Is intermittent fasting, which has been repeatedly "deified", a "code for renewal" or a "health trap"?

Produced by: Science Popularization China

Author: Flower Tea (Qingdao Agricultural University)

Producer: China Science Expo

Recently, a study has caused a stir in the field of health and wellness: intermittent fasting may cause hair loss . This undoubtedly poured cold water on the recently highly praised "intermittent fasting". You can keep your figure but lose your hair. It's a difficult decision to make.

What exactly is intermittent fasting, which has been repeatedly praised as a god? How should we view intermittent fasting scientifically?

New scientific discovery: potential link between intermittent fasting and hair loss

In this study, researchers followed a certain number of people who practiced intermittent fasting for a long time. They recorded in detail the participants' eating patterns, various physical indicators, and hair health. After several months of close monitoring, they found that the proportion of these people with hair loss problems was significantly higher than that of people with a normal diet.

On December 13, 2024, Zhang Bing's team from West Lake University published a paper in Cell

(Image source: Screenshot from Cell’s official website)

In order to explore the reasons behind this, the research team conducted an in-depth data analysis. They found that when the body is in a state of intermittent fasting, the intake of nutrients is greatly reduced. The normal growth of hair requires the support of multiple nutrients, such as protein, which is the main component of hair, iron, which is involved in the oxygen transport of hair follicle cells, zinc, which plays a key role in regulating the hair growth cycle, and B vitamins, which help maintain a healthy environment for the scalp.

During intermittent fasting, due to the restriction of food intake, these key nutrients are often difficult to meet the body's needs, which may affect the normal metabolism and function of hair follicle cells. Hair follicles may enter the resting phase due to lack of nutrition, resulting in increased telogen effluvium, while the growth of new hair becomes slow and sparse, eventually leading to hair loss problems, making the originally thick hair gradually become thin, fragile, and even fall out in large clumps. This undoubtedly rings the alarm bell for people who are keen on intermittent fasting.

Hair loss

(Photo source: Veer Gallery)

Intermittent fasting has always been regarded as a simple and effective way to manage health, but this study makes us re-examine its potential negative effects.

What exactly is intermittent fasting?

Intermittent fasting does not mean that you should not eat at all and starve . There are several common modes, such as the "5:2 intermittent fasting", which means that you eat normally for 5 days out of 7 days a week. During these 5 days, you can follow your daily eating habits to consume the calories and various nutrients needed to maintain the normal functioning of the body, and enjoy delicious food while maintaining physical vitality. On the other two non-consecutive days, the diet is restricted. The calorie intake of women on these two days is generally controlled at around 500 kcal, and that of men at around 600 kcal. This requires being more cautious in food selection, and choosing more low-calorie, high-nutrient-density foods, such as vegetables, fruits, chicken breast, fish and shrimp, etc., and avoiding high-calorie, high-fat, high-sugar foods, such as fried foods, cakes, beverages, etc.

Another method is "16:8 light fasting", which means fasting for 16 hours out of 24 hours a day, and eating only in the remaining 8 hours. During the fasting period, except for water, try to avoid consuming other food and drinks to give the stomach and intestines a full rest. During the 8 hours of eating, you can eat normally, but you should not overeat. You should still follow the principle of a balanced diet to ensure the intake of various nutrients.

Intermittent energy restriction diet

(Photo source: veer photo gallery)

The concept of intermittent fasting stems from people's exploration of the body's metabolic regulation mechanism. The principle behind it is that appropriate fasting time can allow the body to enter a "self-repair" mode. During the fasting period, the body will reduce insulin levels and start the cell autophagy process, which is like a big cleanup inside the body, removing some damaged cells and proteins, thereby promoting cell renewal and regeneration.

Intermittent fasting has many health benefits

There is a lot of evidence showing that intermittent fasting may have a positive impact on the body's metabolism, blood sugar regulation, and other aspects . Some studies have even found potential benefits for cardiovascular health and brain function , such as lowering blood cholesterol and triglyceride levels, reducing the body's inflammatory response, and enhancing the brain's cognitive ability and concentration.

From the perspective of weight loss, intermittent fasting does have a certain effect . When we reduce calorie intake, the body will begin to consume stored fat to provide energy, thereby helping to lose weight. Moreover, this way of weight loss is relatively mild, and is not as likely to cause strong resistance from the body as some extreme dieting methods, such as a sharp drop in metabolism, endocrine disorders and other problems. During the intermittent fasting process, the body will gradually adapt to the changes in this eating pattern, adjust the energy metabolism pathway, and make fat burning more efficient, so that while we enjoy delicious food, we can also slowly get rid of excess fat and shape a healthier body.

For blood sugar regulation, intermittent fasting can help improve insulin sensitivity . For some pre-diabetic patients or people with insulin resistance, intermittent fasting can make the body's cells more responsive to insulin, better regulate blood sugar levels, and reduce the risk of diabetes. After we eat, the body secretes insulin to help cells absorb glucose in the blood and convert it into energy or store it. However, a long-term high-calorie diet may cause cells to become less sensitive to insulin, greatly reducing the effectiveness of insulin and making blood sugar difficult to effectively control. Intermittent fasting can improve the body's ability to regulate blood sugar by reducing blood sugar fluctuations and making the secretion and action of insulin more stable, just like a "repair and upgrade" of the blood sugar metabolism system.

Intermittent fasting also has an inhibitory effect on the body's inflammatory response . In modern life, many chronic diseases are related to the body's chronic inflammatory state, such as cardiovascular disease, arthritis, etc. Intermittent fasting can reduce the production of inflammatory factors in the body and reduce the damage of inflammation to the body's tissues and organs. It is like pouring a basin of water on the body's inflammatory fire, allowing the body to be in a relatively healthy internal environment. When the body is in a fasting state, it will reduce the synthesis of some pro-inflammatory substances, while activating the body's internal anti-inflammatory mechanism and enhancing the immune system's anti-inflammatory ability, thereby helping to prevent and alleviate various chronic inflammatory diseases.

In addition, from a psychological perspective, intermittent fasting can cultivate our self-discipline and a correct attitude towards food. During the fasting process, learning to control appetite and overcoming excessive desire for food can enhance our sense of self-control, and make us cherish the food we eat during mealtimes, improve the quality of our diet, and avoid unnecessary snacks and high-calorie junk food. When we successfully complete an intermittent fasting plan, we will gain a sense of accomplishment, which will further motivate us to maintain self-discipline in other aspects of life, such as exercising regularly, keeping a regular schedule, etc., thus forming a virtuous circle and making our lives healthier and more orderly.

But intermittent fasting is not perfect and can also cause health problems

Intermittent fasting is not perfect. As we mentioned earlier, hair loss is just one of the possible adverse consequences. Due to insufficient nutrition intake, in addition to hair, the skin may become dry and dull, and nails may become brittle and easy to break. The body's immune system may also be affected, because the normal functioning of the immune system requires adequate nutritional support. Nutritional deficiencies can reduce the activity and number of immune cells such as white blood cells, resulting in weakened body resistance and greater susceptibility to viruses, bacteria and other pathogens, which may increase the frequency of illness.

Long-term intermittent fasting may also have adverse effects on the female reproductive system. Women of childbearing age may experience menstrual disorders, reduced menstrual flow, or even amenorrhea. This is because the body's nutritional reserves are insufficient and it is unable to maintain normal reproductive hormone levels and physiological cycles, affecting the quality of eggs and ovulation function, which in turn poses a potential threat to fertility. Women who are preparing for pregnancy may reduce the chance of conception if they perform inappropriate intermittent fasting, and may even have adverse effects on the early development of the fetus, increasing the risk of miscarriage and premature birth.

In terms of emotions, intermittent fasting may make some people irritable, anxious, depressed or inattentive. The brain needs enough glucose and nutrients to maintain normal neurotransmitter synthesis and nerve signal transmission. If the dietary intake is insufficient, the brain's "emotional regulation center" and "cognitive function area" will be affected, leading to mood swings and decreased cognitive ability, making it difficult for people to maintain a good state at work and in life. For example, when studying or working, problems such as memory loss, slow thinking, and difficulty concentrating may occur, affecting learning and work efficiency.

Intermittent fasting is not suitable for everyone . For example, children and adolescents are in a critical period of growth and development, and their body's nutritional needs are very high. Intermittent fasting may hinder their physical and brain development. At this stage, they need sufficient nutrients such as protein, carbohydrates, fat, vitamins and minerals to support bone growth, muscle development, and brain cell proliferation and differentiation. If intermittent fasting is performed, it may lead to problems such as slow height growth, no weight gain, and decreased learning ability.

Pregnant women and breastfeeding women need extra nutrition to meet the growth of the fetus and the secretion of milk. Intermittent fasting will affect the health of mother and baby . The growth and development of the fetus in the mother's body is completely dependent on the nutrients provided by the mother. If pregnant women practice intermittent fasting during pregnancy, it may cause malnutrition of the fetus and affect the organ development and intellectual development of the fetus. If breastfeeding women do not take in enough nutrition, it will not only affect the amount of milk secretion, but also reduce the quality of milk, affecting the healthy growth of the baby.

The elderly are already prone to malnutrition due to their declining physical functions and reduced ability to absorb nutrients. Intermittent fasting is undoubtedly a double whammy. The elderly are already inferior to young people in various physiological functions, their gastrointestinal digestion and absorption capacity is weakened, and their body reserve capacity is also reduced. Intermittent fasting may make their bodies weaker, their immunity further reduced, and increase the risk of falls, fractures, infections, etc., seriously affecting their quality of life and healthy life expectancy.

In addition, people with certain chronic diseases such as gastric ulcer, duodenal ulcer, malnutrition anemia, severe liver and kidney dysfunction, etc. are not suitable for intermittent fasting, otherwise it may aggravate the condition and even cause serious complications. For example, the gastric mucosa of patients with gastric ulcer and duodenal ulcer has been damaged, and regular diet and adequate nutrition are needed to promote the healing of ulcers. Intermittent fasting may cause abnormal gastric acid secretion, irritate the ulcer surface, aggravate pain and bleeding symptoms, and delay the healing process of ulcers.

How to treat intermittent fasting correctly?

For those who want to try intermittent fasting, here are some health tips to help you enjoy the possible benefits of intermittent fasting while minimizing its potential harms.

Before starting intermittent fasting, you must fully understand your physical condition. It is recommended to consult a doctor or a professional nutritionist first, conduct a comprehensive physical examination, and evaluate whether intermittent fasting is suitable for you and which intermittent fasting method is suitable for you. Especially for people with underlying diseases, taking medications, or who are in a weaker body, do not start rashly. The doctor can provide you with personalized advice by asking about your medical history in detail, testing physical indicators, etc., to ensure your health and safety.

If you have permission from your doctor or nutritionist, you should pay special attention to balanced nutrition intake during intermittent fasting. On eating days, you should ensure the diversity of food, including various nutrients such as grains, vegetables, fruits, proteins (such as lean meat, fish, beans, eggs, dairy products), healthy fats (such as olive oil, fish oil, nuts), etc., to ensure that the body gets enough vitamins, minerals and dietary fiber. For example, for breakfast, you can choose a serving of whole wheat bread, a glass of low-fat milk, a boiled egg and a serving of fresh fruit. For lunch and dinner, you can pair it with brown rice, various vegetables, and an appropriate amount of lean meat or fish to ensure that each meal is rich in nutrients. On fasting days, you can choose some low-calorie, high-nutrient-density foods, such as vegetable soup, sugar-free yogurt, fruit salad, boiled eggs, etc., to avoid nutritional deficiencies and physical discomfort caused by complete fasting.

In order to reduce the stress and nutritional loss of fasting on the body, some nutrients can be supplemented appropriately . For example, B vitamins are very important for maintaining the health of the nervous system and skin. They can be supplemented by eating whole wheat bread, oatmeal, lean meat, liver and other foods, or taking B vitamin supplements under the guidance of a doctor; protein is an important component of hair, skin, muscle and other tissues. On fasting days, you can choose protein powder or foods rich in high-quality protein to ensure adequate intake; iron is also indispensable for preventing anemia and maintaining hair health. You can eat more iron-rich foods such as red meat, beans, green leafy vegetables, or take iron supplements.

At the same time, pay attention to the body's signals. If you experience dizziness, palpitations, fatigue, nausea, menstrual disorders, severe hair loss and other discomfort symptoms during intermittent fasting, you should stop intermittent fasting immediately and seek medical attention in time. This may be an alarm sent by the body, indicating that intermittent fasting has caused excessive burden on the body and needs to adjust the diet and lifestyle. During the intermittent fasting period, pay attention to maintaining adequate water intake and drink at least 1500-2000 ml of water every day to help the body excrete metabolic waste and maintain normal physiological functions.

In addition to diet, adequate sleep and moderate exercise are also important components of a healthy life. Lack of sleep will affect the body's metabolism and hormone balance, weaken the body's self-repair ability, and even if you do light fasting, it is difficult to achieve the ideal health effect. It is recommended to ensure 7-8 hours of high-quality sleep every day, develop a regular schedule, try to go to bed before 11 o'clock in the evening, and get up around 7 o'clock in the morning to keep the body's biological clock stable. Moderate exercise can help improve the body's metabolic level, enhance muscle strength and cardiopulmonary function, and relieve stress and anxiety, but be careful to avoid excessively strenuous exercise during fasting to avoid physical exhaustion and accidents. You can choose some gentler exercise methods such as walking, yoga, and Tai Chi. The exercise time should not be too long, generally 30 minutes to 1 hour is appropriate.

Cherish your body

As a way of eating, intermittent fasting has its unique benefits, but also certain risks. We should not blindly follow the trend, but should understand and treat it with a scientific and rational attitude, and carefully choose whether to do intermittent fasting and how to do it according to our physical condition and life needs. Only in this way can we walk more steadily on the road to health, avoid falling into unnecessary health traps, and truly achieve health and vitality from the inside out.

After all, health is a long marathon, not a sprint. Every choice of diet and lifestyle should be a care and respect for the body, rather than excessive consumption and harm.