The researchers
found that when healthy, lean, young adults received only 4.5 hours of sleep a
night, they had higher daytime circulating, or blood, levels of a molecule that
controls the pleasurable aspects of eating, compared with when they slept 8.5
hours.
"The mechanism
for overeating after inadequate sleep may be an elevation in this endocannabinoid
molecule, called 2-arachidonoylglycerol, or 2-AG.
studied nine
subjects with an average age of 23 years. The subjects spent six nights in a
sleep lab and then another six nights there at least a month later. In a random
order, the subjects were allowed to sleep from 11 p.m. to 7:30 a.m.
("normal sleep -- 8.5 hours in bed") during one testing period and
from 1 to 5:30 a.m. ("partial sleep restriction -- 4.5 hours in bed")
during the other testing period. During waking hours, the subjects ate a
controlled number of calories based on their height and weight.After the second
night of each sleep condition, the researchers took blood samples from the
subjects at one-hour intervals for 24 hours. Using a highly accurate laboratory
assay, they analyzed the samples for 2-AG, a component of the endocannabinoid
system. Found throughout the body, this system plays an important role in the
signaling of rewarding events and one's enjoyment of eating, similar to the
cannabinoids in marijuana, Hanlon said.Levels of 2-AG levels were the lowest
halfway through sleep and the highest in the early afternoon, "when the
pleasurable properties of food would be most beneficial," Hanlon said. She
reported that the afternoon peak of 2-AG was even higher when the study participants
had partial sleep restriction than when they had normal sleep.
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