Science may finally have an explanation for those chocolate cravings.
US researchers discovered part of the brain releases a natural opium-like chemical when chocolate is consumed.
The study found the drug-like chemical enkephalin soared in rats when part of the brain called the neostriatum was artificially stimulated.
The animals gorged themselves on more than twice the amount of M&M chocolates when a drug was delivered straight to the brain, according to the research published online in the journal Current Biology.
"It may be one reason why over-consumption is a problem," said Alexandra DiFeliceantonio from the University of Michigan.
"The same brain area we tested here is active when obese people see foods and when drug addicts see drug scenes.
"It seems likely that our enkephalin findings in rats mean that this neurotransmitter may drive some forms of over-consumption and addiction in people."
The brain chemicals increased the rat's desire and impulse to eat the candy, rather than the enkephalins making the animals like the chocolate more, the study found.