But as I said before, the best placebo studies involve a little trickery, and thank God a few scientists are willing to go there. The landmark study comes from Alia Crum at Stanford. As a grad student, Crum did an experiment where she found that just telling hotel workers how much exercise they were getting at work could have positive effects on their health. So in 2010, she took the next logical step. She passed out two types of milkshake—a 620-calorie version and a 140-calorie one, complete with labels that claimed they were either indulgent or diet—to two separate groups. As one might expect, the people’s gut chemistry behaved very differently depending on which shake they got, with their hunger hormones (which are also involved in metabolism) dropping much more with the fatty shake.
Except the thing is that she lied—both the shakes were 380 calories. In other words, their bellies responded not to what they were eating but to what they thought they were eating. The following year, a team at Purdue told patients they had invented special solid foods that turned to liquid once in the stomach as well as liquid foods that turn to solid. Some people got actual solids and liquids while others received the magical stomach-changing kinds. Of course, they were actually the exact same meals, and all had the same number of calories.
Naturally, people could feel the nonexisting transformations. The nontransforming-liquid drinkers were all quickly hungry, while the people drinking the “liquid-to-solid” said things like, “I could barely swallow the liquid it was so thick,” “I am so full I can barely finish the glass,” and my favorite, “It came out like a solid, too.”
Meanwhile the people eating the real solid could barely finish them all while those eating the “solid-to-liquid” said, “It hardly feels like I ate anything,” “It feels like I drank a bunch of liquid,” and “It immediately went away when the cubes turned to liquid in my stomach.”
Giggle all you want, but can you really be sure that given the same situation you wouldn’t feel exactly the same thing? The subjects in an experiment like this aren’t chosen because they are morons; they’re chosen because they are us.
But here’s the stranger bit: Their bodies’ physical chemistry responded accordingly, too. The people who thought they were eating liquids passed them through their systems like liquids. Their hunger hormones, insulin, and other metabolic hormones fell in line with what they expected, not what they ate.