Less Hunger after a Fast (Patreon)

Hey everyone,

So I just released a video on prolonged fasting called What happens if you Don't Eat for 44 Days? and thought I’d share with you guys a couple interesting things that didn’t make it into the video.

Regarding the apparent reduction of hunger after a long fast, a reduction in insulin might not be the only way you end up getting full more easily. As explained in the video, leptin is a hormone that makes you feel full. When you secrete too much insulin (like in the case of obesity), your leptin signal to the brain is blocked.

So the other thing is that when you stop eating, your hunger hormone leptin goes down. This might seem counter intuitive because more leptin makes you feel full. But, in obesity people are overeating so often that their leptin is always high and this is thought to lead to “leptin resistance.” It’s like a bad smelling room: if you stay in the room long enough you can’t smell it anymore. With leptin resistance, your brain can’t smell the leptin and it’s harder to get the “I’m full” signal. So, the idea is that when you’re fasting, because leptin finally goes down… it’s like your brain stepped out of the smelly room for a while. Then when you finally eat again and leptin goes up(R), your brain can actually smell the leptin - and you get a proper satiety signal and you feel full.(R)

In fact, I initially had leptin included in the starting animation, but ended up taking it out because I thought it would complicate/be too much jargon to explain this leptin lowering effect and the insulin thing (which I suspect is the more robust mechanism).

By the way, all these solid lines are recreations of graphs from different studies. At 00:52, you’ll see on the bottom right hand corner of the screen the studies that each line is based on. (The dotted line for BDNF is to indicate that I’m not sure the exact trajectory of BDNF, but the study referenced simply says that BDNF increased 3.5x from baseline at 48 hours.) The study that the leptin line is based on is Leptin levels decline steady during prolonged fasting in lean children. (Another reason I didn’t end up including the leptin graph: I couldn’t find a study looking at leptin levels in adults during prolonged fasting.)

If you need a convenient reminder on how to fast, you can grab this shirt here.

Also, what did you guys think of the thumbnail and my appearance on the video?  I’m really happy how the video came out, but it’s performing a bit worse than I expected. I was wondering if (a) it was so uncharacteristic of the channel that my subscribers (you guys) scrolled past it thinking it wasn’t a WIL video, or (b) because the thumbnail is more on the youtube-y CLICKMEPLEASE side that the people who clicked on the video didn’t stick around very long because they were expecting more of a “I fasted for 44 days and this is what happened to me!!” rather than a scientific breakdown of what happens during very prolonged fasts.

Keen to hear any comments or questions on the video!

-Joseph