Short Wave - This Is Your Brain On Dessert

Episode Date: February 21, 2025

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 and 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 [e-mail]! 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.See 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

You're listening to Shortwave from NPR. Hey, Short Waver is 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. I am always happy to be here, but I'll be honest, I'm only here because I heard we might have dessert. Okay. 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 fog. That's all well and good, but again, I'm going to stress that I was promised dessert.

Oh, fine. I guess we lie. All of that on this episode of Shortwave, the science podcast from NPR. All right, we're back, and we're going to start with dessert because I'm that kind of person. What is your favorite kind of dessert? Key lime pie. Pussy!

Wait, what? I don't like it. All right, we're not going to do. debate that right here right now. All desserts are considered, but I pose this exact same question to scientist Henning Fenzelalau. He said gummy bears. Correct. Which makes sense. Which makes sense, you too, because Henning is from Bonn, Germany, the town where Haribo gummy candies began. Yeah. This is from my hometown. So I'm still a big fan of it. Maybe driven by my childhood. I don't know. 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. 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? Scott, it's our brains. So one of the ways our body signals that were 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. 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. Yes. So when the researchers blocked this pathway, the mice seemed less interested in sugar. Interesting. 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. 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, my other question, are there any hypotheses here for why our brains are set up this way?

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?

Okay. Let's talk seals next. I hear some of them are doing science now. Yeah, they're trying to take my job. It's okay because we're all going to the sugar-eating jobs. Yeah. Researchers figured out a way to measure the health of parts of the ocean by tracking and weighing elephant seals. 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? 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. How do you weigh a seal? According to lead researcher Roxanne Beltron, a huge police 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 her pups. Then using binoculars and cameras, the scientists identify previously tagged seals they want to weigh, and then they weigh them. 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. 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. Hear me out. What if instead of weighing seals, they just did like a fish census? 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.

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. 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. Desert check. Mm-hmm. Seals check. Next, collecting water from fog, which does not strike me as a new thing, right? 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. So this study, it's very cool. It focuses on Alto Ospiccio, 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. How does this actually work? Like, is this similar to like collecting condensation? 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. How much of an impact could this make on a city's water supply? Well, after collecting data at various 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. 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 Espicio 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. You know what we just did there? What? We went from dessert to desert. Waka, waka.

He spells. He hosts. He's Scott Dutro. You can hear more of Scott on Consider This and P.R.'s afternoon podcast about what the news means for you. This episode was produced by Hannah Chin, Burley McCoy, and Alejandro Marquez Hansi. It was edited by Rebecca Ramirez and Christopher and Talianta. Tyler Jones checked the facts.

Becky Brown and Jimmy Keely for the audio engineers. I'm Emily Kwong. And I'm Regina Barber. Thank you for listening to Shorewave, the science podcast from NPR. Scott, thanks so much. You ever thought about hosting a science podcast? I would love to. You have the brain.

Is it just the glasses? It's the glasses.