Sonali Bendre follows an 18 to 20-hour fast for autophagy: Here's what doctor says

Actor Sonali Bendre recently revealed that she follows intermittent fasting for around 18 to 20 hours, saying she does it to promote "autophagy," the body's natural process of cellular repair.

Her comments have sparked fresh interest in extended fasting, with many wondering whether skipping meals for long periods really unlocks significant health benefits.

While the idea sounds promising, experts say the science is more nuanced than social media trends often suggest.

Let's understand what autophagy is

Autophagy is the body's natural recycling system. It helps cells identify damaged proteins, worn-out cell parts and other unwanted

material, break them down and reuse their building blocks to maintain healthy cellular function.

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"Autophagy is the body's natural process for recycling cells. In this process, cells recognise damaged proteins, old organelles and other unneeded components, degrade them and recycle their building blocks to keep the cell healthy," explains Dr Sanjay Raina, Head of Internal Medicine at Amrita Hospital, Faridabad.

The importance of this process was recognised globally when Japanese cell biologist Yoshinori Ohsumi received the Nobel Prize in Physiology or Medicine in 2016 for his discoveries relating to autophagy.

According to Dr Raina, laboratory and animal studies suggest that autophagy may contribute to healthy ageing, immune regulation, metabolic health and protection against neurodegenerative diseases.

Does a 20-hour fast trigger autophagy?

This is where many misconceptions begin.

"Extended fasting is again in the spotlight as actor Sonali Bendre recently talked about intermittent fasting for 18 to 20 hours to get autophagy. Her discipline is admirable, but we need to be careful to differentiate between scientific evidence and popular wellness trends," says Dr Raina.

Many people believe that fasting for 20 hours automatically switches on beneficial levels of autophagy. However, Dr Raina says the current evidence simply does not support such a definitive claim.

"Currently, there is no robust human evidence that identifies a specific duration of fasting at which clinically meaningful autophagy begins."

He explains that much of what we know comes from animal and laboratory studies rather than large-scale human research.

"Autophagy levels depend on age, body composition, activity level, genetics, metabolic health and even what you ate before fasting."

In other words, there is no universal timer that guarantees autophagy after a set number of fasting hours.

So, is intermittent fasting still beneficial?

The answer is yes, but perhaps not for the reason many people think.

"Several clinical trials have shown benefits for body weight, insulin sensitivity, blood pressure, fatty liver disease and inflammatory markers in overweight people," says Dr Raina.

He adds that these improvements are not exclusive to very long fasting windows.

"Thankfully, these benefits aren't just limited to a 20-hour fast. Often, eating within an 8 to 10-hour window, cutting excess calories and eating a healthy diet leads to similar metabolic improvements."

This means that sustainable eating habits may provide many of the same health benefits without requiring extremely long fasting periods.

Is a 20-hour fast suitable for everyone?

Definitely not.

Dr Raina cautions that prolonged fasting can pose risks for certain groups and should only be attempted under medical supervision where appropriate.

"Prolonged fasting is not appropriate for some people."

He advises that people with diabetes who take glucose-lowering medication, pregnant or breastfeeding women, frail older adults, underweight individuals and anyone with a history of eating disorders should avoid extended fasting or seek medical advice before trying it.

"If you don't eat enough during extended fasting, you can develop hypoglycaemia, dehydration, muscle loss, fatigue and nutritional deficiencies."

For these individuals, the potential risks may outweigh any possible benefits.

What really matters for long-term health?

Although autophagy continues to be an exciting area of research, Dr Raina stresses that it should not be viewed as a shortcut to longevity.

"Autophagy is not an instant solution to longevity."

Instead, he points to lifestyle habits with far stronger scientific evidence.

"The most powerful evidence-based strategies for long-term health are regular exercise, restorative sleep, healthy weight, no tobacco use and a balanced diet rich in vegetables, fruits, whole grains, lean proteins and healthy fats."

The bottom line

Sonali Bendre's fasting routine has certainly reignited the conversation around autophagy, but experts urge people not to assume that longer fasting automatically translates into greater health benefits.

As Dr Raina concludes, "Some people can do a 20-hour fast under medical supervision but it's not for everyone. Good health still starts with sustainable lifestyle habits, not extreme fasting windows."

For now, the science suggests that while autophagy is a fascinating biological process, there is still much to learn about how fasting influences it in humans. Until stronger evidence emerges, consistency, balance and healthy everyday habits remain the most reliable path to better health.