The study, published in Aging Cell, found that adults between the ages of 65 and 75 experienced reductions in their estimated ‘biological age’ after following specific diets for just four weeks. Researchers say the findings suggest dietary changes later in life may quickly improve markers linked to aging and overall health.

The research was led by Dr. Caitlin Andrews from the University of Sydney’s School of Life and Environmental Sciences. While the results are promising, the scientists emphasized that the study provides only an early indication rather than definitive proof that diet can reverse aging. They say larger and longer studies are needed to determine whether these biological changes lower disease risk over time and whether the same effects occur in other age groups.

What Is Biological Age?

Chronological age measures how many years a person has lived, but biological age reflects how well the body is functioning. Biological aging can differ significantly from one person to another depending on factors such as health, lifestyle, and the body’s ability to recover from stress and disease.

To estimate biological age, scientists analyze biomarkers, which are measurable indicators of physiological health over time. These biomarkers are often considered more useful than chronological age for understanding long-term health and potential lifespan.

For this study, researchers used information from 20 biomarkers to calculate participants’ biological age scores. These included measurements such as cholesterol, insulin, and C-reactive protein levels. The data came from the Nutrition for Healthy Living study conducted at the University’s Charles Perkins Centre.

Four Different Diet Plans Tested

The study included 104 participants who were randomly assigned to one of four diets. Each diet provided 14 percent of total energy from protein.

Two diets were omnivorous, with half of the protein coming from animal sources and the remainder from plants. The other two were semi-vegetarian diets, in which 70 percent of the protein came from plant sources.

Within those categories, participants were also assigned either a high-fat, low-carbohydrate diet or a low-fat, high-carbohydrate diet. This created four diet groups: omnivorous high-fat (OHF), omnivorous high-carbohydrate (OHC), semi-vegetarian high-fat (VHF), and semi-vegetarian high-carbohydrate (VHC).

Participants’ BMI (body mass index) ranged from 20-35. All participants were non-smokers, non-vegetarians and had no serious complications (e.g., type-2 diabetes mellitus, cancers, renal or liver disease) or food allergies and/or intolerances.

Which Diet Produced the Biggest Change?

Researchers found that the OHF group, whose diets remained closest to what participants had already been eating before the study, showed no significant change in biological age markers.

However, the other three groups all showed reductions in biological age. The strongest statistical evidence came from the OHC group, which followed an omnivorous diet that was higher in carbohydrates and lower in fat. In that group, 14 percent of energy came from protein, 28-29 percent from fat, and 53 percent from carbohydrates.

Although the results suggest diet may influence biological aging surprisingly quickly, researchers caution that it is still unknown whether these improvements last long term or lead to sustained reductions in biological age.

Researchers Call for Longer Studies

“Longer term dietary changes are needed to assess whether dietary changes alter the risk of age-related diseases,” said Associate Professor Alistair Senior, from the School of Life and Environmental Sciences and the Charles Perkins Centre, who supervised the research.

“It’s too soon to say definitively that specific changes to diet will extend your life. But this research offers an early indication of the potential benefits of dietary changes later in life,” said Dr. Andrews.

“Future research should explore whether these findings extend to other cohorts and whether the changes recorded are sustained or predictive of long-term outcomes.”