In 2003, Oprah announced she was no longer eating after 7.30pm to stave off weight gain. “Not even a grape,” she wrote in the January issue of O, The Oprah Magazine, where she meditated on her heaviest (237 pounds) and lightest (145 pounds) selves—and all the dietary tweaks and allowances and emotional ups and downs that led her there. And while this writer, like much of the world, takes everything Oprah says as fact, I never knew why not eating late made sense, instead figuring it simply allotted for less time to burn off calories. Turns out, not only does our body burn fat and our brain reset in the middle of the night, but every organ cleanses itself, too. That is, if our internal 24-hour clock—known as the body’s circadian rhythm, or internal daily time table—is programmed properly to get the job done.
To get your body on track, professor Satchin Panda, a leading expert in circadian rhythms research and the author of The Circadian Code, believes in maintaining an eight- to 10-hour eating window, which allows for a minimum 14-hour overnight cleanse.
“If you look around at anything that moves in our daily life, they all revolve around timing,” says Panda, who often cites the rise and fall of the sun as a good, foolproof example. “And yet, we schedule every [meal] in our life around school, work, appointments, phone calls.” This pattern of eating, which for the average American lasts over 15 hours and can go well past dark, when the brain should release melatonin in preparation for sleep, is directly at odds with our biological clocks, he says. “For so long, we often only heard about what and how much or what type of medications to take,” he continues. Instead, Panda believes the answers may lie in “the biology of time, and how our body remembers time.”
It’s a thrilling thought: The best lifestyle may not have to do exclusively with what you eat, but when you eat. And Panda’s interests have led to a growing number of studies and experiments that suggest many diseases plaguing the modern world, from obesity and diabetes to depression and anxiety to various types of cancer, even dementia, are caused by a breakdown in circadian rhythms, he says. Perhaps even more fascinating? “We know diseases get worse when people endure [night] shift work, which leads to circadian disruption,” Panda says, “but I was really surprised by the range of diseases that reversed—and in two to three months’ time.”
Here, Panda and nutritionist Amy Shapiro, M.S., R.D., the founder of Real Nutrition NYC, discuss the benefits (better sleep and weight loss are just the tip of the iceberg) and everything you need to know about time-restricted eating, or intermittent fasting, so you can successfully get your circadian rhythm back on track. The bottom line? Oprah was right.
Take Stock of Your Daily Routine
Let’s face it, eating within an 8-hour window such as 9am to 5pm sounds near impossible—especially if you have children, or live in a bustling city, or have a job that requires shift work, or simply consider yourself “an average person who just doesn’t like to feel hungry,” says Shapiro. Everyone faces different challenges in his or her schedule, which is why experts simply want you to start off by being mindful about when you are eating. “It takes only two nights of late eating or abusing sleep by less than five hours to cause this disruption,” says Panda. His team at the Salk Institute for Biological Studies recommends starting with a 12-hour window of eating and working your way up to the optimal eight-hour time frame, when endurance, weight loss, and prediabetic reversal can happen in two months. “I call it the magic time,” he says of the duration that may also lead to the end of panic attacks, premenopausal migraines, and period pain, as well as other flare-ups from predisposed diseases.
Start With This Simple Morning Tweak
A 14- to 16-hour “cleanse” period of not eating between dinner and breakfast can sound like a stretch for most people, but according to Shapiro, much of it comes down to perception. “After two to three weeks, you’ll realize that a lot of what your body wants is simply out of habit,” she says, much, like, say, brushing your teeth twice a day. Small tweaks to your normal routine can make a big difference. For instance, consider bringing your breakfast to work, says Panda, instead of eating the minute you wake up. At night, share dinner with your family as usual. It’s worth noting, he continues, that “people who stop at 6pm or 7pm at night are less likely to indulge in dessert, and will therefore see the biggest difference [in health and weight loss].”
Give Yourself a Week to Adjust
The first week is going to be difficult, says Panda. “You will feel hungry, but it’s a healthy hunger.” After three to four hours of not eating, when the body is depleted of sugar, it is ready to tap into the carbohydrates that get stored in your liver, which is actually a good thing, says Panda. “It’s like having a house full of stuff,” he says. “Unless you get rid of it, you shouldn’t go shopping.” Overnight fasting is a different story: By morning, in the last four hours of our fast, we are literally burning fat. “And that fat is converted to ketone bodies, which is going to fuel our brain and heart,” says Panda. Ever tried those expensive hydroxybutyrate supplements that promote fat-burning and mental clarity? “Your body is producing 50 to 100 grams of the same stuff you’re buying,” says Panda. “But for free.”
In two to three weeks’ time, the body will readjust, the positive side effects will kick in, and you will likely find yourself effortlessly passing on after-hours offerings, continues Panda. But, he is quick and firm to point out this isn’t about skipping meals. And Shapiro agrees: “It is not about not eating, or cutting calories; it’s about closing the window so you’re not eating during the time when you actually don’t need fuel,” she says. “None of my healthy clients have ever felt shaky from low blood sugar—in fact, the people who do commit to it, feel more energized.”
A Hearty Breakfast—And Less Processed Foods—Help
“Everyone is afraid to be hungry, and that’s exactly why diets fail,” says Shapiro. “But if you eat the right foods, you don’t feel that type of uncomfortable, angry hangry kind of hunger.” Whether you’re eating in or taking a meal to go, Panda suggests making a hearty breakfast. “You’ll find you don’t eat too much after a meal rich in protein or fat, because they’re both very filling.” Think two eggs and half of an avocado instead of a bagel: “If you’re going to get all your nutrients in, your meals need to be balanced.” Fiber, protein, and a good healthy fat are safe—and will likely nourish you for a good few hours. Then, eat a light lunch before dinner, which should consist of protein, fat, and a healthy carbohydrate like whole-grain bread, which will help you go into your 14-hour marathon fast. “We humans love to have a good dinner with our loved ones; even in preindustrial era, when we were hunters and gatherers, we would bring whatever we caught in the day and light up a fire and bake or roast it and share it amongst family and friends.” And when would that happen? Just before nightfall.
This Rhythm Works for Exercising, Too
Workout enthusiasts won’t be surprised to hear that different times of the day also come with specific benefits. If you’re in need of a mood lift, exercising outside or by a large window in the morning time is your strongest natural antidepressant. “It’s free and plentiful,” says Panda. “Also, morning cortisol is good for increasing alertness.” And if you’re hoping to give up that midday jolt of caffeine, consider scheduling a gym visit. That tired feeling is caused by “stress and deadlines, because we forget to breathe,” says Panda. “A midday workout will bring back oxygen into the body—and give you a very healthy hunger before lunch.” But perhaps most telling? “We are designed to exercise optimally in the evening,” says Panda, who cites our ancestors again, and their run home from working in the fields, before the sun would fall. That’s why, for better muscle tone and joint flexibility, exercising between 5pm and 7pm is best, says Panda.
With Good Sleep Comes Better Gut Health—And Glowing Skin
During deep sleep associated with this 14-hour cleansing window, the brain produces a growth hormone that is meant to repair both the gut lining and the skin lining. In fact, says Panda, “every 10 to 15 days, we should have a completely new layer of skin.” And in order for this to best work, you need to allow the body to fully repair itself. “Just like you can’t repair a highway when the traffic is flowing,” starts Panda, “you can’t eat two to three hours before bedtime.” There will be less holes in both the gut and skin linings for chemicals or bacteria to seep in which in turn, continues Panda, will improve our immunity by presenting a more healthy barrier and preventing viruses from entering the body. All in all, it’s a small price to pay for a healthier, happier life.
This article first appeared on Vogue.com