Have you committed to a new healthy eating routine this year? Wondering how sleep can assist in making your healthful dietary choices easier to stick to and more effective? These are some of the most potent sleep and diet connections that even nutritionists often miss.
Sleep can stimulate fat-burning fat
Tip: Sleep naked and in a cool environment
Our bodies contain several different types of fat, and they perform different functions. Certain kinds of fat actually work to burn energy, rather than storing it. White fat stores energy, brown and beige fat actually burn calories, and keep insulin working properly, help regulate blood sugar, and guard against obesity. Studies in mice show that animals with higher amounts of brown fat are leaner, and have better metabolic health. Research involving humans has shown brown fat is linked to lower body mass. On the other hand, a lack of brown fat in mice is associated with higher insulin resistance, higher blood sugar, and diabetes. Scientists have discovered beige fat activates a protein that works to burn calories and generate heat in the body, and may have significant benefits in combating obesity and metabolic disorders. Basically, this is the fat you WANT!
How does sleep affect these good-for-your-metabolism fats? Healthy sleep contributes to the increase of these fats in a number of ways. Melatonin supports the production of both brown fat and beige fat. Research has shown that higher melatonin levels are linked to more of these fat-burning fats. Scientists think that melatonin stimulates beige and brown fat at least in part by helping to convert white fat into these other energy-burning fats, and by helping the body be more responsive to the effects of cool temperatures. (More on how these fats interact with ambient temperature in just a minute.)
Sticking to a consistent sleep-wake cycle and protecting daily circadian bio rhythms from disruption (by doing things like guarding against too much light exposure in the evenings) are ways to encourage your body’s natural melatonin production, which in turn may help your body make more of these weight-loss promoting fats.
Both brown and beige fat are sensitive to temperature, and can be stimulated by exposure to cool nighttime temperatures. Research shows sleeping overnight in cool environments increases brown and beige fat, by triggering the body to convert white fat to these energy-burning fats.
You might not expect to hear your nutritionist tell you to sleep in a cool bedroom and to sleep in the nude. But both of those simple, sleep-promoting strategies can spur your body to generate more of the kinds of fat that encourage weight loss and a healthier metabolic profile. Bonus: a cool room and sleeping naked also can lead to more comfortable, restful sleep—and more sex!
Melatonin is a MAJOR player in weight and appetite control
Tip: Keeping a regular sleep schedule will help control melatonin production, and your weight.
Most people think of melatonin as a sleep hormone—and they’re right. It’s a significant regulator of sleep. But melatonin’s impact on health goes way beyond its influence on sleep-wake cycles. (I just wrote about some of the most interesting scientific advances in our understanding of how melatonin affects health.) One under-recognized role that melatonin plays? As a guard against obesity and metabolic dysfunction.
Melatonin is an important regulator of the body’s energy balance, or homeostasis—that’s the balance of energy intake (through calories) and energy expenditure. Research demonstrates that a lack of melatonin is linked to a reduction in the effectiveness of leptin, a hormone that controls hunger by signaling fullness or satiety—essentially sending the message that the body has taken in enough energy through food, and it’s full. Restoring melatonin to healthy levels can improve leptin’s effectiveness, reduce food intake, lower body weight and reduce unhealthy fat stores in the body.
Melatonin, as I’ve mentioned, also affects how well brown fat works to keep metabolism on track. Melatonin is involved in the process by which the body converts white fat to brown fat, and heightens the body’s response to cold temperatures, which stimulates production of brown and beige fats.
Light exposure affects melatonin—and ALSO hunger hormones and metabolism
Tip: Getting sunlight or spending time in a well-lit work environment helps regulate your hunger hormones.
Like you, your nutritionist probably knows that melatonin production is primarily influenced by exposure to light and darkness. The absence of light triggers the nighttime increase in melatonin levels that help bring about sleep on a nightly basis, and help the body to maintain a consistent, refreshing sleep-wake routine day after day. On the other hand, evening light exposure suppresses melatonin.
What your nutritionist may not know? Light exposure throughout the day also has direct effects on hunger hormones, and on other key components of metabolism. Studies show that morning light exposure can increase leptin (an appetite-suppressing hormone) while reducing ghrelin (an appetite-stimulating hormone). Morning light exposure is also good for daily melatonin cycles, too. Evening light exposure, of light containing high concentrations of blue light, has been shown to have a range of negative effects on metabolism and appetite, including increasing blood sugar, decreasing insulin sensitivity, and boosting sugar consumption.
The relationship between light exposure, sleep and metabolism is complex. For all we know about the interrelationship among these factors, there’s a tremendous amount that’s still waiting to be understood. What’s clear? Being thoughtful and deliberate about light consumption is an under-used tool to help manage weight and metabolic health.
Better sleep can kickstart a stalled-out weight-loss plan
Tip: Research shows that getting enough sleep AND sticking to a regular sleep routine together can help you break through a weight-loss plateau.
It’s a frustration familiar to many of us: you’ve been working hard, sticking to a healthy eating plan, exercising regularly, and then suddenly—nothing seems to be working. The pounds stop coming off.
If you’re a regular reader, you know how often I tout the importance of consistency in sleep schedules. Regular bedtimes and wake times protect sleep quality, make falling asleep easier and faster, and ensure you get the right amount of sleep you need for you. Consistent sleep routines boost circadian rhythms—and healthy bio rhythms in turn help to improve sleep. Circadian rhythms also contribute to a healthy metabolism, sharper cognitive function, and a stronger immune system.
Recent research demonstrates that consistent sleep routines may help you kickstart a stalled-out weight loss goal. A study published recently in the International Journal of Obesity looked at how sleep amounts and the degree of variability in sleep schedules affect weight.
Scientists tracked sleep, weight, and measurements of body fat (including waist circumference and BMI) in a group of more than 1900 overweight and obese adults, for a period of 12 months. People who stuck to a more routine sleep schedule, with less variability in bedtimes and wake times, lost more weight than people whose schedules were less regular. The more consistent sleepers also saw greater positive changes to BMI, or body mass index.
Sleep amounts also mattered to weight loss. People who slept 7-9 hours a night lost more weight than people who slept less than 6 hours. The longer sleepers saw greater reductions in waist circumference fat.
Sleep burns significant calories
Tip: Know what you burn in bed!
You—and your nutritionist—might be surprised at just how much calorie burning goes on during sleep. What’s behind this sleep-time energy consumption? The body does a lot of work during sleep, and that requires a steady stream of energy. Some phases of sleep require significantly more energy than others to fuel the body, including REM sleep, when the brain is highly active, and the deep sleep stages 3 & 4, when cells, tissues are undergoing major restoration and repair. It’s estimated that our metabolic rate—the rate at which we burn calories through the body’s biochemical processes—drops by only about 15% during sleep, compared to when we’re awake. That metabolic rate—the work it takes for the body to function, whether asleep or awake—accounts for roughly 80% of ALL calories burned during a 24-hour day. The remaining 20% is burned through physical activity.
The exact number of calories burned during your nightly sleep depends on a number of factors, including your weight, age, body temperature and, of course, the amount of time you spend asleep. Other factors include gender and individual genetics. It is possible to calculate your metabolic rate, and use it to estimate the number of calories burned during a typical night of sleep. You’ll use a formula known as the Harris-Benedict equation, and you’ll need accurate measurements for your weight and height, as well as the number of hours you sleep in a night—and your age. Here’s how to do it:
BMR (that’s basal metabolic rate) equals:
665.1* + (weight in pounds x 4.34) + (height in inches x 4.7) – (age in years x 4.68)
(*I know, this 665.1 number looks like it might be a typo, when you compare it to the calculation for men, below. It’s right, though. You can read more about this equation for men and women here and here.)
66.47 + (weight in pounds x 6.24) + (height in inches x 12.71) – (age in years x 6.78)
So, for a 50-year old woman who weighs 140 pounds and is 5 feet, 4 inches, BMR would be:
665.1 + (140 x 4.34) + (66 x 4.7) – (50 x 4.68)
665.1 + 607.6 + 310.2 – 234 = 1348.9 calories per day
To figure out how many calories you burn during sleep, you’ll first need to determine your hourly metabolic rate.
That’s BMR / 24. In the case of the 50-year old woman above, 1348.9 / 24 = 56.20 calories per hour
Multiply that number by the number of hours you sleep. Let’s say our 50-year-old woman sleeps 7 hours a night.
56.20 x 7 = 393.43 calories in 7 hours
Last step is to account for the 15% reduction in metabolic rate that occurs during sleep. Multiply the number above by 0.85.
393.43 x 0.85 = 334.41
That 50-year old woman burns about 334 calories during her 7-hour nightly rest—that’s a good, rigorous half-hour jog on the treadmill!
Keep in mind: it doesn’t make sense to skip your exercise because you think you are burning enough calories in your sleep. Exercise offers many benefits that are helpful for sleep. But don’t write off sleep as a time to burn meaningful calories, along with all the other essential restorative work that sleep provides.
Lack of sleep is directly connected to junk-food cravings
Tip: Take a nap, don’t eat a cookie for energy
We’ve all had the experience of being tired and overwhelmed by the temptation of junk food. (I head straight for the ice cream.) But you and your nutritionist may not know just how deeply a lack of sleep is involved in those junk food cravings. There are a few different mechanisms by which sleep directly impacts our appetite for sweet, salty, fatty and processed treats. Hormonal changes brought about by poor sleep are one major factor here. When we’re sleep deprived, cortisol levels are high and serotonin levels are low. Under these hormonal conditions, our bodies typically begin to crave starchy, sugary and fatty foods, as a way to help boost serotonin and calm stress. At the same time, lack of sleep increases the hunger hormone ghrelin and suppresses the satiety hormone, leptin, which signals when we’ve eaten enough. The combination of these sleep-induced hormonal shifts can result in some pretty difficult-to-resist cravings for junk food.
Insufficient and poor-quality sleep also change our cognition in ways that affect our ability to make healthy decisions. Research shows that the impact of sleep loss on judgment and decision making can have a negative impact on food choices, sending us in search of that potato chip bag or pint of ice cream we might otherwise have the capacity to avoid. Not getting sufficient sleep impairs the function of the brain’s frontal lobe, where our higher-level decision making occurs. At the same time, the areas of the brain that respond to immediate rewards are activated by sleep loss.
Lack of sleep leads to a BIG boost in calorie consumption
Your nutritionist likely knows that sleep affects calorie intake, but may not know just how big an impact sleeplessness can have on consumption. This 2016 review of sleep-metabolism research found that partial sleep deprivation, the kind of chronic sleep debt that so many busy adults live with, leads to consumption of an average of 385 additional calories a day.
Remember your calculations about burning calories in your sleep? This looks pretty close to reversing all that weight loss.
That’s the caloric equivalent of a muffin from your local cafe. In that same study, researchers found changes to the macronutrient content of what people ate. When sleep deprived, people consumed less protein and more fat. Sleep as a tool for weight loss and metabolic health can be measured in many ways—including in its direct impact on daily calorie consumption.
Michael J. Breus, PhD, DABSM
The Sleep Doctor
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