Research perspective · 17 October 2026
Beyond the scales: strength, ageing and measuring function
A grip-strength study raises a useful question for nutrition research: what happens to the person’s capabilities, alongside their body mass?
The outcome should match the ambition
If the aim of eating well is to support a functioning person, a change on the scales cannot be the only outcome we value. For EPK—Energy per Kilogram—the question is whether a sustainable pattern of fuelling supports everyday capability. That ambition needs measurements capable of showing improvement, no change or deterioration.
What the study found
Peterson and colleagues analysed approximately 1,275 middle-aged and older adults in the US Health and Retirement Study. Grip-strength histories spanning 8–10 years were compared with blood DNA-methylation measures. Lower grip strength relative to body mass was associated with less favourable epigenetic ageing measures, although results differed by sex and clock. [1]
Methylation was measured at one time point. The study therefore cannot show that increasing strength slows a person’s epigenetic ageing. Nor did it test an EPK diet. Unmeasured influences and selection into the analysed sample remain possible explanations for part of the association. [1]
A ratio can improve without a stronger hand
Consider a hypothetical person whose grip remains 30 kg while body mass falls from 80 kg to 70 kg. Grip divided by body mass rises from 0.375 to 0.429—around 14%—without an increase in absolute strength. That is arithmetic, not a finding from this cohort.
The same care is needed with kcal/kg/day. At a fixed intake, a falling denominator raises the ratio. A useful EPK analysis should retain intake, body mass and functional measurements separately, rather than allowing a favourable ratio to stand in for an improvement in every component.
How EPK could test function
A prospective study could measure absolute grip and body mass at baseline and follow-up, using a consistent device and protocol. Relative grip could be reported alongside them. Training, illness and changes in medication should be recorded so that an apparent dietary effect is not accepted without considering other explanations.
Daily capability and perceived recovery could be additional outcomes. The primary outcome and comparison should be selected before results are known. If the proposed EPK approach does not improve function, that finding would matter as much as a positive result.
Connections to the working papers
EPK–001 sets out the framework that needs testing; EPK–004 addresses functional capacity; EPK–006 considers ageing and energy. This study is most directly relevant to the choice of functional outcomes. It does not demonstrate a cognitive benefit, a calorie threshold or a required energy surplus. The linked PDFs are existing working papers, not revised releases incorporating this article.
Related research
Research and guidance
Explore more studies in the research library.
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.