Staying warm: What does an unheated room do to your body?

He's wearing shorts and an open shirt (see pic), starts off at 21C/70F and the temp drops to 10C/50F. It's no surprise his body and blood flow reacts to maintain core body temp.

(Edit: my own experience mirrors the article experiment.)

I never heat my house in San Francisco, and it frequently gets down to/below 10C/50F in the winter, and below 13C/55F at other times of the year. If I'm not moving around, just standing at my (standing) desk, then yeah I get cold, so I put on extra layers, a knit cap, and/or fingerless knit wool gloves. Often I'll already have wool socks on.

Btw a knit wool cap gets very hot especially if you have a full head of hair. Someone taught me that you can roll up the edges of the cap to dial down the heat. My partner smirks at me when I do this - she says I'm wearing a yamaka - but it works great, and you can fine-tune your temperature very well this way.

Nighttime temps in the Kalihari dessert can drop to around freezing and the San people have been sleeping basically naked in those conditions for thousands of years like it's no big deal.

It's amazing what the body can adapt to when exposed to the right stimulus.

Evidently your lightly-clothed body starts working harder once air temperature reaches 18C/64F. At 10C/50F your brain will work more slowly.