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Obesity linked to abnormal reward response to sugary foods

(Online News): An unhealthy diet is considered a key contributor to obesity. When it comes to cravings for sweet treats, however, impairments in the brain’s reward system might be to blame.

Researchers say the reward system in the brains of obese individuals appears to be impaired in response to sweet foods.
In a new study published in the journal Diabetes, researchers found age and receptor levels of the reward-associated chemical dopamine influence preference for sweet foods among people of a healthy weight, but not for people who are obese.

First author M. Yanina Pepino, Ph.D., of the Washington University School of Medicine, and colleagues reached their findings by enrolling 44 adults aged 20-40 years.

A total of 24 of the participants were obese – defined in the study as having a body mass index (BMI) of 30 or higher – while 20 were a healthy weight.

The researchers asked the participants to consume a number of drinks, each containing different sugar contents, and rate which ones they preferred.

Subjects then underwent positron emission tomography (PET) scans, which allowed the researchers to assess dopamine receptor levels in each subject’s brain.

Dopamine is a neurotransmitter – a chemical that enables communication between nerve cells – that regulates the reward and pleasure centers of the brain.

On analyzing the brains of the healthy-weight participants, the researchers found that younger age and fewer dopamine receptors were associated with a greater preference for sugar.

“We found disparities in preference for sweets between individuals, and we also found individual variations in dopamine receptors – some people have high levels and some low,” explains study co-author Tamara Hershey, Ph.D., a professor of psychiatry, neurology, and radiology at Washington.

“But when we looked at how those things go together, the general trend in people of normal weight was that having fewer dopamine receptors was associated with a higher preference for sweets.”

However, this was not the case in the brains of the obese participants, suggesting that the brains of obese individuals are altered in some way to influence preference for sweet foods.