Sonali Bendre’s 18–20-hour intermittent fasting: Should you try it?

When actor Sonali Bendre recently spoke about following an 18–20-hour intermittent fasting routine and eating roughly one-and-a-half meals a day, it naturally attracted attention. Celebrity wellness routines often do. They sound disciplined, simple and tempting to copy. Eat less often, fast longer, and stay healthy — that is the message many people take away.

But the public conversation around intermittent fasting needs a little correction. Fasting may help some people, but it is not magic. For weight loss, calorie restriction remains central. That calorie restriction can be timed, as in intermittent fasting, or not timed, as in a conventional balanced diet with smaller portions. The eating clock can be useful, but the calorie deficit is what drives weight loss.

Intermittent fasting is an umbrella term

This includes time-restricted eating such as 14:10, 16:8 or 18:6 patterns, alternate-day fasting, and the popular 5:2 diet, where calorie intake is sharply reduced on two days of the week. These approaches differ in design, but the broad principle is similar: they reduce the opportunity to eat. For many people, this automatically cuts out late-night snacking, repeated cups of sweet tea, biscuits, namkeen, sugary drinks and mindless grazing.

That is why fasting often works. Not because the body suddenly ignores calories, but because the person eats fewer calories over the day or week. This distinction matters. Many people begin extreme fasting believing that longer fasting means faster fat loss. Some skip breakfast, delay lunch, survive on coffee, and then reach dinner excessively hungry. The result may be a large meal, sweet cravings, acid-peptic disease, headache, irritability, poor sleep and reduced physical activity. The fasting window may look impressive, but if the total calorie intake remains high, weight loss will be limited.

What studies say so far

A pooled analysis of 28 randomized trials studied time-restricted eating, alternate-day fasting and the 5:2 diet for periods ranging from 2 to 52 weeks. When the three intermittent fasting approaches were combined, they did not produce superior weight loss compared with continuous calorie restriction. The difference in body weight was small and not statistically significant. Fat mass reduction was also comparable. The analysis found small additional reductions in waist circumference and fat-free mass with intermittent fasting approaches, but no meaningful advantage for glucose, lipids or blood pressure. The authors concluded that intermittent energy restriction diets were not superior to continuous energy restriction for improving body composition and cardiometabolic risk markers.

This is the most important message: fasting is better than eating without structure, but it is not necessarily better than ordinary calorie restriction. If two people reduce calories to a similar extent, one through a fasting window and the other through smaller regular meals, their weight-loss outcomes may be similar. This should actually be reassuring. It means one does not have to follow an extreme 18–20 hour fast to lose weight. Some people may do well with time-restricted eating. Others may do better with three planned meals, better portions, fewer refined carbohydrates, adequate protein and no unnecessary snacks. Both approaches can work if they reduce calorie intake and can be sustained in the long run.

The problem with celeb diets

The problem with celebrity-inspired fasting is that it often ignores context. The celebrity may have a controlled routine, access to expert advice, planned meals, trainers, and years of body awareness. What works for that person may not suit a teacher leaving home early, a doctor on night duty, a person with diabetes, a woman around menopause, or an older adult with low muscle mass.

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Muscle is an important part of this discussion. After 40, and especially after 50, weight loss should not come at the cost of muscle loss. Muscle helps glucose control, balance, and mobility. If someone eats only one large meal or one-and-a-half meals a day, it may become difficult to get enough protein, fibre, calcium, iron, vitamin B12 and other nutrients unless the diet is carefully planned. Weight loss with muscle loss is not ideal weight loss.

This is especially relevant in India, where many people have central obesity with relatively low muscle mass. A person may not appear very overweight but may have abdominal fat, fatty liver, high triglycerides, prediabetes or diabetes. In such individuals, the aim is not simply to “eat less often.” The aim is to reduce excess calories, preserve muscle and improve metabolic health.

People with diabetes need additional caution. Long fasting windows can cause low glucose in those taking insulin or sulfonylurea tablets. Others may break the fast with a large carbohydrate-heavy meal, producing a sharp rise in post-meal glucose. People with diabetes, pregnancy, eating disorders, frailty, chronic kidney disease, active illness, or older adults at risk of muscle loss should not start extreme fasting without medical advice.

For most people, a less dramatic plan is more useful. Begin with a 12–14-hour overnight gap. Finish dinner early, avoid late-night snacking and eat the next morning at a regular time. This is also a form of time restriction, but it is easier to sustain. Then focus on what is being eaten: protein in every meal, vegetables, fibre, controlled portions of rice and roti, fewer fried foods, fewer sweets, and no sugary drinks. Add a 10–15-minute walk after meals and resistance exercise two to three times a week.

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So, should people try intermittent fasting? Yes, if it suits their body, medicines, work routine, sleep and mental health. But it should not become a competition over who can fast longer. An 18–20 hour fast may work for a disciplined individual with a carefully planned lifestyle. It is not necessary for everyone.

A meal plan succeeds only if it can survive real life. Many diets fail not because the science is wrong, but because the plan is too rigid. A person may follow an extreme fasting schedule for a few weeks, but if it causes constant hunger, social discomfort, poor sleep, low energy, or repeated overeating, it is unlikely to last. The best meal plan is not the one that looks most disciplined on paper; it is the one a person can follow on working days, weekends, travel days, family functions and festivals. It should allow familiar foods, affordable choices, adequate protein, vegetables, fibre and controlled portions, without making every meal feel like a test of willpower.

(Dr Bhattacharya is endocrinologist at Apollo Hospital, Delhi)