

Eliza Cochrane is a copywriter for GBS Clinic. She has written extensively about the health benefits of fasting, along with other issues to do with popular science, health and medicine on her website. 

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