Stanford researcher explains how beliefs alter physical reality

PsyPost’s PodWatch highlights interesting clips from recent podcasts related to psychology and neuroscience.

On Thursday, November 20, The Psychology Podcast, hosted by Dr. Scott Barry Kaufman, featuring Dr. Alia Crum, explored the science behind the mind-body connection. Dr. Crum is a principal investigator at the Stanford Mind & Body Lab who studies how subjective mindsets can alter objective physiological realities. The episode focused on her groundbreaking experiments regarding the placebo effect, exercise, and the biological impact of our beliefs about food.

At roughly the 8-minute mark, Dr. Crum describes an experiment she conducted with hotel housekeepers to test the placebo effect outside of a clinical setting. She discovered that while these women were physically active during their shifts, they did not believe they exercised enough to be healthy. Once researchers informed the workers that their job met the Surgeon General’s fitness guidelines, the women experienced measurable drops in weight and blood pressure despite not changing their daily behaviors.

The conversation shifts to diet and metabolism around the 10-minute mark, specifically focusing on the hormone ghrelin. This biological chemical signals hunger to the brain and slows down metabolism when the body thinks it needs food. Dr. Crum explained that typically, ghrelin levels drop after a person eats a large meal to signal that the body is full.

To test if the mind could influence this biological process, researchers gave participants identical milkshakes containing roughly 380 calories. One group was told the drink was an indulgent, high-calorie treat, while the other group believed they were drinking a low-calorie, sensible diet shake. The team then measured the ghrelin levels in the participants’ bloodstreams to see how their metabolisms reacted.

The results revealed that those who believed they consumed the high-calorie shake experienced a drop in ghrelin three times greater than the group that believed they drank the diet shake. This indicates that the body’s physical satiety response is driven partly by the mental expectation of how much food was consumed. Dr. Crum noted that thinking a meal is “sensible” or “restricted” might actually keep hunger hormones high and metabolism slow, counteracting the goals of a diet.

You can listen to the full interview here.