If you want to check in with yourself on the quality of your life, there’s probably no better metric to look at than your energy level. When you have tons of energy, life is generally good. When you don’t . . . well, not so much.
These days, lots of us don’t have much energy. Perhaps you’ve noticed. We’re tired. We’re dragging at work. We can’t wake up in the morning, and when we do drag ourselves out of bed, we’re
groggy. Irritability—an inevitable accompaniment to fatigue—is a constant presence. Our work suffers, our sex life suffers, our relationships suffer, our health suffers.
So what’s up with that? Why are we so tired all the time?
One of the principles of science is called the principle of parsimony, which holds that the simplest explanation for a phenomenon is often the best one. Or, as one of Jonny’s professors once said, “When you hear hoofbeats outside your window, don’t start off looking for zebras.” In other words, when you’re looking for an explanation, begin with the obvious (in the case of the hoofbeats, look for a horse). The obvious cause for our flagging energy is right under our noses: We’re not sleeping enough.
It’s All About the Rhythm
Before the invention of electricity, we were much more in tune with our biological, or circadian, rhythms (from the Latin circa, “around,” and diem, “day”). Brainwave activity, hormone production, and all sorts of other regulatory metabolic functions are deeply connected to our circadian rhythms.
These same rhythms that are such an essential part of our biological makeup are actually triggered by external events, the most important of which are light and dark. Our bodies essentially come preloaded with the software for sleeping when it’s dark and waking when it’s light. When our sleep patterns deviate from this programming, metabolic and hormonal systems break down and all kinds of problems occur (which is one of the many reasons why shift workers are plagued with so many health issues).
Sleep affects how we work, how we relate to people, how we perform, how we make decisions, how much energy we have, and how we feel overall. The effect of sleep, or lack of it, is profound and probably influences every metric of our existence. Sleeping too little depresses our immune systems, raises our stress hormones, and, incidentally, makes us fat. (We knew that would get your attention.)
The Wake-Up Call: Weight Gain
If the connection between gaining weight and not sleeping enough comes as a surprise, consider this. Sleep greatly affects your hormones, and when it comes to weight gain, hormones basically run the show. Sleeping poorly, or not sleeping enough, throws a monkey wrench into the complex interplay of hormones that control appetite and body weight.
Research has found that short sleep duration is associated with reduced leptin (the hormone that tells your brain you’re full) (see Chapter 2 for more on leptin). For a double whammy, it’s also associated with increased levels of ghrelin (a hormone that signals to the brain that you’re hungry), virtually compelling you to eat. With less of the hormone that tells you you’re full, and more of the hormone that tells you you’re hungry, it’s no wonder scientists have long observed an association between short habitual sleep time and increased weight.
It gets worse.
Recent research has shown that not getting enough sleep reduces the ability of your cells to respond to insulin. You may recall the ability of the cells to “listen” to insulin—a desirable state of affairs called insulin sensitivity (see Chapter 2). This is a hallmark of healthy weight and of good health in general. Its opposite, insulin resistance, is an undesirable state of affairs that happens when the cells no longer pay attention to insulin. The cells, particularly the muscle cells, close their doors when insulin comes calling with its sugar payload. The sugar winds up going to the fat cells (and
everyone knows how that story ends). Insulin resistance, as you learned earlier, is a hallmark of both diabetes and obesity, and a big risk factor for heart disease.
Lack of sleep makes you insulin resistant. And no matter how brilliantly you are eating, if your insulin isn’t working properly—if the cells aren’t listening to it—you’re likely to get fat. Are you beginning to see why sleep is so essential to your success with the Smart Fat Solution?
In one study, J. L. Broussard and colleagues at the University of Chicago had seven healthy, lean young adults live in a sleep laboratory for four days on two occasions spaced about a month apart.
They ate identical meals and were not allowed to eat snacks. In the first part of the study, the subjects spent 8½ hours in bed for each of the four nights in the sleep lab. For the second part of the study, they slept only 4½ hours a night, so that by the end of the second part of the study they were sleep-deprived by about fourteen hours.
After each four-day period, the researchers measured the participants’ insulin response. They also collected fat cells in order to measure how those fat cells reacted to insulin after fourteen hours of sleep deprivation.
The results were not encouraging. After only four nights of sleep deprivation, the participants’
overall ability to respond to insulin had decreased by 16 percent—and that’s in healthy young subjects after only four nights of not sleeping enough! One can imagine the metabolic havoc wrecked upon older, less resilient adults after years of not sleeping enough. It’s not a pretty picture.
Exactly what happens when we sleep, and why we need sleep in the first place, remains a bit of a mystery—even to scientists who study this stuff. And although scientists don’t fully understand exactly why our bodies need sleep, they know that they do. Sleep generates hormones, such as human growth hormone, the ultimate “anti-aging” hormone that’s released only during the deep stages of sleep.
(Human growth hormone helps you build muscle and burn fat, while stimulating cell reproduction and regeneration.) During deep sleep your body also produces melatonin, a hormone that helps regulate the sleep cycle and also has some anticancer activity to boot.
While a good night’s sleep has a positive effect on hormones, a lack of sleep has a negative effect. Lack of sleep is a huge stressor on the body, which causes you to release more cortisol (the stress hormone), which, as you’ve seen, can create belly fat, break down muscle, shrink the brain, and depress the immune system. (It can also make you overeat like crazy.)
The Architecture of Sleep (and What Happens When the Foundation Cracks)
To appreciate just how important sleep is to your health—and why extended, uninterrupted, deep, and restful sleep may be one of the most important things you can do to manage your weight and regain your health—it helps to know something about what’s called sleep architecture. Sleep can be divided into two categories: REM (rapid eye movement) sleep and non-REM sleep.
Non-REM sleep is divided into four stages. Stage one is that period when you first move from wakefulness to drowsiness to falling asleep. (Think of nodding off late at night while watching television.) In stage two, eye movements stop, brain waves begin to slow, muscles start to relax, heart rate slows, and body temperature starts to drop. Stages three and four are together known as slow wave sleep and are characterized by brain waves known as delta waves. During slow wave sleep, your blood pressure and body temperature drop a bit more, breathing slows more, and the body becomes immobile. (This is what we call the “dead to the world” phase.)
And then there’s REM sleep, the jewel in the crown, the pièce de résistance of deep, restorative
sleep. This is when the cast of characters in your own personal dreamland come alive and dance.
(REM sleep is the only stage when you dream). One complete sleep cycle consists of the four stages of non-REM sleep plus REM sleep and takes a total of about 90–110 minutes. Ideally, the cycle is repeated about four to six times a night.
But as we age, everything changes. It takes longer to fall asleep. The percentage of time we spend in each stage changes; we spend a little longer in stages one and two, and a little less in stages three, four, and REM sleep (meaning we spend just a little less time in deep sleep). Regardless, normal healthy adults should still spend about 25 percent of their sleep time in REM sleep—and when this is disrupted, all kinds of stuff happens, none of it good. (There’s a reason why sleep deprivation is used as a torture technique.)
We’ve already discussed how sleep affects weight and how not sleeping enough increases stress.
But sleep is also essential to memory, mood, and cognitive performance. Lack of sleep is linked to increased anger, anxiety, and sadness—all metrics for a poor quality of life. One study showed that when subjects were permitted to sleep only 4½ hours a night, they exhibited significantly more stress, mental exhaustion, and anger.
Sleep also affects immunity. In one clever study, researchers gave flu shots to two groups of men.
The first group was allowed to sleep only four hours a night for four nights, while the second group was allowed to sleep normally. Ten days after getting the flu shot, the sleep-deprived group had a significantly lower immune response than the normal-sleeping group. In fact, the under-sleepers actually produced less than half as many flu-fighting antibodies!
The bottom line: Pay attention to your sleep. Saying “I’ll sleep when I’m dead” used to be a badge of honor among Type-A personalities, but the irony is that those who say that may well die sooner rather than later. They are not paying attention to the huge metabolic, hormonal, and anti-aging benefits of deep, restful sleep.
Sleep Recommendations: The Art and Science of Catching Forty Winks
We want you to make getting a good night’s sleep—every night of the year—a priority. It’s essential for your health, your longevity, your performance, and your waistline. And although people may vary in their individual sleep needs, we think seven hours a night is the magic number needed for optimal health. (Steven sleeps seven to eight hours, Jonny sleeps six.)
Some tips for better sleep that we’ve found helpful over the years include:
Keep the room dark. Studies show that even dim light can disrupt melatonin production.
Harvard sleep researcher Stephen Lockley notes that light at night is part of the reason so many people don’t get enough sleep.
Keep the room cold. Sleep experts say that the ideal temperature for sleep is around 68 degrees. A mild drop in body temperature helps induce sleep, and it’s easier for that to happen if you’re in a cooler room.
Never fall asleep with the TV on. There’s nothing soothing and restful about a subliminal soundtrack of news, infomercials, and reruns of the Kardashians. That TV soundtrack gets into your brain, disturbs your sleep, and frequently causes dreams of Thighmasters and Insanity.
You may feel that you need the TV on to soothe you to sleep, but really, you don’t. Try silence. You’ll sleep better.
Not only is the amount of light important, but different types of lighting help you to wake up and to go to sleep:
Wake up to bright light; it matches your cortisol surge in the morning and helps wake you. If you can get out in the sunlight first thing in the morning, that’s awesome. If not, consider wide-spectrum bright lighting for the first thirty to sixty minutes after you wake in the morning.
Use red-orange light before you go to sleep, especially if you suffer from insomnia. One to two hours before bedtime, wear red-orange glasses or turn your bedroom into a red-light room. Red light simulates sunset and bedtime for humans and stimulates your brain to produce melatonin and put you to sleep.
Avoid white-background TV or computer screens one to two hours before going to bed as white light tells your primitive brain to wake up.