Study finds diet changes shift aging markers in four weeks

A month was enough to move blood markers tied to biological age in 104 adults aged 65 to 75, but the clearest shift did not come from the higher-fat, lower-carb arm that keto readers will notice first. The strongest signal landed in the lower-fat, higher-carbohydrate omnivorous group, a result that reads more like a biomarker reality check than a reset button for aging.

The trial, led by Dr Caitlin Andrews of the University of Sydney’s School of Life and Environmental Sciences and the Charles Perkins Centre, used a 2 by 2 factorial design as part of the Nutrition for Healthy Living study. Participants were randomly assigned for four weeks to one of four diets: omnivorous high-fat, omnivorous high-carbohydrate, semi-vegetarian high-fat, or semi-vegetarian high-carbohydrate. All four plans delivered 14 percent of energy from protein, while the mix shifted along two axes, animal versus plant protein and high-fat versus high-carbohydrate intake.

Researchers tracked 20 blood-based biomarkers linked to biological age, including cholesterol, insulin and C-reactive protein, and turned them into a KDM-derived deltaAge measure based on the Klemera-Doubal Method. The omnivorous high-fat group, the one that most closely resembled participants’ usual diets, showed no meaningful change in deltaAge. Compared with that group, the omnivorous high-carbohydrate arm showed a significant reduction. The semi-vegetarian high-fat and semi-vegetarian high-carbohydrate groups also showed reductions relative to the omnivorous high-fat group, although not all of those changes reached statistical significance.

For people following keto or another low-carb plan, the practical takeaway is not that low-carb lost, but that the label matters less than the whole pattern. This study included a higher-fat, lower-carbohydrate arm, so it sits close to the low-carb conversation, yet the result suggests that broader diet composition, including where protein comes from and how much carbohydrate is traded for fat, may drive short-term biomarker changes more than a simple keto versus non-keto split. That is useful, but it is not proof that any of these patterns slowed aging in a lasting way.

Andrews and her co-authors cautioned that the shifts may reflect acute physiological responsiveness rather than a true change in aging trajectory, and said longer-term treatment would be needed to see whether disease risk actually falls. That caution fits the wider market for biological-age testing, which can cost from about US$30 to more than $1,000 and is not approved for medical decision-making. The markers moved in four weeks, but the harder question is whether those changes stay moved long enough to matter.