Sleep Deficit Can Cause Obesity
A good night’s sleep is one of the pre-requisites to good health. There is growing evidence that people who get too little sleep have a higher risk of weight gain and obesity than people who get seven to eight hours of sleep a night.
The term - lack of sleep - generally refers to an insufficient amount of sleep for optimal functioning. The ideal amount of sleep per night varies from one person to another. We need to keep in mind that healthy sleep includes dimensions other than sleep quantity such as sleep quality, timing, architecture, consistency and continuity.
National Sleep Foundation recommends the requirements of sleep for adults as mentioned below:
- Younger adults (18-25): Sleep range is 7-9 hours (new age category)
- Adults (26-64): Sleep range did not change and remains 7-9 hours
- Older adults (65+): Sleep range is 7-8 hours (new age category)
The sleep requirements for infants, children and teenagers are more. However, there are few people who require lesser sleep for optimal functioning.
Mechanisms responsible for obesity due to sleep deficit -
The following mechanisms are understood to play important role:
It deregulates hunger hormones - Lack of sleep may disrupt a number of hormones that affect our drive to eat. Hormone leptin, which is secreted by fat cells, says the body has plenty of energy in reserves and the brain should produce the feeling of fullness, whereas, ghrelin a hormone secreted by the digestive system tells the brain to make the person hungry, when there is little food in the stomach
Thus, leptin and ghrelin are part of the body’s weight homeostasis mechanism. They regulate the body’s energy balance, making the brain feel hungry or full. Chronic insomnia affects the level of ghrelin, but not the level of leptin.
It increases levels of orexin - Even after short sleep of one night, the area of the brain that senses appetite is more activated than usual. The neurotransmitter – orexin - discovered in recent decades but still not totally understood, appears to play a part in both keeping us awake and alert. The orexin system becomes more activated in times of sleep deprivation and gives us the tenacity to continue to look for food. People with narcolepsy have a deficiency in the orexin-producing part of the brain.
It disturbs carbohydrate metabolism - Sleep loss can affect the basic metabolic functions of storing carbohydrates and regulating hormones. A reduction of sleep from eight hours to four hours produces changes in glucose tolerance and endocrine function. The researchers have found that changes that occur in glucose metabolism resemble that of type-2 diabetes patients. Sleep deprived persons took 40% longer than normal to regulate blood sugar levels after a high-carbohydrate meal. The body's response to insulin decreases by 30%.
It lowers TSH and increases cortisol - Sleep deprivation also alters the productions of hormones, lowering the secretion of thyroid stimulating hormone and increasing blood levels of cortisol. They all contribute to overweight and obesity over a period of time.
It reduces inhibitory control - The researchers have found differences of brain activity in sleep deprived people's response to food. Their study revealed increased activation in an area of brain called insular cortex, which regulates pleasure-seeking behaviors. So, sleep deprived persons lose their inhibitory control over impulsiveness to reach for high calorie foods.
It offers more opportunities to eat - Less time spent sleeping also means more time and opportunities for eating.
It promotes additional eating - Lack of sleep has been shown to increase snacking, the number of meals eaten per day and the preference for energy-dense foods. Increased food intake associated with a lack of sleep can also be seen as a normal physiological adaptation to provide energy needed to sustain additional wakefulness.
It promotes physical inactivity - Sleep loss generally leads to a general feeling of fatigue, which can make us feel less inclined to want to do physical activity.
The bottom line –
It has been found conclusively that a chronic sleep deficit can make us overweight and obese. The research shows that lack of sleep can impact appetite regulation and impair glucose metabolism. Besides these, sleep deprivation can make us overweight and obese in some other ways too. Thus, we cannot overlook the importance of adequate sleep daily in maintaining ideal weight, for which it is very important to develop good sleep habits.
- Wiley-Blackwell. "Lack of sleep is linked to obesity, new evidence shows." ScienceDaily. ScienceDaily, 17April 2012.
- Sleep Med Clin. 2007 Jun; 2(2):187-197.