Sapolsky, stress and energy: what belongs in EPK research?

Acute adaptation and prolonged stress

Why Zebras Don't Get Ulcers provides a framework for understanding how a useful short-term stress response can become costly when repeatedly activated. Sapolsky, Romero and Munck's endocrine review adds an important qualification: glucocorticoids can permit, stimulate, suppress or prepare responses, depending on timing and context. Cortisol is not simply a toxin or a direct measure of energy deficiency. [1,2]

Food shortage and food insecurity are different exposures

A measured calorie deficit concerns energy balance. Food insecurity concerns uncertain or inadequate access to food; social threat and perceived lack of control are further exposures. They can overlap, but one cannot be substituted for another. Sapolsky's review of primate hierarchies shows that the relation between rank and stress-related physiology depends on social organisation and circumstances. It is contextual evidence, not a controlled human feeding experiment. [3]

A more direct human link comes from Tomiyama and colleagues, not Sapolsky: a three-week factorial experiment assigned 121 women to restriction, monitoring, both or neither. Restriction to 1,200 kcal/day increased cortisol output; monitoring increased perceived stress. The experiment does not establish that cortisol prevents weight loss or that every deficit has this effect. [4]

Behaviour and cognition

Behave encourages explanations that account for biology and environment rather than interpreting behaviour in isolation. For EPK, this supports investigating hunger, sleep, social circumstances and adherence together; it does not validate a particular energy target. This is an application of the framework, not a conclusion tested in the book. [5]

Sapolsky's work on glucocorticoids and the nervous system is relevant to hypotheses about stress and cognitive function. His review distinguishes dendritic changes, neuronal injury and vulnerability to other insults. Much of this evidence is experimental and preclinical. It cannot establish that everyday dieting damages the human hippocampus or causes cognitive ageing. [6]

How to use this evidence

EPK studies should record energy intake and expenditure, sleep, perceived stress, food security and social support separately. If cortisol is measured, sampling time and repeated measurements matter. The strongest contribution is a study design that can separate energetic from psychosocial explanations. Immune and cognitive claims require their own outcomes; supportive biological context is not proof of EPK or Proportional Danger Theory.

Related working papers

Read the relevant PDFs: EPK–001 to 007 are the revised version 1.2 papers; EPK–008 to 010 are version 1.0 supplements. Earlier PDFs and DOI records remain on the paper archive.