The psychology of metabolism:
For a long time scientists thought ghrelin levels fluctuated in response to nutrients that the ghrelin met in the stomach. So put in a big meal, ghrelin responds one way; put in a small snack and it responds another way.
But that’s not what Crum found in her milkshake study.
If you believed you were drinking the indulgent shake, she says, your body responded as if you had consumed much more.
“The ghrelin levels dropped about three times more when people were consuming the indulgent shake (or thought they were consuming the indulgent shake),” she says, compared to the people who drank the sensible shake (or thought that’s what they were drinking).