The older we get, the less we crave sweet foods. In general this is how the science goes, partly because with age comes fewer dopamine receptors in the brain, and those dopamine receptors play a role in how our brains gauge pleasure. But according to a new study, the science seems to veer off course in people who are obese.
Researchers from the Washington University School of Medicine in St. Louis recruited a combination of healthy weight and obese individuals between the ages of 20 and 40. Participants were asked to drink sugar-sweetened beverages to determine their preferred sweetness level, while PET scans measured activity in the brain’s pleasure center.
In the healthy weight participants, researchers saw what they expected: an association between age, dopamine receptors and a preference for sweets. However, this was not the case in the obese individuals, who didn’t follow the normal pattern. The findings point to a possible abnormality in the brain’s reward center that may contribute to obesity risk.
Study authors speculate the difference may be tied to certain metabolic markers linked to obesity, such as insulin resistance. However, they point out that although there were some early signs of high blood sugar in some of the obese subjects, none had been diagnosed with diabetes.
“What’s clear is that extra body fat can exert effects not only in how we metabolize food but how our brains perceive rewards when we eat that food, particularly when it’s something sweet,” said study co-author Tamara Hershey, PhD. This study and others like it may one day help scientists better understand the biological mechanisms that lead to obesity.