Feeling tired, hungry seem to go together and chemical 2-AG may be why Feeling tired, hungry seem to go together and chemical 2-AG may be why. A Chinese migrant worker tries to avoid the midday heat by sleeping on shovels in Beijing on July 11, 2012. CHICAGO, Aug. 30 (UPI) -- A U.S. researcher says feeling tired and feeling hungry seem to go together and the chemical 2-AG may be the reason why. Erin Hanlon of the University of Chicago said the study involved nine people who spent 13 nights in a sleep lab, gave blood for analysis and ate a controlled number of calories. Hanlon examined the chemical 2-AG, which is part of a system that has a role in enjoyment, such as enjoying eating. She said when people were allowed fewer minutes of sleep, their levels of 2-AG were higher in mid-afternoon -- just in time for the mid-afternoon snack. "Individuals need to think of adequate sleep as an important aspect of maintaining good health, and not just as a by-product of the day," Hanlon said in a statement. The study was presented at a meeting of The Endocrine Society.