Fasting-induced autophagy does not guarantee illness reversal

A viral post on TikTok claims, "AFTER 24 HOURS OF NO FOOD, YOUR BODY SWITCHES TO AUTOPHAGY MODE. YOUR BODY STARTS SCAVENGING ITSELF. WHAT DOES IT EAT FIRST? TOXINS, FAT, CRYSTAL DEPOSITS, LUMPS, CYSTS, GARBAGE. Fasting is the quickest way you can heal your body and reverse illness."

A similar video with slightly different text at the bottom claiming animals use fasting to heal themselves has received over two million views and over 41,000 likes on TikTok. This claim has been circulating on TikTok for over a year with tens of thousands of user engagements. Archived posts can be found here, here, and here. 

Autophagy is a natural process within the body by which cells are broken down and reused to create new cells. Some studies show it can be triggered by fasting for 24-48 hours, which deprives the body of a new source of nutrients and so uses existing cells to create new ones.

However, the claims made in these videos are not accurate, and triggering fasting-induced autophagy is not safe for everyone.

In fact

While autophagy is a natural process, there are risks associated with fasting and fasting-induced autophagy. According to Harvard Medical School, fasting can cause "headaches, lethargy, crankiness, and constipation," lead to overeating, affect metabolism negatively, and cause older adults to lose too much weight.

A study published by the United States National Library of Medicine found that while autophagy can be beneficial, excessive autophagy may kill cells in the heart and has been linked to some heart problems.

The Cleveland Clinic states that not enough research has been collected on the length of fasting required to trigger human autophagy or on autophagy as a wellness strategy. “Depending on your health, fasting, reducing your calories, making drastic changes to your diet, or taking on a rigorous exercise routine may be dangerous,” the article says.

Medical News Today also notes that most studies on autophagy have not been carried out on humans, and that there is evidence that it has both beneficial and adverse effects, stating, “Anybody who is seriously considering making changes to their lifestyle to induce autophagy should, therefore, seek advice from a doctor beforehand.”

What do nutritionists have to say?

Dr. Priyanka Rohatgi, Chief Clinical Nutritionist at Apollo Hospitals in Bengaluru, told Logically Facts that "intermittent fasting induces autophagy when done as a pattern.” However, she says that while “few start feeling lighter, others start experiencing unusual anxiety, headaches, nausea, or other symptoms." Dr. Rohatgi said that the essentials of intermittent fasting are sticking to healthy choices in the eating window, good hydration in the fasting period, adequate exercise to prevent muscle loss, sufficient sleep, and good protein and fiber intake. She advises taking up intermittent fasting is not advisable for everyone, and that it is "not a good idea for kids below 18, pregnant and nursing mothers, type-1 diabetics, patients on chemo and radiation for cancer, individuals with eating disorders, or those suffering from migraine."

When asked whether fasting and autophagy could help heal one's body from any illnesses, Dr. Rohatgi said that it can  reduce inflammation and may ease conditions such as obesity, diabetes, and hypertension. However, she added that "people must seek medical advice before starting and run some blood work."

Nutritionist Amita Gadre told Logically Facts that an intense autophagy mode cannot be induced in one session of 24 hours. Intermittent fasting for standard periods like 8 or 16 hours may result in more autophagy happening, better nutrient absorption, or CRP levels going down (an indication of inflammation). However, a blanket recommendation such as the viral claim cannot be made because not everybody reacts to it the same way.

According to Gadre, the body does not start scavenging itself for nutrients during autophagy, but it starts being more efficient with the recycling process that already exists. She added that there is no research to correlate autophagy with fat loss because, by default, consuming less food creates a calorie deficit, and the body loses fat. Speaking about cysts and lumps, she added that autophagy cannot be recommended as a way to fight cancers because proper nutrition is essential for withstanding chemotherapy, radiation therapy, and other treatments. Gadre adds that what is eaten during non-fasting windows is as important as fasting when it comes to controlling illnesses.

The verdict

Medical professionals recommend that people should consult a doctor before attempting any dietary changes, including fasting to induce autophagy. Without precautions, detailed information, and consideration of pre-existing conditions and medications, the claim that continuously fasting for 24 hours could heal the body or reverse illnesses is misleading.