Mitochondria, stress and the energy to function

From calories to function

EPK asks whether an eating pattern supplies enough energy for daily function and can be sustained without persistent hunger, exhaustion and preoccupation with food. Martin Picard’s mitochondrial research adds a related question: how does the body transform and allocate the energy it receives? These are connected questions, but they require different measurements.

Food intake, resting energy expenditure and cellular energy transformation are not interchangeable. Mitochondrial research can inform EPK without demonstrating that an intake target or readiness category is valid.

Mitochondria and the stress response

In a 2015 mouse experiment, Picard and colleagues found that mitochondrial perturbations altered neuroendocrine, metabolic, inflammatory and transcriptional responses to acute stress. This supports a role for mitochondria in shaping the stress response. It does not demonstrate that ordinary calorie restriction causes the same changes in people. [1]

In a human observational study, a mitochondrial health index measured in blood cells was associated with caregiving stress and mood. This connects biological measurements with lived experience, but it does not establish which caused which or measure mitochondrial function in the brain. It was not a feeding trial. [2]

Higher expenditure does not always mean better health

Sturm and colleagues combined experimental cell work with evidence from patients with mitochondrial disease. Impaired oxidative phosphorylation could coexist with increased energy expenditure. For EPK, this means a high resting metabolic rate cannot automatically be interpreted as plentiful useful energy or superior function. [3]

In another experiment, chronic glucocorticoid exposure increased energy expenditure in three human fibroblast lines and was associated with cellular ageing measures. Cultured cells are not whole people: these findings do not show that routine dieting shortens human lifespan. They do show why more energy expenditure and better biological function must be distinguished. [4]

The preliminary chamber study

Quanta’s July 2026 feature describes a small metabolic-chamber study whose results were under review at publication. Participants with rare mitochondrial disease reportedly had higher resting costs but less additional expenditure during ordinary life. This suggests a possible trade-off between maintaining basic processes and activity; it remains preliminary evidence rather than a general calorie prescription. [5]

The same feature discusses Picard’s hypothesis about mitochondria and consciousness. That broader proposal is not demonstrated by the stress studies and is not needed to investigate the narrower relationship between energy metabolism, fatigue and behaviour. [5]

What this contributes to EPK

The useful distinction is between insufficient fuel, the cost of maintaining basic processes, and impaired cellular utilisation. A person’s reported fatigue cannot identify which explanation applies. Nor can increasing food intake be assumed to repair a mitochondrial disorder.

EPK research could test whether improving insufficient intake improves sleep, daily function and dietary burden, while measuring intake, expenditure and body composition separately. Where feasible, cellular measurements would test a proposed mechanism rather than merely illustrate it. Improvements in function would matter even when body-mass changes are modest.

These findings are most useful to the papers on metabolic flexibility, functional capacity, cognition and immune regulation, with links to the behavioural framework. They support investigating energy and function together; they do not establish a universal 25 kcal/kg/day minimum or show that every calorie deficit is harmful.

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.