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.
Charney and colleagues realised that the survival school was a perfect controlled environment for the study of acute stress on the human body. They got permission to expose regular and special forces soldiers to tests before and after the training, and before and immediately after mock interrogations. These tests revealed that blood levels of a brain chemical called neuropeptide Y (NPY) correlated strongly with the soldiers’ ability to cope. Those with more NPY performed better during the interrogations. What’s more, the special forces soldiers, known for being especially cool under stress, had significantly higher levels of NPY compared with regular troops, both before and after the training. Twenty-four hours after the programme had finished, NPY levels in the special forces soldiers were back to their baseline, while those in regular soldiers were still considerably lower.