Sleep? Not me!
The US is a country of sleep-deprived people. Data from the National Health Interview Survey revealed that nearly 30% of adults reported an average of 6 or fewer hours of sleep per day in 2005-2007 (as opposed to the recommended 8 hours). The US is also a nation of people who are increasingly overweight or obese. Might the two be connected?
Sleep is more than rest
Sleep is downtime. But, more importantly, it is also a time for repair of neurons. Good sleep helps immunity, and is important for learning, forming memories, and maintaining a healthy immune system.
An increasing number of health problems have been linked to poor or insufficient sleep, including links between poor sleep and weight problems.
A large body of research suggests that sleep-deprivation can lead to obesity. A previous article from our archives outlines many of the mechanisms involved, and it can be reviewed here … http://goo.gl/2zvrn4.
Reward, addiction, food, and the brain
Researchers have started focusing on the nature and mechanism of reward and the involvement of specific brain centers in certain behavior patterns, including food intake, and even drug addiction.
The mesolimbic dopamine system is the most important reward pathway in the brain, leading to the transfer of dopamine from one part of the brain to another. This system regulates the formation of habits.
The Triune brain of mammals: 3 in 1!
Proposed by Paul MacLean, this is a simplified, some say oversimplified, way of looking at the brain from the evolutionary point of view. It means three brains in one. There is the oldest part of the brain, or reptilian brain, which is involved in the processes necessary for survival, such as breathing, heart rate, balance, body temperature, and the like. It is basically the brainstem.
The limbic system, or the paleomammalian brain, is the second oldest part of the brain. Limbus refers to a border. This limbic system is the collective name given to a set of structures surrounding the limit between the brainstem and the cerebral hemispheres. This is where the cerebral cortex meets the structures beneath it.
Traditionally, the limbic system is felt to include the hypothalamus, the amygdala, the hippocampus, and other surrounding areas. It is responsible for emotions, memories, and value judgments.
The mesolimbic system is the more central part of the limbic system. It connects the ventral tegmental area in the midbrain to the nucleus accumbens. Functioning as a reward pathway, this system is involved significantly in most known forms of addiction.
The neocortex is the outer part of the brain and is mostly made up of two large cerebral hemispheres, which deal with language, consciousness, abstract thought, imagination, stimulus analysis, and motor control. It is the youngest part of the brain.
What about the endocannabinoid system?
This is triggered in people who smoke marijuana.
This system is also implicated in the reward mechanisms involving the brain and its pathways. It mediates the psychological effects of cannabis, and is therefore also called the body’s own cannabinoid system. It is made up of lipids (or fats) and their receptors.
There are two main endocannabinoid receptors, called CB1and CB2. The main lipids which are part of this system, and which act on the receptors already mentioned, are 2-AG and CBD.
This system appears to be involved in reward-driven or pleasure eating.
A recent study out of the University of Chicago found that people who were sleep-deprived had a greater activation of their endocannabinoid system.
People who had a full night’s sleep, in this study, ate 600 calories in early evening snacks. However, people who were sleep-deprived consumed almost 1000 calories in such snacks, and ate twice as much fat.
Consuming 400 extra calories a day regularly can lead to up to 40 lbs of weight gain in a year!
This endocannabinoid can be measured in the bloodstream. Average levels of this lipid were similar in the people who had shorter-duration sleep (4.5 hours) versus normal-duration sleep (8.5 hours) in the Chicago study. However, the peak levels were higher in sleep-deprived people, and this peak occurred later in the day. Interestingly, the sleep-deprived individuals felt hungrier at the time of the peak 2-AG levels, and reported a stronger desire to eat at those times.
So what’s the link?
Several studies have investigated the links between sleep, food intake, and obesity.
There is evidence that sleep deprivation leads to an increase in the blood levels of ghrelin, a hormone which causes an increase in hunger, and a reduction in leptin, which suppresses hunger. The net effect is an increase in food intake in people who do not get sufficient sleep.
It can be argued that if you do not get enough sleep, you are obviously awake for longer, and thus your energy expenditure will be higher, just because you are awake, and probably engaged in some activity or the other. However, the increase in food intake in sleep-deprived people over-rides their excess energy expenditure. Thus the weight gain we see with sleep deprivation.
BMR and sleep deprivation
A study performed by researchers at the University of Pennsylvania School of Medicine in 2015 revealed that people who were sleep deprived for five days had a lower Basal Metabolic Rate (BMR) in the morning compared with their BMR after a night of normal sleep. Extrapolating this, the researchers found that people who were sleep deprived burned 42 calories less the next morning, compared with people who had a normal duration of sleep.
Sleep deprived individuals tend to have a greater craving for salty food, followed by sweet foods. This is also likely to contribute to their weight gain. Additionally, sleep deprivation seems to lead people to eat more snacks, rather than larger meals.
Diet and sleep deprivation
At least one study has found that sleep deprived people who go on a diet end up losing more lean body mass rather than fat mass.
Food and sleep quality
How well you sleep affects what you eat, and how much. But, interestingly, what you eat during the day can also affect how well you sleep that night.
People who eat more sugar during the day tend to wake up more in the middle of the night. Higher fiber consumption during the day is associated with more slow-wave sleep, which is deep sleep, felt to be important for new memories.
By contrast, a higher intake of saturated fat during the day is associated with less slow-wave sleep.
- Sleep and body weight are intricately related.
- There is a clear relationship between sleep deprivation and weight gain.
- The mechanisms are not entirely clear, but appear to be related to changes in ghrelin and leptin levels, as well as stimulation of the endocannabinoid system.
- The endocannabinoid system is a reward system involving the brain, and appears to encourage snacking and higher caloric intake.
- Sleep deprivation tends to promote intake of salty and sugary foods.
- Food choices during the day (fiber, sugar, saturated fat) can alter sleep quality at night.
- Sleep deprivation is also associated with many other significant health problems.
- Many Americans (and likely those in other parts of the world as well) are not getting the recommended amount of sleep. Healthcare providers need to make a concerted effort to promote healthy and adequate sleep in the population at large.