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Sweet preferences & obesity

As young people reach adulthood, their preferences for sweet foods typically decline. But for people with obesity, new research suggests that the drop off may not be as steep and that the brain’s reward system is operating differently in obese people than in thinner people, which may play a role in this phenomenon.

AS WE GET OLDER, WE TEND TO HAVE LESS OF A PREFERENCE FOR SWEET THINGS. DURING THAT SAME TIME IN LIFE, THE NUMBER OF A PARTICULAR TYPE OF DOPAMINE RECEPTOR IN OUR BRAINS BEGINS TO DECLINE, AND THERE IS A STRONG RELATIONSHIP BETWEEN RECEPTORS, AGE AND SWEET TASTE PREFERENCES IN PEOPLE WHO DON’T HAVE OBESITY. BUT SCIENTISTS AT WASHINGTON UNIVERSITY SCHOOL OF MEDICINE IN ST. LOUIS HAVE FOUND THAT THINGS DON’T WORK THAT WAY IN PEOPLE WHO DO HAVE OBESITY. JIM DRYDEN HAS THE STORY…

WHEN WE EAT, OUR BRAINS RELEASE CHEMICALS THAT MAKE US FEEL GOOD, AND WHEN WE EAT SOMETHING REALLY GOOD, THE SAME THING HAPPENS, ONLY MORESO. A BRAIN CHEMICAL CALLED DOPAMINE IS WHAT MAKES US FEEL GOOD, AND TO MEASURE DOPAMINE RELEASE IN RESPONSE TO FOOD, SCIENTISTS OFTEN MEASURE OUR REACTION TO SWEET THINGS BECAUSE EVERYONE TENDS TO LIKE SWEETS, WASHINGTON UNIVERSITY NUTRITION RESEARCHER YANINA PEPINO SAYS AS PEOPLE GET OLDER, A COUPLE OF THINGS HAPPEN. WE TEND TO HAVE LESS OF A PREFERENCE FOR SWEETS, AND WE TEND TO HAVE FEWER DOPAMINE D2 RECEPTORS IN A KEY BRAIN STRUCTURE CALLED THE STRIATUM.

(act) :21 o/c with obesity

We are using as a model sweetness because it’s the ancient food

reward. Almost every other study in animals that looks for rewards

uses something sweet. And we are showing that this kind of biological

thing that happens — that as you age, you lose, you know, your

interest for sweetness — that is also already impaired. We don’t

see it in the group with obesity.

IN OTHER WORDS, OBESITY MAY BE CHANGING THE WAY THE BRAIN RESPONDS TO THINGS THAT WE EAT. PEPINO’S TEAM STUDIED PEOPLE WITH AND WITHOUT OBESITY, MEASURING THEIR PREFERENCE FOR SWEETNESS AND THEN CONDUTING PET SCANS ON THEIR BRAINS TO LOOK FOR D2 RECEPTORS. IN PEOPLE WITHOUT OBESITY…

(act) :28 o/c in obesity

The lower the amount of D2 receptor that they had, the more

concentrated sugar that the liked. And we know that this is

similar to what has been shown in animals. If you give them

a blocker of this receptor, the less D2 you have, the more

sugar the animal will go and prefer. Now interestingly, these

observations that we found in people without obesity, we didn’t

find them in people with obesity. So there is a dysregulation,

or there is an association with a dysfunction in obesity.

CO-INVESTIGATOR TAMARA HERSHEY SAYS THAT PET SCANS ON STUDY VOLUNTEERS USED A SPECIAL BINDING MOLECULE THAT VERY ACCURATELY IDENTIFIED DOPAMINE RECEPTORS.

(act) :17 o/c misidentifying it

That just gives us a little more strength in our, specificity,

in our conclusions about the role of D2 receptors in obesity.

We’re still, like, just feeling one “leg of the elephant” here,

but at least we’re sure it’s the leg, and not…we’re not

misidentifying it.

HERSHEY SAYS THE ASSOCIATION BETWEEN THOSE BRAIN RECEPTORS AND AGE WAS ABLE TO PREDICT THE PREFERENCE FOR SWEETNESS IN NORMAL-WEIGHT PEOPLE.

(act) :22 o/c D2 receptors

Some people liking it a lot, some people not liking it a lot.

There’s also a lot of individual difference in D2 receptors —

some people high; some people low. When we look at how those

go together across all of the people, half of the variance,

or the differences, between people were explained by the

differences in D2 receptors.

BUT PEPINO SAYS IT WAS DIFFERENT FOR PEOPLE WITH OBESITY.

(act) :10 o/c no obesity

In the group of people with obesity, we were unable to look

at…find the same relationships between dopamine and sweetness

that were so clear in the people that had no obesity.

THEY REPORT THEIR FINDINGS IN THE JOURNAL DIABETES. I’M JIM DRYDEN…

RUNS 2:58