Watch when you eat: Restricting the time over which you eat may help lose weight

There’s no easy recipe for weight loss, but scientists have now devised a simple plan that gets results without menu makeovers and without overhauling your daily activity schedule. When you eat is as important as what and how much you eat. A growing body of research shows that eating within an eight to 10 hour window leads to weight loss without changes in food or activity levels. The basic rule is to be in bed for eight hours (not necessarily asleep for eight hours), and to eat all food and calories within an eight to 10 hour window (say, from noon to 8pm).

That’s the golden new advice from Dr Satchidananda Panda, author of ‘The Circadian Code’. A professor of regulatory biology laboratory at the Salk Institute for Biological Studies in San Diego, California, Dr Panda’s work with mice started the whole intermittent fasting craze that shows no signs of dying down.

While exploring the liver’s sleep-wake cycle, Dr Panda discovered that mice who ate within a set eight to 12 hour period were slimmer and healthier than those who ate the same amount of calories over a longer period of time.

“Although (in mice) the benefits are better at eight hours than 10 hours or 12 hours, 10 hours is a relatively better time window to adopt. Eating within 12 hours may or may not benefit many people,” says Dr Panda, who explores the genes, molecules and cells that regulate the body’s circadian clock, that is, the body’s 24-hour sleep-wake cycle that controls our daily cycle of activities, like waking, sleeping, and releasing enzymes and hormones for digestion.

When this internal clock is disrupted – for example, when people eat erratically or do shift work – the balance between nutrition and rejuvenation breaks down, accelerating metabolic and degenerative diseases, including ageing. “Eating within eight to 10 hours is optimal for our circadian rhythm,” says Dr Panda.

He and his team followed up their work with mice with eight overweight persons, who typically ate during a period of 14 hours or more a day. When they switched to eating within a self-selected window of 10-12 hours seven days a week, they lost weight, slept better and had more energy in 16 weeks (less than four months). Apart from restricting the time between their first and last meals, they made no changes to their diet.

How to start

  • Choose a fasting method that fits your daily schedule.
  • Since you fast naturally overnight while sleeping, skipping or delaying breakfast is the easiest way to start.
  • Stop snacking completely.
  • Start by skipping one meal, either breakfast or dinner, and follow a 14/10 plan (fasting hours/eating hours), where the time between your first and last meal doesn’t exceed 10 hours.
  • Once you get used to two meals a day, then graduate to the 16/8 plan (fasting/eating).
  • Eat healthy fats, protein and veggies to lower cravings and sudden drops in blood sugar.

how it helps

  • Fewer cravings
  • Higher energy
  • Fat loss
  • Higher muscle mass
  • Improved insulin sensitivity and blood sugar control
  • Lowers inflammation
  • Increases good bacteria in the gut
  • Protects against liver disease and metabolic illnesses, like hypertension and diabetes
  • Exercising – resistance training for muscle gain – at the fag end of the fasting period increases benefits

other intermittent fasting methods16/8 Method

  • Fast for 16 hours, eat in an eight-hour window.
  • Flexi-plan, eat when you want as long as the gap between the first and last meal is eight hours.
  • The Leangains version of this plan – based on Martin Berkhan’s book, The Leangains Method, The Art of Getting Ripped – says men should fast for 16 hours, and women for 14 hours.


  • First meal by 6am, last meal by 5-6pm every day, no food after that.
  • Effective fasting lasts for 12-13 hours.
  • No food-group or calories restriction.

The 5/2 diet

  • Eat normally for five days and fast for two.
  • Just have water or restrict calories to 500 calorie (25% of calorie needs) for two days each week.
  • Choose from either one 48-hour fast or two non-consecutive 24-hour fasts.

Alternate-day fasting

  • Fast on alternate days, fasting on one day and eating normally the next.
  • Begin by fasting for 24 hours one or two times weekly.
  • Then graduate to every other day.
  • Option of having 500 calories (25% of calorific intake) on fasting days.

Eat-stop-eat diet

  • No food for 24 hours at a time, fasting from breakfast to breakfast.
  • Have water and other calorie-free drinks, like black coffee or herbal tea.
  • Return to normal eating patterns on the non-fasting days.

Warrior diet

  • Starve for 20 hours every day and eat one huge meal at night.
  • Some raw fruit and veggies allowed while fasting.
  • Eat the last meal a few hours before bedtime so it doesn’t interfere with sleep.

This was the first paper to show that eating within a 10-hour window can reduce weight among overweight adults, but since then, additional scientific papers have reiterated the outcomes – weight loss, improved insulin sensitivity, better sleep and reduced hunger – without increase in physical activity.

This “intermittent fasting” plan is a major departure from the accepted nutritional wisdom of eating small, frequent meals to prevent spikes in insulin levels. It is a fasting-feasting plan that ensures the body has a long enough resting phase for cell repair and rejuvenation.

Most people eat mindlessly through the day, starting with morning tea or coffee, and ending the day after three meals and several snack breaks, which often go on till late at night. This pattern of eating disrupts the body’s biological rhythms and raises the risk of diabetes, obesity, fatty liver, heart disease and stroke.

Eating behaviours are similar across continents. A study that looked at eating patterns in adults in the US found that they eat during a period of at least 15 hours or longer, with only 10 per cent consistently eating within a 12-hour window. Eating behaviour in India is very similar, with people eating over extended periods.

The only difference is that Americans start their meals later on weekends, unlike in India where eating patterns remain similar all days of the week.

Carbohydrates, particularly sugars and refined grains like white bread, maida and polished rice, are quickly broken down into glucose for cells to use as energy and the excess carbs are stored as fat by the insulin hormone. “Fasting triggers weight loss because the body enters the state of ketosis. When you cut back on calories for a sustained period, the body starts converting fatty acids into ketones, which are burned for energy, leading to weight loss. Only healthy people, however, must attempt prolonged fasting, as ketosis can be potentially life-threatening for people with uncontrolled diabetes and other chronic conditions,” says Dr Parmit Kaur, chief dietician, All India Institute of Medical Sciences (AIIMS).

People on medication for diabetes, kidney disease and liver disease, pregnant and lactating women, and children under 18 should not attempt intermittent fasting.

Stopping mindless eating and snacking in between meals is the key, but weight loss and health benefits get magnified if the meals are largely healthy.

“You don’t need to exclude any food group, but having a balanced meal, which includes eating more fruits, veggies, beans, lentils, whole grains, lean proteins, and healthy fats, and less of sugar, refined grains and processed foods, will amplify benefits,” says Dr Parmit Kaur.

People on extreme fasting plans, such as alternate-day fasting, are more likely to abandon it after a few weeks compared to people on a low-calorie plan,found a clinical trial of 100 healthy obese adults.

Manish Goel, 47, zeroed in on time-restricted eating while looking for a fuss-free diet to lose weight and beat fatigue. He chose the 16:8 plan where he fasts for 16 hours and eats between eight hours every day. Goel only has “zero calorie” drinks including warm lemonade without sugar, coffee and apple cider vinegar before he has his first meal at around 2pm and the last by 10pm.

Goel has lost 5.2 kg and his belt buckle is tighter two notches since January 2 this year, when he started the plan on the recommendation of his trainer Vishal Kumar and a very fit friend in Malaysia, Susan Key, who follows it with great results.

“I work 10 to 12 hours a day on sustainable energy solutions, which prompted me to look for a sustainable nutrition plan, where I didn’t have to count calories and spend too much time planning meals,” says Goel, founder and chief technology officer, ICube Nanotec India.

He has made absolutely no changes to his diet and eats regular food, including rice. “I don’t feel deprived at all. I have survived weekend parties and a big family wedding without a problem. I can’t believe I’ve lasted this long,” says Goel.

Though time-restricted eating does not require a major change in the quality or quantity of food, reducing the eating duration does lead to a fall in the overall caloric intake.

Goel initially missed food on Sunday mornings when he wasn’t working and was home with easy access to the fridge, but that stopped after the first few weeks of his beginning the 16/8 intermittent plan. “The only thing I’ve had outside the eating window a few times is a glass or two of red wine, but I have no cravings for food. In fact, I thought I would feel famished after my morning workouts that I do four days a week, but I don’t feel tired. I feel completely normal, which really surprised me,” he says.

Energy levels do go up, simply because the body is primed to convert food to energy at a fixed time and energy is not dissipated in digesting food through the day. “The basic rule to maintaining a healthy circadian rhythm (and preventing diabetes, obesity, heart and liver diseases etc) is stay in bed for eight hours, avoid calories for at least an hour after waking up, eat all food and calories within an eight to 10 hour window, and never eat beyond 12 hours,” says Dr Panda.

For better results, avoid bright light and food for two to three hours before going to bed. Also, step outside to get some daylight (though not necessarily sunlight) for 30 minutes every day. This will ensure the biological clock and all the hormones and enzymes that guard you against disease work the way they should.

Success Story: Akash Sehrawat shares how ‘intermittent fasting’ helped him

Personal trainer and yoga instructor Akash Sehrawat, 35, follows the 16/8 (fasting eating) plan, where he eats from 11 am to 7 pm, and fasts from 7 pm to 11 am the next day.

“I’ve been on it since 2013 and it has definitely worked for me. That’s the reason why I have been very consistent with it for over half a decade now,” he says.

He sought out the plan after reading former Israeli Special Forces member Ori Hofmekler’s bestselling The Warrior Diet (fasting for 20 hours, feasting for 4), but chose Martin Berkhan’s Leangains Method (16/8 fasting/eating) to, as the book’s title suggests, get ripped without starving through the day.

Sehrawat was not overweight when he started but chose a fasting plan to trim lose his belly fat and gain muscle mass. “Intermittent fasting, along with some improvements in exercise protocols, drastically improved my workout results,’ he says.

The unexpected bonus was looking forward to mealtimes. “I wanted a way out of eating five-seven small meals a day because I was fed up of eating that way. I wanted meals to be more enjoyable. This plan has reduced my meal frequency from five to seven smaller meals to two big meals a day, and helped me save a lot of time and effort in planning and cooking,” he says.

Like most people on a new diet, Sehrawat initially experienced food cravings because he was used to eating small meals every two hours. “Yes, there were cravings (but not hunger), but my body adapted pretty quickly, and within a few weeks, all the cravings subsided,” he says.

To combat cravings, he chose to have some healthy zero calorie beverages, such as organic black coffee, apple cider vinegar and matcha tea to keep going until 11am, when his fast ended and he had his first meal of the day.

“Genetically, we are designed to be in the fed and fasted state almost equally, but an overabundance of food has resulted in our being in a fed state most of the time, which has led to many health problems like diabetes and hypertension,” says Sehrawat, who is also a American Alternative Medical Association-certified holistic health practitioner.

What also drew Sehrawat to fasting was his belief that it was the natural way to eat. “Most cultures and religions – Hindus, Muslims, Christians, Jews, Jains, among others – observe some form of fasting, so there was enough evidence of the benefits of fasting for me to give it a try,” he says.

“Anyone who wants to give intermittent-fasting a try should start gradually. In my experience, the most practical of all plans is Martin Berkhan’s The Leangains Method, where you fast for 16 hours (men) and 14 hours (women) over any given 24 hours!” he says.

How Indians Eat: The Daily Pattern Of Eating For Indians Is Completely Out Of Whack

In a finding that busted the myth that most people eat three meals a day punctuated with a couple of tea, coffee breaks or snack breaks, a study of eating behaviours among Indians found that most people spend most of their waking hours eating and drinking stuff other than water.

People on average eat for 15.53 hours in a 24 hour day, found a Delhi University study that tracked what and when people ate using a simple camera phone. It found that the median breakfast time in India is 6:58 am (between 6:10 am and 7:27 am) and the last meal of the day, which includes snacks, is at 10:45 pm (10:18 pm± 11:58 pm), according to a 2017 study published in the journal PLOS One.

Dinner is the biggest meal in most homes, with people on average consuming 32.2% of their daily intake between 7 pm and 11 pm. Eating behaviours in India are comparable to people in the US, where most people ate frequently and erratically in their waking hours and fasted overnight while they were asleep.

Eating over an extended period does not give the metabolic system any time to rejuvenate.

“Humans are organisms with a 12-hour sleep-wake cycle, born to work for 12 hours and to get restorative sleep after sundown, when the basal metabolic rate falls and the body and mind rejuvenate. Modern lifestyle and conveniences like electricity and easy access to readymade food have increased the amount and the period over which we eat,” said lead author Neelu Jain Gupta, an associate professor of zoology at Chaudhary Charan Singh University, Meerut.

The basal metabolic rate is the amount of energy per unit time that the body needs to keep functioning at rest.

“Eating for more than 10 hours a day stresses the liver. Even two hours after a meal, the liver is still busy making enzymes and eating over extended periods doesn’t give it time to rejuvenate. If I am eating for 15 hours, my liver will work at least 17-18 hours a day,” said Gupta.

For the study, Gupta, who was then at the Department of Zoology, University of Delhi, asked volunteers to use a simple camera phone to photograph everything they ate and drank over21 days. “People in India, like in many developing countries, eat a diverse range of freshly-cooked food without standardised recipes, which makes it difficult to determine nutrition values. We used an image-based data collection system to overcome the barrier to food data collection, which typically requires matching food data to a standard library to assess portion size,” said Gupta.

While reminders to photograph everything they ate of drank were randomly sent to all volunteers, they were not asked to make any changes to their diet. Though they could potentially review collected data, it had no effect on their weight, suggesting that people do not realise on their own that their eating patterns are unhealthy.

First Published:
Mar 30, 2019 19:44 IST

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