Tuesday, January 27, 2015

Sleep and Weight

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.

"Sleep woman" by Aweisenfels - Own work. Licensed under CC BY-SA 4.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Sleep_woman.jpg#mediaviewer/File:Sleep_woman.jpg


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. Emerging evidence suggests that the brain responds to food differently when you are sleep deprived compared to when you have adequate sleep. Getting adequate sleep may make it a little easier to adopt and adjust to lifestyle changes. Additionally, adequate sleep supports the body's circadian rhythm and natural hormone flux.



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



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