A Label Is More Than A Label. The physiology of belief.
The Milkshake Study found that nutritional labels are not just labels; they evoke a set of beliefs that actually affect the body's physiological processing of the nutrients that are consumed.
Basically, it is like the placebo (or nocebo) effect works.
In this experiment, a batch of vanilla milkshakes was created, then divided into two batches that were labelled in 2 different ways. One batch was called Sensishake — advertised as 0% fat, 0 added sugar, and only 140 calories. The other batch, called Indulgence, according to the label, it was high in sugar and fat to account for 620 calories. In truth, the shakes had 300 calories each. Both before and after the people in the study drank their shakes, nurses measured their levels of a hormone called ghrelin.
Ghrelin, secreted in the gut, is called the hunger hormone. When ghrelin levels in the stomach rise, that signals the brain that you are hungry. It also slows metabolism just in case you might not find that food. And if you have a big meal then your ghrelin levels drop. That signals the mind that you've had enough, and the metabolism speeds up to burn the calories we've just ingested. On the other hand, if you only have a small salad, your ghrelin levels don't drop that much, and metabolism doesn't get triggered in the same way. For a long time, scientists thought ghrelin fluctuated in response to nutrients that it met in the stomach.
But that's not what has been found in the milkshake study.
In the study, the ghrelin levels dropped about 3 times more when people thought they were consuming the indulgent shake compared to the people who thought that they were drinking the sensible shake. Participants' satiety was consistent with what they believed they were consuming rather than the actual nutritional value of what they consumed.
Does that mean the facts don't matter, that it's our beliefs of the facts that matter?
NO. BUT the classic metabolic model needs some rethinking.
Our beliefs matter in virtually every domain, in everything we do. How much is a mystery, but so far we have not given enough credit to the role of our beliefs in determining our physiology, our reality.
SOURCE: https://pubmed.ncbi.nlm.nih.gov/21574706/