April 14, 2014
“Labels are not just labels; they evoke a set of beliefs,” says Alia Crum, a clinical psychologist who does research at the Columbia Business School in New York.
A couple of years ago, Crum found herself considering what seems like a pretty strange question.
She wanted to know whether the information conveyed by a nutritional label could physically change what happens to you — “whether these labels get under the skin literally,” she says, “and actually affect the body’s physiological processing of the nutrients that are consumed.”
Both before and after the people in the study drank their shakes, nurses measured their levels of a hormone called ghrelin.
Ghrelin is a hormone secreted in the gut … the hunger hormone. When ghrelin levels in the stomach rise, that signals the brain that it’s time to seek out food.
“It also slows metabolism,” Crum says, “just in case you might not find that food.”
But after your ghrelin rises, and you have a big meal (say a cheeseburger and a side of fries), then your ghrelin levels drop. That signals the mind, Crum says, that “you’ve had enough here, and I’m going to start revving up the metabolism so we can 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 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.
Dr. Alia Crum