Scientists from the University of Sydney have discovered that changing diet habits for only four weeks may improve important markers linked to aging in older adults.
The study, published in the journal Aging Cell, found that adults aged between 65 and 75 showed signs of becoming biologically younger after reducing dietary fat or replacing some animal protein with plant-based foods.
Researchers say the findings provide early evidence that the aging process may respond more quickly to diet than many people realize.
The research focused on biological age rather than chronological age. Chronological age simply measures how many birthdays a person has had. Biological age is different because it reflects how healthy and functional the body actually is.
Some people age more slowly than others due to differences in lifestyle, exercise, stress, genetics, sleep, and diet. Scientists believe biological age may provide a better picture of future health risks and overall aging.
To estimate biological age, researchers use biomarkers, which are measurable signals inside the body linked to health and aging. These include markers related to cholesterol, inflammation, blood sugar control, insulin, and immune function.
For this study, the scientists analyzed 20 biomarkers to estimate participants’ biological ages before and after dietary changes.
The study included 104 adults who were generally healthy. None of the participants smoked or had serious diseases such as cancer, severe liver disease, kidney disease, or diabetes.
Participants were randomly assigned to one of four different diets.
Two diets included both animal and plant foods, while the other two were more plant-focused semi-vegetarian diets.
Within these categories, some participants followed high-fat, low-carbohydrate diets, while others followed low-fat, high-carbohydrate diets.
This allowed researchers to compare how different combinations of fat, carbohydrates, and protein sources affected biological aging.
The participants followed their assigned diets for four weeks while researchers monitored changes in their biological age markers.
The results showed clear differences between the groups.
Participants following an omnivorous high-fat diet showed almost no meaningful improvement. Researchers explained that this diet was very similar to what many participants normally ate before joining the study.
However, the other three groups showed reductions in biological age markers after only one month.
The strongest improvements were seen in the group eating an omnivorous diet that was lower in fat and higher in carbohydrates.
In this diet, about 53 percent of total energy came from carbohydrates, while fat intake was reduced to around 28 to 29 percent. Protein intake remained moderate.
Researchers say the findings may suggest that lower-fat eating patterns and greater reliance on plant-based foods could help reduce inflammation and improve metabolic processes associated with aging.
The study also highlights how quickly the body may respond to dietary changes.
Scientists have long known that unhealthy eating contributes to diseases such as heart disease, obesity, diabetes, and some cancers. However, this study suggests that even short-term improvements in diet may rapidly affect measurable aging-related biomarkers.
Still, the researchers emphasize that the study was small and lasted only four weeks.
Dr. Caitlin Andrews, who led the study at the University of Sydney’s School of Life and Environmental Sciences, said the findings should not be interpreted as proof that diet can reverse aging or extend lifespan.
Instead, the research offers an early indication that changing diet later in life may improve biological markers linked to health and aging.
Associate Professor Alistair Senior, who supervised the research, also explained that longer studies are necessary to determine whether these biological changes are maintained over time and whether they truly reduce the risk of age-related diseases.
The researchers also want future studies to investigate whether similar effects occur in younger adults or people with different health conditions.
Experts not involved in the study say the findings are interesting because they support broader evidence showing that diet plays a major role in healthy aging.
Plant-based foods are rich in fiber, vitamins, antioxidants, and other compounds that may help reduce inflammation and support healthy body function.
At the same time, experts warn against overly restrictive diets, especially for older adults who still need enough nutrients and protein to maintain muscle mass and strength.
The study does not suggest that all animal foods are harmful or that carbohydrates are always better than fats. Instead, it highlights the possibility that balanced dietary patterns emphasizing lower fat intake and more plant foods may benefit aging-related health markers.
Overall, the research adds to growing scientific interest in how lifestyle choices may influence the speed of biological aging.
Although much more research is needed, the findings suggest that healthy eating habits may still produce meaningful benefits even later in life.
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The study was published in Aging Cell.
Source: University of Sydney.
