Today's episode of Rationally Speaking is sponsored by Givewell, a nonprofit dedicated to finding outstanding charities and publishing their full analysis to help donors decide where to give.

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It's free and available to everyone online. Check them out at give well.org. Welcome to Rationally Speaking, the podcast where we explore the borderlands between reason and nonsense.

I'm your host, Julia Galef, and I'm here with today's guest, Stefan Giena.

Stefan is a researcher and a science consultant.

His background is in neuroscience.

And well, his PhD is in neurobiology.

And his focus is obesity research.

So his recently published book is called The Hungry Brain.

And we're going to be talking today about the

science of why people gain weight, why we see obesity rising in the U.S. and elsewhere.

So, Stefan, welcome to the show. Thanks. Great to be here. I'll admit, before we start talking,

that I've been kind of avoiding this topic as a podcast episode for, oh God, a year or two at least.

Which is not because I don't think it's interesting or important.

It's just so complicated and also contentious and that those two things together are like a recipe for listeners getting mad at you because you, you know, didn't bring up a certain study that was really important or you like didn't challenge a certain factual claim and I'm sure that's going to happen. But I basically just, I don't want to avoid all topics in this category forever because of that.

So maybe I should just be clear for you and especially for listeners what my goal is with this episode.

I'm not going to be able to cover all of the empirical evidence.

Stefan isn't going to be able to either, even though he knows far more of it than I do.

But what I'm hoping we can really do is get really clear on what Stefan's leading model is

of why people gain weight and where it diverges from other leading hypotheses of weight gain, and then start to talk about

what evidence would help disambiguate between those theories without necessarily being able to

...