The need to find fuel to generate energy is a profound drive within the biology of all living organisms: we all need food to survive. So it’s not surprising that our bodies have such a complex system to control food intake, driven by hormones.
The “nocebo effect” is like the placebo effect, except in reverse. Whereas placebos trick people into feeling better, “nocebos” are things that make people feel worse, even though they don’t really exist. They can even kill people! Here’s how we can trick ourselves into dying, and how doctors may have found a cure.
We’ve seen this in numerous aspects – WiFi sickness (not real), those who claim issues relating to gluten (as opposed to those who actually are sensitive/allergic)… A lot of chemical intolerance tests do show this as well.