Starvation, or chronic calorie restriction, can indeed promote autophagy in the body. However, there is no clear answer to how long it takes to start the autophagy reaction in the human body.

The word autophagy comes from the Greek, where “auto-” means “self,” and phagy comes from “phagein,” meaning “to eat.” So autophagy does mean “self-eating,” and it’s fair to say that you eat yourself.

But it’s a concept in cell biology that began in the 1960s, when researchers observed that cells could wrap up parts of themselves, send them to acidic lysosomal sites for degradation, and then recycle the resulting products. It’s like taking an unwanted Lego set and breaking it down into small pieces so you can assemble new shapes.

Japanese scientist Yoshinori Ohsumi has made important contributions to the field of autophagy. He set up his own laboratory in 1988 and then focused his research on the degradation of proteins. He found that if you put yeast cells in a state of starvation, they will initiate autophagy, digestion of the parts they do not need, to maintain the necessary physiological response to keep themselves alive.

This is a bit like the story in the ancient book, “cut the stock and Fengjun”, in order to prevent the later Jin Gong Wen Chong Er from starving to death, Jie Zitui cut off a piece of meat from his own thigh and made soup for Chong Er to supplement his nutrition. I knew it was robbing Peter to pay Paul, but I had to do it.

Ohsumi then discovered a number of genes that are critical to autophagy, and then revealed that autophagy is a complex process that is tightly regulated by cells and is the result of natural evolution. And not just yeast, but in human cells, there is almost the same autophagy reaction.

Thanks to Ohsumi and other scientists studying autophagy, we now know that autophagy controls cells to degrade and recycle their own components to provide them with energy or bring new raw materials to their metabolism.

What’s more, autophagy is linked to our health – it can eliminate bacteria and viruses that invade cells, it can allow embryos to develop properly, and it can fight cell aging by removing damaged cell contents. If the autophagy function is disrupted, it can cause diseases such as Parkinson’s disease and diabetes.

More than 50 years after the concept of autophagy was proposed, Yoshinori Ohsumi made us aware of its important role in physiology and medicine. It is for this reason that in 2016, the Nobel Committee awarded the scientist the Nobel Prize in Physiology or Medicine for his “discovery of the mechanism of autophagy.”

Starving for 16 hours

Can you initiate autophagy?

In Ohsumi’s study, by starving yeast, they can initiate their autophagy response. But in the human body, is it really possible to start autophagy after starving for 16 hours, as popular Internet information says? The problem is complicated.

According to the Cleveland Clinic, a well-known hospital, in animal studies, if you starve for 24 to 48 hours, you can basically start their autophagy response. In humans, it is clear that starvation or long-term calorie restriction can indeed promote autophagy. However, due to the lack of data, there is no clear answer to how long it takes to starve to induce autophagy.

This is not to say that there has been no research in humans. A 2018 review paper on autophagy listed 35 studies on autophagy, of which only three were from humans. In these studies, the time required to initiate the autophagy response varied, with the shortest being 36 to 72 hours and the longest requiring calorie restriction for up to 3 to 15 years. As for the 16 hours said on the Internet, there is no clear source and basis.

In addition, in animal models, autophagy has been shown to have health benefits by removing damaged parts of cells, cleaning up faulty proteins, or eliminating foreign pathogens. So now the medical community is also developing drugs that target autophagy, hoping to use it to treat disease.

Starving for 16 hours,

Can you really lose weight?

Interestingly, the 16 hours mentioned in the online message are related to another popular research topic. This involves a concept developed in recent years called “intermittent fasting,” which involves concentrating your meals in just a few hours each day and starving yourself the rest of the time. The most common “intermittent fasting” method is exactly 8 to 16, that is, eating is concentrated in 8 hours (such as 9 am to 5 PM), and the remaining 16 hours do not eat.

This method has achieved great success in animal experiments, proving that in addition to helping experimental animals lose weight, it can also improve the physical function of animals, and even prolong life.

A 2019 study published in the journal Cell found that such “light fasting” reduced the number of monocytes, which produce a variety of inflammatory cytokines that can induce chronic inflammation, in mice and humans. In the animal disease model, the mice with intermittent fasting for 4 weeks did improve significantly.

In January, a study in the journal Cell Metabolism found that intermittent fasting in mice helped to reshape the expression of genes throughout the body, leading to a more synchronised circadian rhythm in most tissues throughout the body, which also marked an improvement in metabolism.

Other studies have revealed that it’s not only important to be hungry, but also to pick the right time to be hungry. A 2021 study in fruit flies found that only flies that started starving at night and stayed hungry until noon the next day experienced significant benefits from being hungry and lived longer. On the contrary, if it is “eating late at night”, even if the hungry time is the same every day and the intake of food is the same, the fruit fly will not get the benefits of hunger.

This time-related hunger is thought to be linked to autophagy. This is because animals have a biological clock in their bodies, and autophagy is most active at night. If food is consumed at night, the body will be fooled into thinking that it needs to stay active and will suppress autophagy. Over time, the garbage in the cell will not be cleaned up in time, but it is harmful to the cell.

However, it should be noted that this theory seems reasonable, but it comes from animal experiments after all, and whether it can be applied to humans is still unknown.

Intermittent fasting method for weight loss is very general effect, reducing calorie intake is the core of effective weight loss, there is no authority of health institutions to recommend fasting weight loss.


There is a certain truth in the Internet news that hunger can initiate autophagy. But here are a few things to note:

First of all, not hungry for 16 hours, you can definitely start the body’s autophagy response, there is not much research to prove this. However, the fasting time that can initiate autophagy reaction confirmed in a few human studies takes 2 to 3 days, which may not be suitable for ordinary people.

Second, autophagy is a normal physiological function of the human body, and even if you are not hungry, you can start it by exercising or reducing calorie intake.

Third, “intermittent” hunger can indeed have a positive impact on the body, but the reasons are very complex, autophagy reaction is only part of it, and no authoritative health organization will recommend fasting to people to lose weight.

Finally, it should be emphasized that in order to become healthy, we also need to take scientific methods. They easily try not to eat or drink for a few days, just to “start the autophagy reaction”, may not be the method, but will damage their own body.