In a culture where self-worth is measured by our accomplishments, we rarely focus on the benefits of relaxation! It’s time to set your to-do list aside and focus on making sleep a priority. Catching your zzz’s at night has a profound impact on your appetite, food choices, and mental function. Researchers have even associated the number of hours you sleep with your ability to maintain a healthy body weight.
Why focus on sleep?
The Meriam-Webster dictionary beautifully defines sleep as, “the natural periodic suspension of consciousness during which the powers of the body are restored.” Doesn’t that sound profound? Every single night we have the opportunity to restore the powers of our bodies by simply closing our eyes and sleeping.
What happens during sleep?
Waste Removal. Have you ever wondered how the brain cleans and refreshes itself? Our bodies use the lymphatic system to remove toxic waste that accumulates as a result of everyday metabolic processes. Unlike the rest of the body, the brain doesn’t directly use the lymphatic system for waste removal. University of Rochester neurosurgeon Maiken Nedergaard coined the term “glymphatic system” to describe the mechanism by which the brain releases waste. The glymphatic system uses the cerebrospinal fluid (CFS) to flush neurotoxins down through the spinal column. And there is no better time for the brain to rinse out toxins that during sleep. Nedergaard’s research team discovered “hidden caves” that open in the brain while we sleep allowing CFS to flow deeply into the interstitial spaces of the brain and more efficiently clear out toxins. Among the long list of waste byproducts is beta-amyloid, a protein that clumps together and forms plaques within the brains of people with Alzheimer’s disease. Although you may be physically resting, the brain is actively clearing out any unnecessary build-up to prepare you for the following day’s work!
Hormone Release. During sleep, our brain is actively releasing hormones to bring the body into balance. The levels of two important appetite-regulating hormones are impacted by sleep time: leptin and ghrelin.
- Leptin is the satiety hormone secreted by white adipocytes (fat cells). It acts on the hypothalamus center in the brain to suppress intake and stimulate energy expenditure. Levels increase to create a sensation of fullness after a meal.
- Ghrelin is the hunger hormone, produced by specialized cells within the GI tract (mainly the stomach & pancreas). Levels increase when the stomach is empty, and decrease once the stomach becomes stretched after meals. Ghrelin communicates with the hypothalamus to increase hunger, increase gastric acid secretion, and increase GI motility to prepare the body for food. Interestingly, it also plays a role in reward perception in dopamine neurons. Ghrelin interacts at the neuronal site that plays a role in sexual desire, reward, reinforcement, and addiction.
These two hormones counterbalance one another by communicating with the hypothalamus to regulate appetite. How does sleep play a role in this interaction? Ghrelin levels are significantly increased after sleep restriction. Simply put, increased ghrelin = increased hunger. Furthermore, leptin levels are lower, so your brain is not receiving a message of satiety. The result of this hormone imbalance: when you are sleep deprived, you are more likely to eat more than your body truly needs. A Mayo Clinic study found that over a 1 week period, sleep deprived adults consumed an average of 559 additional calories per day when compared to well rested counterparts!
When you are trying to learn the natural hunger / fullness cues of your body, it is important to ensure you are getting adequate rest. Otherwise, you may find that it is difficult to satiate that feeling of hunger. Getting a full night’s sleep will give your appetite-regulating hormones a chance to come into balance. That way, you can trust your brain to let you know when your stomach is truly full.
Metabolic Reset. Losing out on sleep results in a decreased resting metabolic rate and is linked to unhealthy weight gain. A Harvard Medical School study found that healthy adults with inadequate sleep (5.6 hrs sleep per night for 3 weeks) had slower metabolic rates and increased glucose levels after meals. Sleep deprivation also increases the body’s resistance to insulin, a hormone that works to absorb glucose and convert it to energy for your cells. This means that blood sugar levels rise and the glucose is not properly utilized by the body, which increases your risk for diabetes and obesity. There is even a correlation between hours of sleep and likelihood of excess weight gain. Adults who get only 6 hours of sleep per night (which, for many people I know, is considered a full night sleep!) are 23% morel likely to be overweight. Those sleeping less than 4 hours per night are 73% more likely to gain excess weight. Getting adequate sleep (a minimum of 7-8 hours per night) will help your body find balance at its healthy weight.
Memory Consolidation. Your brain does an incredible job of interpreting all of the sights, sounds, tastes, and smells you experience during every second of your waking hours. Have you ever thought about all of the organization it must take for your brain to process so much, so quickly? Sleep is a time for your brain to consolidate information into memories. All of the learning throughout the previous day is encoded and stored during sleep, solidifying new memories for you to access once you awake. During a time when you are working on making healthy changes in your life, allow your brain time to process the information and establish new neuronal networks.
Protection from Overstimulation. Images of food are among the list of stimuli our brains receive during the day. These images communicated with the brain to impact appetite and desire to eat. Researchers have found that when we are sleep deprived, reward centers of the brain experience increased stimulation in response to food stimuli. Within the brain, neuronal activity is actually altered after a period of restricted sleep. Interestingly, researchers saw that an overtired brain begins to act similar to one of an underweight person attempting to restore weight (3, 4). This means that we are predisposed to overeat when we are over tired.
In a society where we are constantly inundated with food advertisements and fast-food chains, our brains are overwhelmed! A well-rested brain is able to respond to food stimuli in a conscious way, rather than reacting as if the body is in a state of starvation. One study actually found that the brains of sleepy women had a more difficult time moderating intake in response to food stimuli than those of sleepy men (5). Giving your brain a break at night prepares it to support your healthy eating habits during the day.
Dreams. Although dreams may not be directly connected with your food intake, I am a huge believer in listening to the messages communicated from our subconscious mind through dream imagery. Sigmund Freud has said, “I believe that these unconscious wishes are alway active a ready to express themselves with an impulse from consciousness.” My favorite of the great psychologists, Carl Jung, believed dreams communicate, “ineluctable truths, philosophical pronouncements, illusions, wild fantasies, memories, plans, anticipations, irrational experiences, even telepathic visions.” To try and make sense of this powerful dream imagery, I have a regular practice of recording dreams in the morning (either written in a journal or aloud using the voice recorder on my phone). Connecting with the messages of your subconscious mind is a powerful way to deeply process difficult emotions. There is even a practice of calling to mind a particular question or issue at bedtime. You set an intention to allow your dreams to communicate your innermost thoughts and feelings on the topic to help you gain clarity and understanding.
As opposed to referencing books on dream imagery to determine the dream meanings, reflect on the dream as a whole, within the context of your own life. The following are some questions I ask myself when interpreting a dream:
- Where am I? Do I know this space? How am I feeling in this setting?
- Who am I interacting with? Do I know any of these people/animals? How do I feel about them?
- What particular colors, numbers, or names can I recall?
Use your answers to these questions to determine what the dream is trying to communicate with you. It is important to remember that your feelings within the dream are more important than deciphering each tiny detail. Dreams don’t typically follow a logical storyline, so don’t get hung up trying to organize the chaos of the scene!
Final thoughts…
Simply put, sleep is a vital component of a healthy lifestyle. Adequate sleep allows your brain to refresh, balance hormones, solidify memories and more efficiently process information. If your brain is overtired, it may be influencing your food choices more than you previously realized. Restore the powers of your body by continuously giving your brain time for deep, restorative sleep.
References
Xie L, Kang H, Chen M et al. Sleep drives metabolite clearance from the adult brain. Science. 2013; 18: 342(6156).
Broussard JL, Kilkus JM, Delebecque F et al. Elevated ghrelin predicts food intake during experimental sleep restriction. Obesity. 2016; 24: 132-38.
Calvin AD, Carter TA, Macedo PG et al. Effects of experimental sleep restriction on caloric intake and activity energy expenditure. Chest. 2013; 144: 79-86.
Buxton OM, Cain SW, O’Connor SP et al. Adverse metabolic consequences in humans of prolonged sleep restriction combined with circadian disruption. Sci Trans Med. 2012; 4: 129-43.
Gangwisch JE, Malaspina D, Boden-Albala B and Heymsfield SB. Inadequate sleep as a risk factor for obesity: Analyses of the NHANES I. SLEEP. 2005: 1289-96.
St-Onge MP, McReynolds A, Trivedi Z et al. Sleep restriction leads to increased activation of brain regions sensitive to food stimuli. Am J Clin Nutr. 2012; 95; 818-24.
Fang Z, Spaeth AM, Ma N et al. Altered salience network connectivity predicts macronutrient intake after sleep deprivation. Scientific Reports. 2015; 5: 8215.
Killgore W, Schwab ZJ, Weber M. Daytime sleepiness affects prefrontal regulation of food intake. Neuroimage. 2013; 71: 216-23.
Lundahl A and Nelson T. Sleep and food intake: a mulitsytem review of mechanisms in children and adults. J Health Psych. 2016; 20(6): 794-805.