How many hours did you sleep last night? Did you wake up
feeling rested? Many adults (as well as teens) stay up late, struggle to fall
asleep and wake up tired. Sleep is a frequently overlooked component of health
and wellness. It affects how you eat, your body weight and your activity level. Regular
and adequate sleep helps you feel better and improves your ability to achieve your
health related goals.
How much sleep is enough?
According to the National Heart Lung and Blood Institute (National Heart Lung and Blood Institute (NHLBI)),
7-19% of adults in the United States said that they do not get enough sleep. Inadequate
sleep is associated with a greater risk of obesity as well as type 2 diabetes, high
blood pressure, stroke and heart disease. In the United States, 34.9% of adults
are obese (CDC obesity statistics).
Clearly, sleep deprivation alone does not account for the obesity rate in the United
States. However, not getting enough sleep may contribute to weight gain and to
slow (and frustrating) weight loss for some people. How much sleep a person
needs is individual, however, there are guidelines (table 1).
Table 1. Recommended Hours of Sleep (NHLBI - How Much Sleep )
Group
|
Recommended hours
of sleep
|
Adults
|
7-8 (night)
|
Teens
|
9-10
(night)
|
School aged children
|
At least 10 (night)
|
Preschool aged children
|
11-12
(day)
|
Newborns
|
16-18 (day)
|
These guidelines
apply to everyone and you can figure out how much sleep you need by keeping a
sleep diary. Record
* when you go to bed, how long you sleep and make note
of any naps you may take,
* how you feel in the morning when first wake up,
* how you feel throughout the day,
* the foods you eat during the day.
Keep your sleep diary for a couple of weeks to collect
enough information to reflect your lifestyle. Use the guidelines in table 1 as
a reference. For adults, 7-8 hours of sleep a night is recommended. Do you fall
asleep when you do not intend to (watching TV, at a movie, in a meeting,
sitting in class, in the car while stuck in traffic)? If so, you
are not getting enough sleep or the quality of your sleep is not adequate.
Some people are in challenging situations. The reality is
that someone with very young children who do not yet sleep through the night is
not going to get that much sleep. Shift workers face challenges, especially
when overnight shift work is occasional. You do what you can. Let yourself nap
if sleeping through the night is truly not an option. However, someone who gets
less sleep because of lifestyle choices and who wants to make lifestyle changes
that include weight reduction and physical activity can find ways to
incorporate more sleep and a regular sleep schedule. Depriving yourself of
sleep and getting too much sleep are both associated with negative health
consequences.
Leptin and Ghrelin
Leptin:
Energy from nutrients enters the body from carbohydrates,
proteins, and fats. First, the body uses the energy for fuel. Once it has used
what is needed, it stores energy. Most of the excess energy from the food you eat is
stored as fat in fat cells. When the fat cells (called adipocytes) secrete a hormone called leptin. Leptin travels to the hypothalamus and signals to the brain
that you have had enough to eat. Leptin is thought of as the fullness hormone.
Leptin is part of the body’s appetite suppressant system. The body naturally secretes
more leptin at night. This makes sense because at night we are getting ready
for bed. When we sleep, we do not eat. There is no need to be hungry – leptin hormone
suppresses our appetite.
Ghrelin:
The stomach produces a hormone called ghrelin. Ghrelin travels from the stomach to the hypothalamus where it signals to the brain that it is time to eat. Ghrelin is thought of as the
opposite of leptin in terms of how it affects food intake. When you are hungry,
your stomach growls (“grrr for ghrelin” – at least that is how I remember it).
Sleep, leptin, ghrelin and weight loss
The body has an internal 24-hour-ish clock that is the
circadian rhythm. Some of our hormones rise and fall with that cycle.
Certain environmental cues trigger the production of some chemicals. As the sun
sets and darkness falls, the body produces melatonin (produced by the pineal gland).
Melatonin gradually increases throughout night leading to sleep. Levels
gradually decrease overnight and throughout the morning. Things like artificial
lights, TV screens, computer screens, etc. can alter melatonin. Cortisol is a
hormone produced by the adrenal glands. As morning breaks and the sun rises, so do
cortisol levels. Cortisol levels are highest in the morning at lowest late at
night. These fluctuations are normal and healthy.
Scientists speculate that not getting enough sleep
contributes to the following that together contribute to increased weight
gain, particularly fat gain, and may inhibit weight loss.
* Not getting enough sleep is believed to increase
appetite partially because the body produces more ghrelin (hunger) and less
leptin (appetite suppressant) (Morselli, Leproult, Balbo, & Spiegel, 2010; Sharma & Kavuru,
2010; Shlisky et al., 2012).
* Because there is more time and opportunity,
people tend to eat more when they sacrifice sleep for wakeful hours (Morselli et al., 2010; Sharma & Kavuru, 2010; Shlisky et al., 2012).
* In small sleep studies where participants got both normal sleep and short amounts of sleep, researchers demonstrated with functional MRIs that the brain responds differently to images
of unhealthy foods and healthy foods and that this affects how people make food
choices when they are sleep deprived (Greer, Goldstein, & Walker, 2013; St-Onge, Wolfe, Sy, Shechter, &
Hirsch, 2014). People who got anywhere from no sleep to 4 hours of sleep made similar high-calorie, high-carbohydrate and high-fat food choices.
* Increased fatigue which leads to decreased
physical activity and participation in more sedentary activities. The body may
also use less energy at rest during times of sleep deprivation (Shlisky et al., 2012)
* Finally, there may be a shift in how the body
uses and stores energy. Scientists believe that the body becomes less
responsive to insulin, uses glucose less efficiently, and is more likely to
store fat. Increased ghrelin at night and increased cortisol at night may
contribute to this. In normal conditions, cortisol is highest in the morning
when you wake up, fluctuates throughout the day, and is lowest at midnight (Morselli et al., 2010; Sharma & Kavuru, 2010; Shlisky et al., 2012).
If you are working to reduce weight, it is important to examine your sleep quality and habits. The quantity and quality of
your sleep matters. A comprehensive approach to weight-loss and management
should address sleep.
Final Thoughts
If you are concerned that you have a medical condition that
impairs your ability to fall asleep or stay asleep, discuss this with your
health care provider. Medical conditions, like obstructive sleep apnea, affect
sleep quality and require medical attention. This link (NHLBI-How to) provides a list of
questions and things to think about when discussing sleep concerns with your
health care provider.
The functional MRI studies I read were only published within
the past few years. There is much science does not understand about how the brain
responds to chronic sleep deprivation as well as the interplay between sleep
deprivation and hormones. There is an entire universe of
microorganisms living in your gut that science has only begun to understand.
In time we will find out how microorganisms contribute to the network
of communication between the gut, fat cells and brain. At this time, we know
that people who get too little or too much sleep have a greater risk of obesity,
type 2 diabetes, heart disease, high blood pressure, and stroke. Sleep is a
modifiable risk factor for most people. There is a tendency to view sleep as a
luxury or something we “get to do” at the end of the day. If you are working on
health related goals like weight reduction, take a look at your sleep. Not
getting enough sleep, even for just a couple of days, is counter-productive.
Articles that may be
of interest
- Scientific American: How slight sleep deprivation could add extra pounds (10/24/2012)
- Science Daily: Sleep deprivation linked to junk food (8/6/2013)
References
Greer, S. M., Goldstein,
A. N., & Walker, M. P. (2013). The impact of sleep deprivation on food
desire in the human brain. Nat Commun, 4,
2259. doi: 10.1038/ncomms3259
Morselli, L., Leproult, R., Balbo, M., &
Spiegel, K. (2010). Role of sleep duration in the regulation of glucose
metabolism and appetite. Best Pract Res
Clin Endocrinol Metab, 24(5), 687-702. doi: 10.1016/j.beem.2010.07.005
Sharma, S., & Kavuru, M. (2010). Sleep and
metabolism: an overview. Int J
Endocrinol, 2010. doi: 10.1155/2010/270832
Shlisky, J. D., Hartman, T. J., Kris-Etherton,
P. M., Rogers, C. J., Sharkey, N. A., & Nickols-Richardson, S. M. (2012).
Partial sleep deprivation and energy balance in adults: an emerging issue for
consideration by dietetics practitioners. J
Acad Nutr Diet, 112(11), 1785-1797. doi: 10.1016/j.jand.2012.07.032
St-Onge, M. P., Wolfe, S., Sy, M., Shechter, A.,
& Hirsch, J. (2014). Sleep restriction increases the neuronal response to
unhealthy food in normal-weight individuals. Int J Obes (Lond), 38(3), 411-416. doi: 10.1038/ijo.2013.114
