An estimate of metabolic age from a body-composition device fell by 0.94 years during a six-month Mediterranean diet follow-up. Participants also lost 2.60 kilograms, while body mass index (BMI) fell by 1.02 kg/m². The changes were statistically significant. But the result does not show that the diet slowed biological aging. The researchers analyzed routinely collected records without a concurrent control group or random assignment, so the study cannot establish a cause.
That distinction matters because the device did not directly measure biological or epigenetic aging. Body composition was measured with a Tanita MC-580 segmental BIA device, while metabolic age was a proprietary composite derived from basal metabolic rate and body-composition-related parameters. In other words, it is a device-generated surrogate, or stand-in estimate, rather than a direct measure of biological aging.
The signal in the expanded analysis
The researchers asked whether body-composition changes were associated with changes in the device estimate after adjustment for weight change. In the expanded regression model, changes in muscle-to-fat ratio, visceral fat and protein mass were each significantly associated with metabolic-age change. All three associations had p-values below 0.001. The change in weight-adjusted waist index, or WWI, was not statistically significant, with p=0.124.
Adding the body-composition measures raised the share of variation explained by the model from 20.4% to 45.7%, a statistically significant increase. The base model included weight change, age, sex and baseline metabolic age; weight change and baseline metabolic age showed significant associations with the outcome. The authors interpret the larger model as showing adjusted associations in a composite device estimate, not evidence that any one body-composition measure independently determines metabolic or biological aging.
What the records can and cannot show
The comparison was within person. Each participant's six-month reading was set against that person's baseline value, and metabolic-age change was defined as the six-month value minus baseline. The additional variables entered after a base model that included weight change, age, sex and baseline metabolic age.
The diet exposure was dietitian-guided Mediterranean diet counseling. Adherence, however, was assessed from clinical records without a validated adherence scale, dietary recall, food diary, food-frequency questionnaire or objective nutritional biomarker. That means the analysis cannot establish that counseling caused the observed change.
This was a retrospective observational analysis of routinely collected records, and available records were screened sequentially without prospective randomization or investigator allocation. With no control group, changes over time cannot be attributed definitively to the Mediterranean diet. The authors describe their regression results as adjusted associations or correlates of change in the device-derived estimate, not evidence that the variables independently determine metabolic or biological aging.
Who was included
Of 465 baseline records screened, 51 were excluded. The final complete-case cohort included 414 participants, or 89.0% of those screened. The mean age was 40.78 years, with a range of 19 to 70. Women made up 342 participants (82.6%), and men 72 (17.4%).
The report states that the study received institutional ethics approval and followed the Declaration of Helsinki and national ethical standards. No funding was reported, and the authors declared no conflicts of interest.
The number has a narrow meaning
For readers who track a metabolic-age number, the central caution is simple. A lower reading in this study was a change in a proprietary device surrogate observed alongside changes in body composition, not a direct measurement of biological or epigenetic aging. The analysis supports an association within this dataset, but it does not establish that the Mediterranean diet caused the change or that the body-composition variables independently determine aging.
Paper data and sources
Original title: Weight loss–independent associations of body composition changes with device-derived metabolic age during Mediterranean diet follow-up
Authors: Hatır A, Onmaz M, Acar R
Journal/Repository: Revista da Associacao Medica Brasileira (1992)
Status: Peer-reviewed
First online: 2026-10-09
DOI: Not available
Original paper · Full text