This Is Your Brain On Dessert

Ever eat a full meal ... and find you still have room for dessert? If so, you're not alone. Sugar is a quick form of energy that many people crave — even when they're full. Today, hosts Emily Kwong https://www.npr.org/people/767284140/emily-kwong and Regina G. Barber https://www.npr.org/people/1082526815/regina-g-barber dive into a new study on the neural origins of the "dessert brain." Want us to cover more neuroscience on the show? Let your voice be counted by emailing [email protected] mailto:[email protected]! Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave http://plus.npr.org/shortwave. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:01Speaker 00

  We will learn something on election night, but not everything. There's a lot we will not know, especially when it comes to close races. And we'll know much more the next morning and the morning after that. So save yourself a little time scrolling and listen to Up First. We'll be there when you wake up each and every morning this week with the latest midterm election news.

• 0:24Emily Kwong?

  You're listening to Short Wave from NPR.

• 0:30Regina Barber?

  Hey, Short Wavers. Regina Barber here. And Emily Kwong. With our biweekly science news roundup, featuring the hosts of All Things Considered. And today we have fellow nerd Scott Detrow.

• 0:39Speaker 03

  I am always happy to be here, but I'll be honest, I'm only here because I heard we might have dessert.

• 0:44Regina Barber?

  Oh, OK. We should have brought some in. There might be some in the building we can look after. But we're here to talk to you about why our dessert craving actually begins in our brain. How elephant seals are helping scientists monitor ocean health. And then finding water in the desert. Fuck.

• 1:01Speaker 03

  That's all well and good, but again, I'm going to stress that I was promised dessert.

• 1:05Regina Barber?

  Oh, fun. Well, I guess we lie.

• 1:06Speaker 03

  OK.

• 1:07Regina Barber?

  All of that on this episode of Short Wave, the science podcast from NPR.

• 1:14Speaker 04

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• 1:18Speaker 05

  Oh, Kevin, it feels good to be back. It sure does, Casey. And what a time. The world is talking about AI and what's going on in Silicon Valley. And we are here with a new show to tell you all about it. That's right, Kevin. On our new show, Machine Gods, twice a week, we'll be bringing you the biggest news in tech and bring you unmatched access to the real titans of this industry. You can find Machine Gods from NPR on the NPR app or wherever you get your podcasts.

• 1:42Speaker 03

  Election season feels messier than ever. Attack ads, misinformation, AI. NPR is your antidote. Our network of real, live, human journalists keeps you focused on what's real. With NPR Plus, you directly support journalists on the ground asking questions. And as a thank you, you get dozens of podcasts sponsor-free. Sign up for NPR Plus today at plus.npr.org. All right, we're back. And we're going to start with dessert because I'm that kind of person.

• 2:10Regina Barber?

  What is your favorite kind of dessert?

• 2:12Speaker 03

  Key lime pie.

• 2:13Emily Kwong?

  Classy. Wait, what? I don't like it. All right, we're not going to debate that right here, right now. All desserts are considered, but I posed this exact same question to scientist Henning Fenzelau. He said gummy bears.

• 2:26Speaker 03

  Okay.

• 2:27Emily Kwong?

  Correct. Which makes... I'm fine with both. Which makes sense, you two, because Henning is from Bonn, Germany, the town where Haribo gummy candies began.

• 2:36Speaker 03

  Yeah.

• 2:37Speaker 06

  This is from my hometown, so I'm still a big fan of it, maybe driven by my childhood. I don't know.

• 2:46Emily Kwong?

  They say research is me-search. Okay, so now Henning is a research group leader at the Max Planck Institute for Metabolism Research, and in a new study in the journal Science, his team investigates how our bodies can crave sugar even when our stomachs are full.

• 3:00Speaker 03

  I, along with so many others, have had that happen so many times. Like, why? What is going on? Why are our bodies telling us to do this?

• 3:06Emily Kwong?

  Scott, it's our brains. So one of the ways our body signals that we're full involves these satiety neurons, and they're located in this part of our brain called the hypothalamus. But sugar seems to hijack that system in an interesting way. Yeah, to say the least. So to study how this works, Henning and his colleagues turned to mice, which have similar brains to us, and researchers fed mice to the point of fullness and then gave them sugar. And they noticed that those same neurons signaling satiety were also triggering the release of naturally occurring opiates called beta endorphins, and this flood of opiates in the mouse brain triggered a feeling of reward.

• 3:42Speaker 03

  So let me make sure I'm following that, okay? So their brains are signaling they're full, but they're still, at the same time, tripping more brain wires that are saying, eat more sugar.

• 3:50Emily Kwong?

  Yes, so when the researchers blocked this pathway, the mice seemed less interested in sugar.

• 3:55Speaker 03

  Interesting.

• 3:56Emily Kwong?

  Yeah. And then Henning and his colleagues found the same pathways in humans by looking at donated brain tissue and scanning brains of volunteers who sat in an fMRI machine and were fed a sugar solution through a tube.

• 4:08Speaker 03

  So my first question is, how do I stop being a radio host and do this instead? Take part in these researches? But beyond that-

• 4:14Emily Kwong?

  Impossible to answer.

• 4:16Speaker 03

  My other question, are there any hypotheses here for why our brains are set up this way?

• 4:20Emily Kwong?

  Well, it is consistent with what we know about sugar for survival. Sugar, it signals to our brain, oh, this food is full of energy. It's easy to metabolize. Of course, excess sugar is bad for us. So Henning now wants to know how much this pathway contributes to overeating. Does it lead to the development of obesity? And can this discovery be built into weight loss drugs?

• 4:42Speaker 03

  Okay. Let's talk seals next. I hear some of them are doing science now?

• 4:46Emily Kwong?

  Yeah, they're trying to take my job.

• 4:48Speaker 03

  It's okay, because we're all going to the sugar eating jobs.

• 4:51Emily Kwong?

  Yeah. Researchers figured out a way to measure the health of parts of the ocean by tracking and weighing elephant seals.

• 4:59Speaker 03

  Help me make this connection a little more. Is this, what does seal weight have to do with ocean health? Like, is this, if the seals are eating enough food, we're in good shape?

• 5:07Emily Kwong?

  Something like that, yeah. Because elephant seals, especially the mothers, eat a lot of fish. So how much these moms weigh can tell scientists how many fish there are that year, which has ripple effects for everything that eats those fish and everything that gets eaten by the fish.

• 5:20Speaker 03

  How do you weigh a seal?

• 5:21Emily Kwong?

  According to lead researcher Roxanne Beltran, a huge pulley system, basically. They wait for pregnant females to return from their months-long foraging trip to beaches on the California coast where they give birth and bond with their pups. Then, using binoculars and cameras, the scientists identify previously tagged seals they want to weigh, and then they weigh them.

• 5:39Speaker 07

  It sounds so simple, but weighing a 500-kilogram elephant seal is a lot of work. You have to sedate the seal and then take five people to roll the seal into a sling to be suspended in midair from a tripod, hanging from a scale, so we can read that mass.

• 5:54Emily Kwong?

  So rude. Can you imagine coming back from dinner, dessert perhaps, and then someone's like, hop on the scale? Every day. But anyway, using this method, scientists have weighed seals 600 times in the last two decades.

• 6:09Speaker 03

  Hear me out. What if, instead of weighing seals, they just did like a fish census?

• 6:14Regina Barber?

  Yeah, they can't. So this is part of the ocean that scientists have like a really hard time getting information from. It's called the Twilight Zone, one of my favorite shows. It's hundreds to thousands of feet below the surface. And Roxanne says not knowing the true number of fish in these dark depths is a problem.

• 6:31Speaker 07

  Our counts of fishes range by about 10 orders of magnitude. And we don't know how those numbers fluctuate year after year. And that's what the seals were able to tell us.

• 6:41Regina Barber?

  Roxanne's team published all of these details in the journal Science. So in addition to being a barometer for fish populations, seal health can also teach us about the health of the ocean in general, which is important for climate regulation, food security, and local economies.

• 6:56Speaker 03

  Dessert, check.

• 6:57Regina Barber?

  Mm-hmm.

• 6:58Speaker 03

  Seals, check.

• 6:59Regina Barber?

  Yes.

• 6:59Speaker 03

  Next, collecting water from fog, which does not strike me as a new thing, right?

• 7:04Regina Barber?

  No, it's not new. So fog collection is like an old technique. And scientists have been studying it for at least 40 years. But all of that data came from small villages. And now a new study in the journal Frontiers in Environmental Science shows that fog could be a viable source of drinking water in a big city, too.

• 7:20Emily Kwong?

  So this study, it's very cool. It focuses on Alto Ospito, a city of over 140,000 people in the Atacama Desert in Chile. This is one of the driest deserts in the world, so it's a prime spot to test out fog collection.

• 7:33Speaker 03

  How does this actually work? Like, is this similar to like collecting condensation?

• 7:37Emily Kwong?

  A little bit. Fog is created when large masses of warm air travel from the ocean over the land. And when that warm, wet air hits cold air in the desert, boom, you got fog. Then people can use meshes, nets, or even leaves to condense the fog, collect it in jugs or buckets, which are now full of fresh water.

• 7:55Speaker 03

  How much of an impact could this make on a city's water supply?

• 7:57Regina Barber?

  Well, after collecting data at various like fog collection sites for a year, the researchers used a computer model to map how much water could be collected from fog over this whole region. And they found that fog could supply hundreds of thousands of liters of drinking water per week. Enough to supplement the water demands of under-resourced parts of the city.

• 8:16Emily Kwong?

  The lead author of the study, Virginia Carter of Universidad Mayor in Chile, considers desert fog a sustainable water source. She pointed out that Alto Aspicio struggles in terms of infrastructure, budget, and green spaces. So ultimately, Virginia wants to take this data to city officials so they can make fog collection a reality across the city for drinking water, green spaces, and food gardens.

• 8:38Speaker 03

  You know what we just did there?

• 8:40Emily Kwong?

  What?

• 8:40Speaker 03

  We went from desert to desert. Wakawaka.

• 8:43Emily Kwong?

  He spells. He hosts. He's Scott Detrow.

• 8:48Regina Barber?

  You can hear more of Scott on Consider This, NPR's afternoon podcast about what the news means for you. This episode was produced by Hannah Chen, Berlin McCoy, and Alejandro Marquez Honsay. It was edited by Rebecca Ramirez and Christopher Intagliata.

• 9:01Emily Kwong?

  Tyler Jones checked the facts. Becky Brown and Jimmy Keely were the audio engineers. I'm Emily Kwong.

• 9:06Regina Barber?

  And I'm Regina Barber. Thank you for listening to Short Wave, the science podcast from NPR.

• 9:14Emily Kwong?

  Scott, thanks so much. You ever thought about hosting a science podcast?

• 9:17Speaker 03

  I would love to.

• 9:18Emily Kwong?

  You have the brain.

• 9:19Regina Barber?

  Is it just the glasses?

• 9:20Speaker 03

  It's the glasses.

• 9:24Emily Kwong?

  Stay tuned for the following announcements and messages from our sponsors.