Changing When You Eat and Sleep Can Shrink Your Waistline
Scientist Satchin Panda, Author of The Circadian Code, says it’ll also improve your mood, your health, and your sleep
Biologist Satchin Panda, PhD, who has studied the ins and outs of the body’s internal rhythms for more than 20 years, calls a disrupted circadian clock “the mother of all maladies,” and claims that making simple changes in the timing of when we sleep or eat can have a profound impact on our health — not to mention our waistlines. In fact, his book The Circadian Code, out in paperback this month, has a whole cadre of devoted readers — including this one — focused on restoring their natural biologic rhythms by extending their nighttime fast and restricting eating to within an eight- to 12-hour window.
Studies have shown that shift workers experience more chronic health problems than non-shift workers, particularly cardiovascular and gastrointestinal diseases, diabetes, and obesity — and in 2007, the World Health Organization even classified shift work as a potential carcinogen. According to Dr. Panda, “we are all shift workers,” living at odds with our own internal rhythms because of disrupted or irregular sleep and meal schedules. He and his colleagues at the Salk Institute for Biologic Studies have shown that all of our organs — and every one of our cells — is governed by an internal clock that is programmed to turn on or off thousands of genes throughout the day and night, and that by optimizing our clocks, we can prevent — and even reverse — chronic ailments.
Here, Dr. Panda tells CoveyClub how living in sync with your circadian rhythms can not only enhance your health, but can lead to weight loss, increased energy, and better sleep.
TheCovey: You write in The Circadian Code that adjusting the timing of how we live will surely be the next revolution in health care — and that by restoring our circadian rhythms, we can even reverse chronic diseases. Can you discuss how focusing on the timing of eating and sleeping can impact our health?
Dr. Panda: Many chronic metabolic diseases, including prediabetes, type 2 diabetes, high blood pressure, and high cholesterol, can arise from circadian rhythm disruption. In fact, there are controlled clinical studies where healthy people are brought in and their sleep is disrupted — they are put into states similar to those produced by jet lag or shift work — and within a week, the body doesn’t function that well and they can become prediabetic or their blood pressure can increase. Most of the studies show how disrupting the circadian clock leads to disease, but the reverse, how to fix our clock, wasn’t well studied, because it’s really hard to make people consistently sleep for seven or eight hours, or avoid light at night. That’s why we focus on another aspect of circadian rhythms, and that’s metabolism or eating/fasting rhythms. When people eat within a consistent window of 12, 10, or eight hours, they nurture their circadian rhythms and their organs function optimally. This ultimately leads to better health and mind.
TheCovey: You and your colleagues have shown that just as the first light of the morning resets our circadian clock, the first bite of the morning resets other organ clocks. How does this happen? And what should that first bite be — or, perhaps, when should that first bite be is a more pertinent question?
Dr. Panda: In the last 10 years, we have learned a lot more about how these clocks work, and one interesting thing that has emerged is that the night hormone melatonin that makes our brain sleep also makes our pancreas sleep. And after we wake up, it takes almost a couple of hours for melatonin to go down to daytime levels. So that means within an hour of waking up, we have enough melatonin to inhibit our pancreas. Our pancreas, which plays an essential role in regulating blood sugar and digestion, is still sleeping. That’s why one should wait for an hour or two after waking up to have the first bite of the day, so that the body will be ready to process the food.
TheCovey: What happens in the body when we take that first bite?
Dr. Panda: Before we even put something in our mouth, our sensory system sends signals to the brain and we start to salivate, which produces enzymes to break down the food. As food gets to the stomach, the stomach wakes up and produces enough acid and digestive juices to break up the food. Within 10 to 15 minutes, our gut starts to absorb nutrition, including glucose from the cream and sugar in our coffee. Many studies have shown that this initial response to food also tells the clocks in various organs that the day has started, so the clocks synchronize and align themselves to the eating/fasting schedule.
TheCovey: You write in your book that even your first sip of coffee counts as your “first bite.” Must we really forgo that early morning cup in order to reap the benefits of time-restricted eating?
Dr. Panda: Nine out of 10 people drink coffee with a lot of cream and sugar, and that would break the metabolic fast. Black coffee can also reset our clock, but without increasing blood sugar. So these days what I say is that there are three exceptions to the rule: You can have black coffee if your job depends on it — a lot of people wake up very early and have to get in front of a laptop or on a conference call; second, if you have to get up and drive — we don’t want people to be sleepy and driving; and third, if coffee is the only love of your life. So black coffee is okay, but it depends on what health issue you are trying to solve. For weight loss or blood glucose control, black coffee doesn’t make much of a difference. But if someone is trying to fix their gut problem and the goal is to reduce acid reflux, having coffee on an empty stomach might not be the best thing.
TheCovey: Much of the diet advice to date has focused on what we should and shouldn’t eat. Though you do point out that for best weight-loss and overall health results, it makes sense to follow a balanced diet with plenty of fruits and vegetables, lean proteins, and healthy fats, are you saying that WHAT you eat is less important than WHEN you eat?
Dr. Panda: So the importance of when you eat is so powerful that it can reverse the bad effects of bad food — we’ve seen this in mouse studies. But that doesn’t mean you should eat bad food within that 10-hour window. In most of our human studies, when people eat within 10 hours, and have their dinners three hours before sleep, they reduce their alcohol intake — and the poor food choices that go with alcohol — so they are improving their diet quality by eliminating extra alcohol. And since they are hungry enough in the morning after 14 hours of fasting, they are more likely to eat a healthy breakfast. We don’t know why, but people doing TRE [time-restricted eating] also cannot eat too-salty or too-sweet food. So indirectly, we improve nutrition quality. At the same time, just like the healthy food on a dirty plate is unhealthy, healthy food at the wrong time can make that food unhealthy.
TheCovey: Does focusing on when you eat, sleep, and even exercise compensate for those times when you make less-than-exemplary food choices?
Dr. Panda: Yes, it does compensate for bad food choices. For example, if in the morning you have a big breakfast, you are less likely to snack on a Danish or pastry in the office. Another reason why we think food choices improve is that people who do TRE also sleep well. Their sleep satisfaction increases significantly. And if sleep-deprived people make a lot of wrong choices about food, a well-slept brain makes good choices about food. So some of the benefits may be an indirect effect of sleep.
TheCovey: How does TRE help you lose weight? Can you explain why the fat-making process stays on all the time when eating occurs at random times through the day and night?
Dr. Panda: Any time we eat, our pancreas produces a little bit of insulin and that insulin is a signal to make fat. So insulin causes liver cells, fat cells and muscle cells to absorb that glucose from blood and at the same time turns on other biochemical processes that convert that glucose to glycogen and also to fat. So for example, even after I have a small bite of cookie, my insulin response may turn on for an hour or two — so for the next one or two hours, my body is not prepared to burn any fat, but is programmed to make and store fat. So if you keep eating throughout the day, you’re constantly programmed to make and store fat.
TheCovey: Aren’t there also genes that get stuck in the on or off position, leading to diseases like type 2 diabetes or liver disease?
Dr. Panda: Yes, genes that are supposed to be off during fasting don’t get a chance to turn off, and the genes that are supposed to turn on a few hours after fasting don’t turn on. We can completely reprogram thousands of genes in different parts of our bodies by just deciding when to eat and when to fast.
TheCovey: Why is eating — and drinking alcohol — at night particularly detrimental to our health and our efforts to live in sync with our body’s internal rhythms?
Dr. Panda: After we eat our last meal, it takes almost five hours for our stomachs to empty and digest that food. If we had our last meal at 6 pm, our stomach is working until 11, and only after that is the stomach ready for repair. During that time, from 11 until 7 or 8 the next morning, the stomach needs repair, because every day we damage somewhere between 7 and 10 percent of our stomach lining. It’s like a cobblestone street, and 7 to 10 percent of those stones are damaged and need to be repaired. Now, repairing the road requires the repair crew to come in and also the traffic has to stop. The repair crew in our body is growth hormone that is secreted in the middle of the night when we are deep asleep. If the repair crew comes and the traffic is still flowing, then that repair doesn’t happen.
So we still have damaged cobblestones — or cells — and since the cells are damaged, the gut is leaky, and can let alcohol seep into the blood more easily if someone drinks late at night. New studies are showing that night shift workers are more likely to increase their blood alcohol level much faster than those who don’t do shift work — their gut lining repair and alcohol metabolism is strongly disrupted by sleep/wake and eating disruptions. The advantage of having a clock is that it helps the body anticipate what’s going to happen. Just like before we wake up, the clock increases our core body temperature, breathing and our heart rate, similarly, if we maintain a consistent dinner time, then the clock also learns that dinner time is when the kitchen is closing every day and it can prepare our body to repair itself.
TheCovey: You write in your book that addressing your circadian clock is not just about knowing when to eat, but also when to turn off the lights. Why do you call lights and screens the “ultimate disrupters,” and how might we hack our lighting to help us live in sync with our natural circadian rhythms?
Dr. Panda: Daylight is very rich in blue light, and blue light is the color of light that is most effective in synchronizing our brain clock. In the first half of the day, try to get some daylight. It can be sitting next to a large window if you cannot go outside on a cold day, or even walking on a cloudy day for 30 minutes — that’s enough light to synchronize our brain clock, and tell the body that it is daytime. If you’re working in a brightly lit office room, lit by bright LED, that should also be okay. Then, in the evening, two to three hours before going to bed, try to avoid bright light because that bright light will reduce your sleep hormone melatonin and make it difficult for us to sleep. Use a filter on screens, avoid going to stores with bright lighting, and use task lighting rather than overhead lights.
TheCovey: Why do you say that when and how you wake up is the most important event of the day?
Dr. Panda: If you require an alarm clock to wake up, that means you haven’t slept enough. And if you wake up and remain in the dark, and don’t get enough light for the next hour or so, your melatonin levels remain high. So if you’ve forced yourself to wake up, are not exposed to bright light, have high melatonin, and reach for your breakfast coffee and muffin, you are putting a lot of stress on your body, because you’re not producing sufficient insulin to process it.
TheCovey: What changes can we make at or before bedtime to optimize sleep — and why is optimizing sleep so important to our circadian code? How do we compensate for the sleep debt that accrues because of insomnia? Do naps disrupt our circadian rhythms?
Dr. Panda: To optimize sleep, avoid food and avoid light two to three hours before going to bed. Having a shower in the evening also helps, because it drives blood away from the core and to the skin, and the core temperature drops, which tells us to sleep. And maintaining a cool bedroom or bed helps, so choosing your bedding material is very important. Some mattresses, especially those that use foam, can absorb heat and cool you quickly, but they reflect back that heat at 2-3 in the morning and people wake up with a warm body and can’t go back to sleep.
Naps are fine: We humans are programmed to have naps in the afternoon. The interesting thing is that during daytime, having two to three hours of darkness is not going to reset our clock, but at nighttime, having an hour of light will. Keep naps within an hour so you don’t delay your sleep time at night.
TheCovey: Why is waking up with joint pain a sign that you are not getting enough sleep?
Dr. Panda: Joint pain is essentially a sign of inflammation, and sleep deprivation can increase inflammation because in the middle of sleep we get this growth hormone that repairs damaged tissue and helps to reduce inflammation throughout the body.
TheCovey: How does one compensate for celebrations or weekend social plans that may extend the eating/drinking window despite our best efforts? If you go off track for an evening or a weekend, can you still reap the benefits of TRE?
Dr. Panda: We have done an experiment where we give mice the weekends off, and those mice still get most of the benefits, if not all, from five days of TRE. In our recently published human trials, we found that most people could do 10 hours TRE for five to six days, and even if they ate once in 10 days outside this window, eating for up to 12 or 13 hours, we still saw benefits in terms of weight loss, blood pressure and blood sugar.
TheCovey: How might a person assess their own circadian rhythms, and determine a reasonable window for time restricted eating? You advise people to begin by keeping their eating within a 10- to 12-hour window, but can you choose any 10-12 hours?
Dr. Panda: The best approach is to figure out what are your hard deadlines of the day in terms of waking up. So, for example, if you have to wake up at 6, you work backward, and make sure you go to bed at 10, no later than 11. Then, for 12 hours eating, if having dinner with your family at 7 or 8 is important, then back it up from there and see when you should have your breakfast. In our clinical studies, we always ask people to take these factors [into account] and self-determine when they can eat.
Now we put everything together: Everything about sleep, light, food, melatonin, the pancreas. We’ll begin the day the night before. Try to be in bed for eight hours so that you can sleep, if you are an adult, for seven to seven and a half hours. After waking up, wait for an hour or two before the first bite of the day. Even if you have black coffee first thing, waiting a couple hours before the meal is beneficial. Then, after the first bite, depending on what you can do, eat within eight,10, 11, or 12 hours, not more than 12, decide when should be your last meal, and make sure your last meal is two to three hours before going to bed. Avoid food and avoid bright light two to three hours before bedtime. Remember to step outside for at least 30 minutes to get daylight after you wake, because daylight synchronizes the brain clock. And repeat….