When a drug was used to stimulate the dorsal neostriatum — part of the brain that releases the chemical — the number of chocolates eaten more than doubled.
The study found that enkephalin binds to molecular ‘receptors’ in the brain, sensitive to opiate chemicals to reduce pain and produce pleasurable feelings.
Previous research mostly linked the dorsal neostriatum to movement, and recent work suggested it also plays a role in reward-driven behaviour.
Researcher and study leader Dr Alexandra DiFeliceantonio said the extraordinary findings showed comparisons between drug addicts and obese people.
“This (study) means that the brain has more extensive systems to make individuals over-consume rewards than previously thought,” she said.
“The same brain area 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 overconsumption and addiction in people,” DiFeliceantonio said.
The findings are published in Current Biology.