Many people believe that too much sleep can make them gain weight as they presume they feel dizzy and less active during sleep and immediately as the wake-up. However, science says otherwise, and it is our shared responsibility to know the basics science that surrounds sleep deprivation and obesity.
Introduction to sleep and types.
According to the Merriam-Webster dictionary, sleep is a natural temporary state of rest which portrays physical inactivity, unawareness of the surrounding environment, and the slowness of many human body functions. Being asleep brings about an inactive state and a type of hibernation whereby the individual’s eyes are usually closed, and the postural muscles of the person relaxed.
The American Academy of Sleep Medicine divided adult sleep into two stages called the non-rapid eye movement (NREM) and the rapid eye movement (REM) sleep. They further split NREM into deeper sleep stages called N1, N2, and N3 (or slow-wave sleep-SWS) sleep. REM is known as active sleep since the neural activity during this stage is similar to wakefulness, likewise metabolic, respiratory, and hemodynamic changes being more erratic at REM. It is often termed paradoxical sleep since our brain is highly active while we are asleep. REM usually occurs at 60-90minutes intervals and lasts for 5 to 30minutes. Our sleep period consists mostly of NREM, where SWS usually occurs in the first hours of sleep.
Looking at the effects of sleep and sleep deprivation on our body weight, we have the following cascade of reviews below.
Sleep Deprivation Increases Cravings.
Many people who spend fewer hours of sleep tend to consume some foodstuffs at late nights in particular, which may add up unnecessary calories to their body, and this is very true when high caloric foods or snacks are involved. Generally, when we spend more time awake, the probability for us to increase our number of meals increases, and so is the number of energy intake, which may exceed our energy expenditure, causing us to store extra calories and hence weight gain. This is confirmed through studies how a night of sleep restriction led to an increase in the consumption of food and a decrease in physical activity in healthy men.
Sleep and the Brain’s Frontal Lobe.
Most people who spend more time awake or barely sleep consume more calories because their brains tend to make unjust decisions. They become less resistant to snacks, slices of cakes, cookies, biscuits, sweets, etc. This was confirmed by the American Journal of Clinical Nutrition when they realized an increase in late snacking among people who spent more time awake.
The frontal lobe of the brain is actually is in charge of our inhibitory behavior and is responsible for this poor decision-making where less sleep actually causes a decrease in the metabolism of the frontal cortex, striatum, and thalamus. This explains why most people who spend fewer hours of sleep and wish to eat French fries, instead of saying “please don’t,” their frontal lobe would say “please have more taste” – because it is poorly metabolized due to sleep deprivation.
Less sleep is also known to increase blood levels of a lipid called endocannabinoid, which conditions the brain (as marijuana does) to make the consumption of food enjoyable, especially at night. However, this is restricted to some foods like candy, chips, biscuits, etc.
Sleep Deprivation, Ghrelin, and Appetite.
Ghrelin, popularly known as the hunger hormone secreted by the enteroendocrine cells of the stomach (or GI-tract), brings about the stimulation of appetite, production of blood glucose by the liver, and an increase in the storage of fat. Experts usually hold this hormone responsible for increasing the appetite and the consumption of food for individuals who had less sleep as the levels of ghrelin went up due to sleep deprivation. However, for those with good night sleep, their levels of ghrelin were low. Ghrelin usually exhibits its effects on the hypothalamic-pituitary axis and nearby regions of the brain vivifying appetite, the feelings of hunger, and increasing the consumption of more food by individuals.
On the other, leptin, an appetite-suppressing hormone secreted from the white adipocyte (adipose tissue) brings about the regulation of food intake and energy balance. The secretion of this hormone drops significantly for people with fewer hours of sleep. As a result, caloric deficit (a great parameter of weight loss) decreases as the individual’s appetite for food is not suppressed which may cause energy intake to exceed energy expenditure as he/ she becomes more vulnerable to food. Leptin usually acts on the central nervous system, particularly the hypothalamus, and is regulated by insulin-induced changes in adipocyte metabolism.
Sleep and Metabolism.
There is strong evidence that shortages of sleep and sleep disorders have some connections with metabolic and cardiovascular syndromes. This is usually seen in glucose metabolism. When we consume, our body’s pancreas secretes insulin, a hormone that regulates blood glucose levels. Sleep deprivation increases insulin resistance, reducing our body’s response to insulin and thus limiting the uptake of glucose by the cells.
Studies conducted by Donga et al., 2010 exposed that 4hrs of sleep greatly reduces insulin sensitivity (a decrease in the transportation of glucose from the blood to cells) which leads to the accumulation of excess glucose in the blood. More glucose in the blood causes the production of more insulin to regulate this blood glucose level. The production of more insulin in the body causes us to become hungrier as more people respond positively to this (by eating more food), unnecessary calorie intake will be registered which may be stored as fat and hence weight gain.
In a nutshell, insulin resistance is an antecedent and a facilitator of diabetes and overweight.
Sleep Deprivation lowers Basal or Resting Metabolic Rate.
The basal metabolic rate (BMR) and Resting Metabolic Rate (RMR), also called Resting Energy Expenditure (REE), literally mean the same thing. For more clarification, BMR is the energy needed to keep our body functioning at rest meanwhile RMR is the energy expenditure or the number of calories your body burns while at rest.
The RMR is the main way (close to 70%) our bodies burn calories. People who are subjected under some hours of sleep restriction (SR) usually experience a decrease in the RMR during the mornings, and this value is returned to baseline levels after sleep is recovered. A decline in RMR is probably due to a decrease in muscle mass still caused by sleep deprivation as the levels of cortisol spikes up. Generally, muscles are responsible for calories expenditure at rest.
Sleep and the HPA axis.
During sleep, most of the hypothalamic-pituitary-adrenocortical (HPA) hormones are suppressed. Sleep restriction or deep sleep like SWS (slow-wave sleep) inhibits the HPA axis, but the activation of the HPA axis may cause severe sleeplessness. Sleep disorders like insomnia and sleep deprivation have been reported to link with a 24hr surge of adrenocorticotropic hormone (ACTH) and the stress-response hormone (cortisol) secretion.
An increase in cortisol causes the body to store more fat and encourages the usage of muscles as energy. That is, sleep deprivation leads to fat gain and muscle loss.
Lipid Metabolism and Sleep.
Sleep alters the normal metabolism of lipids, glycerol, and free fatty acids (FFA), which can lead to the risk of obesity. When 15 participants’ blood was tested for lipid after being subjected to high-fat meal and sleep restriction of less than 5hrs for 4 continuous nights, results show that less sleep led to a decrease in lipid blood glucose level. “The lipids were not evaporated but were being stored,” Professor Orefu Buxton of the Pennsylvania State University reported.
Sleep and Physical Activity.
Having enough sleep causes you to be very active the next day, and you tend to do your day-to-day activities with ease and motivation. Many people who sleep less usually feel dizzy on their work desk, and their rate of physical activity drops. This is also evident as sleep deprivation was proven to lower physical activity among 15 healthy normal-weight men during the day.
Physical Activity as a Remedy to Poor Sleep.
Doing physical activity is likely to combat the implications of poor sleep. Physical activity reduces appetite by lowering the production of ghrelin and maximizing the secretion of the peptide YY, an endocrine hormone from the gut that induces satiety.
Exercise also improves insulin sensitivity, which is often impaired by sleep deprivation. This leads to an increase in the regulation of blood glucose level and thus no excessive secretion of insulin, which may cause future hunger and weight gain.
To practice healthy living, we should or must incorporate a healthy diet, exercise, and spend more hours (6-8hrs) of sleep as these are known to prevent us from the many metabolic disorders like diabetes, cardiovascular disease, and most specifically, obesity, which the WHO tagged as the pandemic of the 21st century.
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