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How much are we shaped by our beliefs? What if what we believe is not true?

We know that our beliefs shape our thinking and action. But can it affect even our body's natural functions? 


Take a look at the 2 brands of milkshakes above.

First we have "Indulgence" - a decadent milkshake, 620 calories, 30g of fat, 56g of sugar - it makes ice-cream look like salad.

Then we have "Sensi-shake" - 0% fat, 20g of sugar (but all from ilk and yoghurt, and just 140 calories - guilt-free satisfaction.

Surely, we can guess the effects of the both milkshakes. For example, which do you think will make people more satiated? Indulgence or Sensi-shake?

Crum et al aimed to find out.


  • 46 participants were invited to try out milkshakes

  • They were hooked up to an IV during the test 

  • They were then given either of the milkshakes. 

  • They were asked to first read the label of the respective milkshakes. After reading, they were then asked to finish drinking the milkshake.

  • Throughout this time, the IV was monitoring their blood samples. Specifically they were trying to monitor a neuropeptide called Ghrelin, or more commonly referred to as the "hunger hormone".

  • As the hunger hormone, Ghrelin is secreted when we have not eaten for a while, to signal to our brains  - hey it's time to consume food. Once secreted, Ghrelin also slows down our metabolism - we break down and store food much less quickly in case we don't find new sources. After we've eaten something, this process is reversed- ghrelin levels fall, signalling to our brains - ok you can stop eating now, and revvin up metabolism.

  • The participants went through 2 rounds of the above, so that they could try both milkshakes.


Image from  Dr. Alia Crum | TEDxTraverseCity

The results?


Well as expected. 


The calorically dense "Indulgent" milkshake, with the generous amount of sugar and fat caused Ghrelin levels to drop significantly after consumption. In contrast, the far lighter "Sensi-shake" only triggered a small drop in Ghrelin levels.


"Indulgent" made the participants full, while "sensi-shake" did not completely satisfy them. It's pretty simple really. 


But there's just one catch. 

sensi vs indulgence.png

Image from  Dr. Alia Crum | TEDxTraverseCity

While they were packaged in different labels, both shakes were exactly the same.

All participants drank the same exact milkshake - the "actual" milkshake in the middle column above. 

This greatly undermines our previous conclusion. Not only were participants mentally tricked into believing that they consuming something "Sensi-shake" or "Indulgence" when it always the same milkshake, their bodies physically reacted to what they believed instead of what actually happened.


Ghrelin was secreted based on subjective reality and not objective reality. And it worked both ways. Whether we thought we were satisfied or not satisfied, our bodies reacted accordingly.

This brings to question how can this be the case? And this is not an isolated example. Exercie only works if you believed you have exercised. Pain medication works better if you see it being adminisered. There are even surgeries conducted which are as effective as actual surgery (in fact more effective, becuase there is less risk). How does any of this make sense? 

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