Healthspan needs outcomes beyond metabolic rate

Define the benefit

Healthspan concerns years lived with health and useful function. A short trial can measure mobility, symptoms or disease-risk markers, but cannot by itself show a longer life. Changes in RMR are physiological observations whose value depends on accompanying outcomes.

An intervention with a functional endpoint

The LIFE trial randomized 1,635 older adults at risk of disability. Structured activity reduced major mobility disability over about 2.6 years, from 35.5% in the comparison group to 30.1% [1]. This provides an example of a meaningful endpoint and a plausible activity comparator for Paper 4.

Lower intake does not always mean worse health

In CALERIE, the restriction group achieved approximately 11.7% calorie restriction over two years, maintained weight loss and improved cardiometabolic risk markers. Body-weight-adjusted RMR differed from controls at 12 months but not at 24 months [2]. These findings challenge any blanket claim that lower intake or expenditure necessarily signals harm. They do not demonstrate longer human lifespan.

Several CALERIE publications concern overlapping participants. Multiple reports can illuminate different outcomes without representing independent replications.

Use outcomes to judge the hypothesis

For Papers 1 and 5, the question is whether EPK identifies people whose intake is insufficient for their circumstances and function. For Papers 4 and 6, repeated performance measures may help define resilience. Prespecify a primary outcome and test whether the proposed measure adds practical value beyond intake, composition and activity. A rise or fall in RMR should not predetermine the interpretation.

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.