The ‘munchies’ describes a sudden strong desire for food. The phrase, and the phenomenon, has long been associated with the use of marijuana, as after smoking pot people have a tendency to want to eat a lot, particularly junk food and sweets. But a new report has revealed that the munchies also appear after insufficient sleep, and researchers believe that they now know why.
The study was conducted as a collaboration between the University of Chicago’s Section of Endocrinology, Diabetes and Metabolism, the University of Chicago Medicine and the Medical College of Wisconsin, and was led by Erin Hanlon, PhD, research associate and assistant professor. They found that insufficient sleep raises the level of a specific substance that is a natural appetite stimulant. This, in addition to already-known shifts in the hormone levels of leptin and ghrelin, provide more evidence as to why lack of sleep contributes to weight gain and obesity. According to Hanlon, “Past experimental studies show that sleep restriction increases hunger and appetite. The mechanism for overeating after inadequate sleep may be an elevation in this endocannabinoid molecule, called 2-arachidonoylglycerol, or 2-AG.”
The group studied nine subjects, and had each spend six nights sleeping in a sleep lab. The group was then asked to do the same a month later. They were randomly assigned to sleeping periods of 11 pm to 7:30 am (equaling a normal sleep quantity of 8.5 hours) during one of their sessions and from 1 am to 5:30 am (partial sleep restriction of just 4.5 hours in bed). While they were awake they were each assigned a specific caloric intake based on their height and weight and were restricted to that number of calories. The group was made up of healthy young adults with an average age of 23 years old.
After submitting the subjects to these sleep conditions, blood was drawn from each of them at one-hour intervals for the next twenty-four hours. The samples were analyzed using a highly accurate blood assay and tested for the presence and levels of 2-AG, a component of the endocannabinoid system. The endocannabinoid system is found throughout the body and signals enjoyment in eating in much the same way that cannabinoids in marijuana produce a sensation of pleasure from eating. What the researchers found was that the levels were lowest halfway through the sleep cycle and highest at what is normally considered lunch time – the early afternoon. This makes sense, as it is “when the pleasurable properties of food would be most beneficial,” according to Hanlon. Interestingly, those levels were higher in the study participants when they had been sleep deprived, suggesting that increased hunger and pleasure in eating occur after sleep restriction as a result of increases in circulating 2-AG.
With physicians becoming increasingly concerned about the obesity epidemic, this information may prove helpful in recommending that patients with weight problems get more sleep. Hanlon says, “These findings are highly relevant to millions of individuals who are at an increased risk of obesity and its health consequences because of chronic short sleep or sleep disruption.”