Joanne Lee SmithChronic pain and symptoms recovery Nurse / Coach

The Power of Expectations on Your Body

11 Aug 2026 · 1 min

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In this segment of her YouTube video, Joanne Smith explains a well‑known experiment often cited in books about expectation effects. Participants were given milkshakes that were described either as a high‑calorie, filling drink or as a low‑fat, slimline drink. Although both drinks were identical—300 calories each—their bodies reacted differently. Those told the milkshake was high‑calorie showed higher levels of ghrelin, the hunger hormone, while those told it was low‑fat showed lower ghrelin. Smith uses this example to illustrate how the brain’s expectations can directly shape physiological responses, even when the actual nutritional content is the same.

Chapters

One of the famous examples that's used in the book, which you might have heard about, is the milkshake research exercise, where they gave a group of people a really filling, really high-calorie milkshake, and they measured their levels of ghrelin. I always get that hormone wrong, but it's the hunger hormone. And they gave another group a really low fat slimline version, and they measured their hunger hormone, and the results are incredible because the body responded based upon what it expected, what it believed, what it was told about these milkshakes. But the real truth behind it is that the milkshakes were both exactly the same. They were both 300 calories. All the people were given the exact same nutrition, the same amount, but their body responded based upon what they were expecting