Fast for two days a week, is the 5:2 fasting method the “savior” for “fatty liver”?

gossip

"If you go hungry for two days a week, your fatty liver will be cured."

There is a recent claim that the development of fatty liver disease can be prevented by the "5:2 fasting method" (that is, eating regularly 5 days a week and eating less or fasting on the other 2 days).

Rumor Analysis

This statement is debatable.

The study mentioned in the rumor comes from an animal experiment conducted by researchers from the German Cancer Research Center and the University of Tübingen. However, this study is only an animal study and is far from the human body. From the current research, intermittent fasting cannot treat or prevent fatty liver.

Data from the "Guidelines for the Prevention and Treatment of Fatty Liver Disease in China" show that the incidence of fatty liver disease in my country has increased year by year in recent years, with the prevalence of fatty liver disease in adults reaching 12.5% ​​to 35.4%, which means that one in three people suffers from fatty liver disease. Fatty liver disease has also surpassed viral hepatitis such as hepatitis B to become the world's number one liver disease.

Recently, it is said that "fasting for two days a week can cure fatty liver disease". Is this true?

It all started with a German study

The research mentioned in the statement "Fatty liver can be cured by fasting for two days a week" comes from an animal experiment conducted by researchers from the German Cancer Research Center and the University of Tübingen.

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The researchers first fed mice a Western diet (WD) rich in fat and sugar (fructose and sucrose) for 32 weeks to induce non-alcoholic steatohepatitis (NASH). (That is, normal mice were first fed a lot of sugar and fat to develop fatty liver.)

Then, the mice with fatty liver were divided into two groups. One group began to use intermittent fasting (5:2 light fasting mode) - fasting for 2 non-consecutive days a week. During the fasting period, the mice could not get food but had free access to water. Each fasting cycle started at 7 pm and lasted for 24 hours. The other group was in a non-fasting mode and could eat as much as they wanted.

The results showed that under the Western diet, the weight of the control group mice increased significantly, and the accumulation of epididymal and inguinal white adipose tissue increased significantly. The mice that adopted the 5:2 eating pattern were not so fat, and the levels of liver damage markers in the serum were significantly reduced, which alleviated the liver pathology. In addition, compared with the free-feeding control group, the 5:2 intermittent fasting also improved liver fatty degeneration, swelling caused by degeneration, inflammation, and even liver fibrosis.

Therefore, these researchers concluded that the 5:2 diet not only alleviates diet-induced obesity and metabolic dysfunction, but also slows the development of fatty liver disease.

“5:2 Light fasting”,

Can it really solve fatty liver disease?

First of all, this study is only an animal study and there is still a big gap between it and the human body.

Secondly, based on current research, intermittent fasting cannot treat or prevent fatty liver.

Fatty liver is a disease caused by excessive accumulation of fat in liver cells due to various reasons. Normally, fat in the liver accounts for 3% to 4% of the liver weight. If the fat content in the liver exceeds 5%, it is mild fatty liver, more than 10% is moderate fatty liver, and more than 25% is severe fatty liver.

According to the different causes, fatty liver mainly includes alcoholic fatty liver and non-alcoholic fatty liver. Alcoholic fatty liver, as the name implies, is a disease of abnormal liver cell structure or functional disorder caused by long-term excessive drinking. Non-alcoholic fatty liver disease (NAFLD), also known as metabolic dysfunction-associated fatty liver disease (MAFLD), is a common chronic liver disease that is related to genetic factors, metabolic abnormalities and bad living habits, such as obesity, metabolic disorders, diabetes, etc.

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The occurrence of fatty liver is closely related to diabetes and obesity. Data show that 60% to 80% of type 2 diabetes patients also suffer from fatty liver, and more than 80% of obese patients also suffer from fatty liver.

In 2023, a meta-analysis was conducted on the effects of intermittent fasting (IF) and nonalcoholic fatty liver disease (NAFLD), including a systematic review of 14 studies and a meta-analysis of 10 studies (a total of 840 participants, 44.64% were male). The fasting time lasted for 4 to 52 weeks. The types of fasting included 5:2 diet, modern alternate-day fasting, time-restricted eating or religious fasting. The results showed that there was only very limited and moderate-quality evidence that intermittent fasting may be useful.

In general, there is currently insufficient evidence to show that intermittent fasting can treat or prevent fatty liver.

What should we do to prevent fatty liver ?

Fatty liver is related to genetic factors, metabolic abnormalities and bad living habits. Fatty liver caused by genetic and metabolic abnormalities is almost impossible to prevent. We can only prevent fatty liver caused by bad living habits.

There are several ways to start:

Limit alcohol intake

Alcohol increases the risk of fatty liver. It is recommended to avoid alcohol intake as much as possible, try not to drink alcohol, and if you have to drink, drink as little as possible.

Weight Management

The main symptom of fatty liver is excess fat. And fat is directly related to obesity. Obesity is an important risk factor for fatty liver. Therefore, to prevent fatty liver, the most important thing is to avoid being overweight or obese. Therefore, you should pay attention to controlling energy balance, maintaining your weight within a healthy and reasonable range, and try to keep your body mass index (BMI) between 18 and 24.

Eat a balanced diet

An important way to maintain energy balance is to eat a balanced diet, try to achieve dietary energy balance, and avoid obesity caused by excessive energy intake.

In normal times, you should pay attention to limiting your total daily calorie intake and don't overeat; avoid high-oil, high-sugar, high-salt, and high-calorie foods to ensure the intake of high-quality protein; eat more whole grains, coarse grains, and vegetables to increase fiber and vitamins, and reduce the intake of high-fat and high-cholesterol foods, such as eating less fried chicken, less fatty meat, less beef hot pot, and less lard; avoid drinking alcohol, and drink less high-sugar beverages, milk tea, etc.

Exercise regularly

Increase physical activity and appropriately strengthen aerobic exercise 4-5 times a week, each time for more than 30 minutes, such as swimming, jogging, cycling, playing badminton, kicking shuttlecock, playing football, dancing, doing radio gymnastics, skipping rope, etc., can also promote the consumption of body fat, reduce weight, and help maintain a healthy weight.

It should be noted that mild fatty liver usually does not require treatment and can be reversed mainly by actively losing weight and improving eating habits. However, for moderate to severe fatty liver, it is recommended to take appropriate professional treatment , otherwise it may also progress to hepatitis, liver fibrosis and cirrhosis. Therefore, if it is moderate to severe fatty liver, everyone must follow the doctor's advice for treatment.

Looking in the mirror of rumors

The use of animal models is a common practice in nutritional science research because they can provide an initial understanding of human physiological and pathological processes. However, there are significant physiological, metabolic and genetic differences between animals and humans, and these differences mean that the results of animal experiments cannot be directly or simply extrapolated to humans.

References

[1]Gallage S, et al. A 5:2 intermittent fasting regimen ameliorates NASH and fibrosis and blunts HCC development via hepatic PPARα and PCK1. Cell Metab. 2024 May 2:S1550-4131(24)00135-9. doi: 10.1016/j.cmet.2024.04.015. Epub ahead of print. PMID: 38718791.

[2] Liu Aoxue, Zhou Xianghai, Zhang Xiuying, et al. Study on risk factors of non-alcoholic fatty liver disease[J]. Chinese Journal of Clinicians, 2021, 49(02): 165-169.

[3] Fatty Liver and Alcoholic Liver Disease Group of the Chinese Medical Association Hepatology Branch. Guidelines for the diagnosis and treatment of non-alcoholic fatty liver disease[J]. Chinese Journal of Diabetes, 2010, 2(1): 15-19.

[4] Hu Piao, Kong Dongming, Zhu Zhongxin. Analysis of the disease burden of non-alcoholic fatty liver disease in the Chinese population from 1990 to 2019[J]. Chinese Journal of Preventive Medicine, 2022, 23(04): 260-264. DOI: 10.16506/j.1009-6639.2022.04.004.

[5]DOI:10.3760/cma.j.issn.1674-5809.2010.01.006

[6] Intermittent fasting protects against liver inflammation and liver cancer. Retrieved May 8, 2024 from https://www.eurekalert.org/news-releases/1043801

[7]Younossi ZM, Zelber-Sagi S, Henry L, et al. Lifestyle interventions in nonalcoholic fatty liver disease. Nat Rev Gastroenterol Hepatol. 2023 Jul 4. doi: 10.1038/s41575-023-00800-4.

[8]Zhou PMC10198034.

[9] “Guidelines for the prevention and treatment of fatty liver disease in China”

Planning and production

Author: Ruan Guangfeng, Deputy Director of Kexin Food and Health Information Exchange Center

Review丨Zhang Yu, researcher/PhD, Chinese Center for Disease Control and Prevention, national health science expert