A few days ago, Zhang Yun, an academician of the Chinese Academy of Engineering, mentioned in an interview,Eating eighty percent full and having hunger will activate the longevity gene; If you don't wear warm clothes and feel a little cold, you will also activate the longevity gene.On the surface, these two sentences seem to be a bit counterintuitive—we often use the phrase "hunger and cold" to describe a person in adversity, and hunger and cold, which everyone fears to avoid, can promote longevity?

In fact, despite some simplification, the message behind these two sentences has long been supported by research results, and the biology behind them has been clarified.

Hungry learning

Speaking of hunger, you may have heard of the concept of "fasting" in recent years. The definition of "hunger" in biological research is more precise and complex. A review published in Nature Aging in 2021 concluded: fasting scientifically belongs to the category of "intermittent diet", which can be roughly divided into several types -

Fasting every other day（alternate-day fasting，ADF）指一天正常吃喝，另一天只攝入水分；5/2 飲食（5：2 diet）指一周里有五天正常飲食，剩餘兩天只攝入 500 到 700 卡路里；

限時進食(time-restricted feeding, TRF) divides the day into two periods, limiting eating to the shorter period (usually 12-0 hours) and not eating for the rest of the day.

Other, more extreme approaches will:The fasting period is extended to 2-0 days, but this is usually rare.

In general, the key to intermittent eating is "intermittent", where you eat normally for a period of time and limit your calorie intake for a while. The "hungry" phase is key, as it initiates a switch in metabolic mode.

In most mammals, excess glucose is stored in the liver as glycogen.After a period of fasting, as blood sugar levels drop, glycogen is gradually depleted in the liver to maintain blood sugar. When the liver's glycogen stores are insufficient, the body switches its metabolic mode and turns to ketones and fats as a source of energy, which is commonly known as "fat burning".

Fat was originally used by our ancestors to store energy and protect against the cold during the winter months, when it was difficult to forage. However, with the continuous improvement of living standards, modern people are less hungry, eat too full, and continue to accumulate fat, resulting in an obesity epidemic. According to the World Health Organization（WHO）In 8 years, one in every 0 people suffers from obesity. As you gain weight, so does your risk of various diseases.

therefore"Burning fat" itself can reduce the risk of contemporary "affluence disease". Other studies have shown that this metabolic pattern can lead to better coping with stress and prolonging life.

In addition, fasting can activate the autophagic response in the human body through relevant cell signaling pathways in the body, promoting apoptosis of those damaged senescent cells. When you resume eating, the influx of nutrients promotes cell regeneration. In a sense, fasting, resuming the cycle of eating, is like giving cells a chance to renew and renew. In this way, the corresponding tissues and organs will also become younger and healthier.

The mystery of the cold

In the martial arts novel "The Condor Heroes", there is a magical cold jade bed, and those who sleep on it will feel that it is extremely cold and unbearable, and they must use their whole body strength to fight against the cold, even if they are practicing unconsciously in their sleep. After a long time, the internal strength will be successful.

Although this is a magical setting in martial arts novels, in recent years, researchers have become more aware of the benefits of cold for animals. For example, nematodes, which are commonly used model organisms, will have a shorter lifespan if they move from 15 degrees to higher temperatures. On the other hand, if you go to an environment of about 0 degrees Celsius, you can significantly extend your life.

In mice, the researchers saw similar results. Just an environment that is 5.0 degrees higher than body temperature is enough to shorten their lifespan. Conversely, if the environment is 0.0 degrees lower than body temperature, the lifespan of mice can be extended. These studies clearly show that there is an inextricable link between temperature and longevity.

Scientists are trying to find out why, also in Nature Aging, a paper published last year found thatLower temperatures can activate the proteasomes in nematodes to degrade disease-causing proteins that clump together. The same results were observed when they moved from nematodes to human cellsAt 36 degrees Celsius, this proteasome in the body's cells begins to activate, destroying proteins that are involved in disease. This may explain some of the benefits of the cold.

Other explanations are more simplistic and crude: in a low-temperature environment, the rate of all biochemical reactions will slow down, and the pace of aging will naturally be slowed down; In addition, low temperature can also promote fat burning, and a slimming can relieve a thousand sorrows.

These explanations all sound reasonable, but it needs to be pointed out thatOur understanding of the cold is still quite rudimentary, and there are still many mysteries to be solved.For example, a joint study by the University of Michigan and Huazhong University of Science and Technology in the United States has found that in adult nematodes, low temperature can activate a protein called TRPA16 located on nerve cells and fat cells, initiate a series of biochemical reactions, and finally activate the longevity gene DAF-0/FOXO.

Interestingly, in nematode larvae, the same environment can have the opposite effect. In fact, larvae living in warmer environments have a 20% higher lifespan. These seemingly contradictory data also tell us that there is much more to explore about the effects of temperature on living organisms.

The revelation of "hunger and cold".

Existing scientific research can only explain how organisms react to hunger or cold, and how it can potentially affect health, but cannot answer the question "why this is the case". There have been a lot of speculations about this.One explanation is that modern society is developing too fast and the body is not keeping up with it.

If we think of the human body as a smartphone, then the genome is our hardware that determines our performance ceiling; The stimuli from the environment, such as software, have undergone rapid upgrades and iterations over the past few thousand years. Today, we can sit in a climate-controlled office, reach for a variety of food and sugary drinks, and not have to run around like our hunter-gatherer ancestors.We single-handedly created a comfortable environment, but the body felt overwhelmed. Some of the so-called adversity that seems to be in the present day is closer to the environment that the human body is familiar with, so that it can return to a healthier state.

Of course, the above statement can only be regarded as a hypothesis, and more evidence needs to be confirmed. However, for modern people who want to improve their health, there is no need to sort out the ins and outs behind it. Perhaps, just follow some practices that are backed up by human research(For example, intermittent fasting, short bursts of high-intensity exercise, etc., can review previous articles)to see the benefits.

In addition, we can also wait for the latest results from the scientific community. This year's American Chemical Society SpringAt the conference, researchers at Washington University in St. Louis found a compound that could mimic the effects of exercise on the human body. This undoubtedly provides a new way of thinking about health that uses drugs to simulate adversity. We also look forward to more similar drugs in the future, so that we can enjoy the same health benefits without having to experience uncomfortable feelings such as hunger and cold.