The researchers believe that sleeping less than the optimal number of hours alters brain chemicals in such a way that individuals are unable to resist snacks, even when full.
While the link with poor sleep to increased appetite - particularly for sweet and salty foods - has been established, these findings identify a specific region of the brain that is impaired when controlling appetite and food intake following a sleepless night.
Obesity and the propensity to gain weight has long been a topic associated with professions that involved disrupted sleep patterns and shift work.
It is thought that several pathways could be involved in this weight gain including increased food intake, decreased energy expenditure, and changes in levels of appetite-regulating hormones, such as leptin and ghrelin.
Researchers from the universities of Brussels and Chicago devised a randomised crossover study that compared 4 nights of normal sleep duration (8.5 hours) and restricted periods of sleep (4.5 hours).
They recruited 14 men and women in their twenties to participate in the study. Clinical conditions during this period included the consumption of identical meals, which were served at 9am, 2pm and 7pm.
On the fourth night of each stage of the trial, the subjects were given a choice of unhealthy snacks. Those who experienced a lack of sleep reported strong cravings for these snacks, which were felt most strongly in the late afternoon and early evening.
The consumption of these snacks took place even though the volunteers had eaten food that contained 90% of their recommended daily calories two hours earlier.
In general, the researchers observed a consumption of 300 snack-related calories, much more than were required to function during the extra hours the participants were awake.
The study aimed to discover the role of the endocannabinoid (eCB) system in the controlling appetite and food intake, in the aftermath of sleep deprivation.
Lead researcher, Erin Hanlon found that sleep deprived individuals had a higher level of endocannabinoid 2-AG, a chemical compound that increases the pleasant feelings of food, especially sweet or salty high-fat foods.
In those who gained the optimal levels of sleep endocannabinoid 2-AG levels increased in the morning, peaked around midday, and decreased later in the day. But in the sleep-deprived, levels rose 33% higher, peaked at 2pm, and remained high until 9pm.
“This may boost and prolong the pleasure people get from snacking, putting them more at risk of weight gain,” Hanlon said in the study.
“The early afternoon drive for hedonic eating may be stronger and last longer in a state of sleep debt.”
Link to Leptin
The eCB is a collection of endocannabinoid receptors located in the human brain and central nervous system. The eCB has been implicated in a variety of physiological processes including appetite, pain-sensation, mood, and memory, and in mediating the psychoactive effects of cannabis.
Previous studies provide strong evidence for the role of the eCB system in food-seeking behaviour. For example, endocannabinoids have been shown to work together to regulate hunger. As far back as 1998, research has proved the amount of endocannabinoids produced is inversely correlated with the amount of leptin in the blood.
More recently, a related study found that endocannabinoids affect taste perception in taste cells while the hormone leptin decreased the strength of this same response. Leptin, along with ghrelin has already shown their effect during sleep deprivation and the development of obesity.
Published online ahead of print, http://dx.doi.org/10.5665/sleep.5546
“Sleep Restriction Enhances the Daily Rhythm of Circulating Levels of Endocannabinoid 2-Arachidonoylglycerol.”
Authors: Erin C. Hanlon; Esra Tasali; Rachel Leproult; Kara L. Stuhr; Elizabeth Doncheck; Harriet de Wit; Cecilia J. Hillard; Eve Van Cauter.