McMenamin’s pub serves a chocolate milkshake containing the restaurant’s signature stout beer, a combination that may seem counterintuitive when it comes to taste. However, a recent study suggests it probably makes sense to the reward center of the drinker’s brain.
The study, led by Oregon Research Institute member Eric Stice and conducted at the University’s Lewis Imaging Center, linked the brain’s response to food in overweight and obese people with an addict’s response to drugs.
Researchers in the study gave chocolate milkshakes to the study participants, women aged 14 to 22 years old, while the researchers took brain images. The study recorded the response in the striatum, the brain’s largest reward center, and compared the responses of lean, overweight and obese subjects.
The striata in overweight and obese people showed less reward response to the milkshakes than did the striata in lean people. Additionally, subjects who had the “DRD2” gene, which reduces dopamine production, had the least response of all. This led researchers to determine that the response to the milkshake was probably caused by dopamine, a neurotransmitter that is directly linked to reward sensations.
Overweight and obese subjects anticipated more reward from the milkshake than lean subjects did, brain scans showed. This discrepancy between anticipated reward and received reward, Stice said, is a “hugely strong parallel” with drug addiction.
When people use drugs, they anticipate a dopamine reward, just like subjects’ brains expect one from the milkshakes. However, when a person uses a drug often, the brain issues less dopamine. The person uses more and more of the drug to get the reward they anticipate.
Stice thinks the same thing happens in overweight and obese individuals. Overeating initially reduces the brain’s response to food and causes people to overeat more, he said.
The study also followed some subjects over a year-long period, and found that individuals with a low brain response to food gained more weight over time, which supports his idea that the lack of response causes people to overeat.
University junior Stephanie Turco said she considers eating a necessity and never imagined it could become an addiction. However, she said, “Food can make you feel better,” and admitted to mashed potatoes as her comfort food.
Stice said mashed potatoes and pizza make sense as comfort foods. Carbohydrates and fats elicit a large dopamine response, making people feel better. Mashed potatoes and gummy bears are surprisingly similar in the way the brain interprets them, he said.
University sophomore Joe McRae found the idea of food addiction less surprising. Just like with drug abuse, he said, if you ate something all the time, you’d get less of a response and probably keep eating to get it back.
The link between the brain’s response to food is really conjecture at this point, Stice said. Some colleagues don’t agree with him and suggest overeating does not trigger a lower response, but that a low response causes the overeating. However, Stice is confident he is on to something.
“It’s a very reasonable working hypothesis,” he said.
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