Julia Beluz, Health Reporter of Vox.

Sean, podcast master of Vox.

I want to take you somewhere today.

I'm in. I spend too much time in the studio.

Well, it's kind of a studio too.

It's like an 11 by 11 foot space.

But fewer than 100 people every year enter these rooms

at the National Institutes of Health.

And this year I was one of them.

Wow.

And it's used to unlock one of the greatest mysteries

of the human body.

Which one?

The metabolism.

The metabolism is something we talk about all the time,

but don't really understand, is my guess.

Some of you think your metabolism feels like this, a slow drip,

with ripples of excess fat slowly accumulating

around your waist and everywhere else.

Yeah, there's a big gap between how we talk about it

and how scientists talk about it.

So we talk about it.

...