Ever wondered what makes us crave for a doughnut or that bar of chocolate in the afternoon after a night of binge watching Netflix until 3 am or after a night out with friends? A new study shows that losing sleep could result in an increased appetite and weight gain.
What is Sleep?
Sleep is a state of rest for the mind and body. It is a behavioral state characterized by the suspension of bodily functions, inhibition of the voluntary muscles and reduced but reversible reaction to external stimuli. Sadly, many of us tend to think of sleep as a passive part of our daily life. On the contrary, sleep contributes significantly to the life sustaining activities of the organisms. But, little do we realize that sleep loss can have poor health outcomes and even have an effect on the lifespan. Sleep-deprived rats live for only 5 weeks compared to their average lifespan of 2-3 years. Sleep loss has also been linked to detrimental effects on the immune system by increasing the levels of pro-inflammatory cytokines.
Link Between Sleep Deprivation and Obesity
More recently, there has been a surge of research on sleep deprivation being linked to an increased risk of obesity and other gastrointestinal diseases. Obesity is a condition of energy imbalance, which arises due to the consumption of more calories than required for the daily needs. According to the Center for Disease Control (CDC), about 34% of U.S. adults and 17% of children are obese. Obesity is a serious problem as it predisposes an individual to a wide array of comorbidities such as diabetes, cardiovascular diseases and even cancer. A large part of treatment for obesity is based on lifestyle modifications by keeping a check on the food intake and being physically active.
Researchers at University of Chicago have shown that insufficient sleep puts an individual at risk of weight gain by the stimulation of hunger and food intake through the activation of the endocannabinoid system, which is involved in eating for pleasure and not to fulfill the caloric need. It is the same system that mediates the effect of cannabis or marijuana. Endocannabinoids (eCB) are naturally synthesized lipids in the body that are involved in the regulation of appetite, mood, and pain management.
The Study
The group, led by Dr. Eve Van Cauter, conducted a randomized crossover study by comparing two groups of healthy young adults who were allowed to sleep for 8.5 hours (normal sleep) or 4.5 hours (sleep deprived) for 4 nights. They then measured the mean serum concentration for an eCB, 2-arachidonolglycerol (2-AG). The sleep-deprived group had elevated circulating levels of 2-AG with an extended peak in the concentration in the afternoon compared to the normal sleep group. Additionally, they also found that the ratio of the hunger stimulating hormone (ghrelin) vs the satiety inducing hormone (leptin) was increased in sleep-deprived individuals.
Subsequently, the sleep-deprived individuals scored high when questioned about their desire to eat, how hungry they felt and their global appetite despite being full compared to the normal sleep group. The sleep-restricted participants were also less capable of controlling their temptation to consume the palatable snacks even after having ingested 90% of their daily calories 1-2 hours earlier whereas the normal sleep group showed a decrease in the subsequent snack intake after the ingestion of a big meal.
This research suggested that sleep loss, which results in higher levels of eCB in the afternoon, enhances our desire for pleasurable eating and consistent sleep deprivation could lead to excessive food intake eventually resulting in weight gain.
A person can be predisposed to developing obesity by a lot of factors such as genetics and family history, environment, hormonal imbalance, inactive lifestyle, age and emotional factors. While we can’t control our genetic makeup, a simple lifestyle modification such as instilling a healthy sleep schedule could help in keeping obesity at bay.
References:
http://www.ncbi.nlm.nih.gov/pubmed/26612385
http://www.ncbi.nlm.nih.gov/pubmed/27134599
http://www.ninds.nih.gov/disorders/brain_basics/understanding_sleep.htm
https://www.cdc.gov/obesity/data/index.html
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