Can changing what you eat make your body biologically younger? Scientists studied 104 older adults for 4 weeks and found a surprising clue

Getting older is unavoidable. But the number of birthdays a person has celebrated does not always tell the full story about their health.

Two people who are both 70 years old can have very different levels of inflammation, metabolic health and cardiovascular fitness. One may remain active and healthy, while the other may experience several age-related problems.

This difference is part of what scientists mean by biological age.


Unlike chronological age, biological age is an estimate based on measurable features of the body. Researchers use biomarkers to assess processes linked to health and aging, including metabolism, inflammation and cardiovascular function.

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These estimates can help scientists understand how the body changes over time. However, biological age is not a perfect measurement, and it cannot predict exactly how long someone will live.

Scientists studying 104 older adults found that three groups showed reductions in estimated biological age after following different diets for just four weeks. The strongest statistical evidence came from participants who ate an omnivorous diet containing less fat and more carbohydrates.

The findings, published in Aging Cell, offer an interesting glimpse into how quickly the body may respond to changes in nutrition. They also raise a bigger question: can the food we eat actually influence the aging process?

For the University of Sydney study, researchers examined 20 biomarkers to calculate an estimated biological age score. These included cholesterol, insulin and C-reactive protein.

C-reactive protein is a marker commonly used to assess inflammation. Cholesterol and insulin provide information about metabolic and cardiovascular health.

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By bringing these measurements together, the researchers were able to examine whether the participants’ biological age estimates changed after four weeks of dietary intervention.

The study was led by Dr. Caitlin Andrews from the University of Sydney’s School of Life and Environmental Sciences. Associate Professor Alistair Senior supervised the research.

The work was part of the Nutrition for Healthy Living study conducted through the university’s Charles Perkins Centre.

Four diets tested over just 28 days

The researchers wanted to understand whether the balance of nutrients in a person’s diet could influence biological age-related markers.

Rather than comparing a healthy diet with an unhealthy one, they designed four different eating patterns.

Each diet supplied 14% of total energy from protein. The researchers then varied the amount of fat and carbohydrates, as well as the sources of protein.

Two groups followed omnivorous diets, meaning their protein came equally from animal and plant sources. The other two followed semi-vegetarian diets, with 70% of their protein coming from plants.

Within both categories, participants followed either a higher-fat, lower-carbohydrate diet or a lower-fat, higher-carbohydrate diet.

This created four distinct groups.

The omnivorous high-fat group followed a diet higher in fat and lower in carbohydrates. The omnivorous high-carbohydrate group ate less fat and more carbohydrates while continuing to obtain protein from animal and plant sources.

The semi-vegetarian groups followed similar high-fat or high-carbohydrate plans, but most of their protein came from plants.

The participants were aged between 65 and 75. Their BMI ranged from 20 to 35.

Researchers excluded people with serious medical conditions such as type 2 diabetes, cancer, kidney disease and liver disease. Participants were also non-smokers and non-vegetarians.

The study therefore examined a specific group of older adults rather than the entire population.

After four weeks, researchers compared the participants’ biomarker profiles with their measurements taken before the diet began.

The higher-carbohydrate diet produced the strongest signal

The results were not identical across all four groups.

Participants following the omnivorous high-fat diet did not show a meaningful change in their calculated biological age. This group also followed the diet most similar to what participants had been eating before the study began.

The other three groups showed reductions in estimated biological age based on their biomarker profiles.

The strongest statistical evidence appeared in the omnivorous high-carbohydrate group.

Participants in this group consumed approximately 14% of their energy from protein, 28–29% from fat and 53% from carbohydrates.

That does not mean carbohydrates alone were responsible for the changes.

The four diets differed in several ways, including fat levels and protein sources. As a result, the researchers cannot identify one nutrient as the definite cause of the observed differences.

The findings suggest that changing dietary composition may influence some biological age-related markers in older adults.

But the results should not be interpreted as proof that eating more carbohydrates automatically makes the body younger.

The study also did not establish that one particular diet is best for healthy aging.

What makes the research noteworthy is the timeframe. Changes in the biological age estimates appeared after only 28 days, suggesting that some measurable responses to diet may occur faster than many people expect.

Whether those changes are meaningful over the long term remains unanswered.

A lower biological age score is not the same as reversing aging

The phrase “biological age reversal” can make the findings sound more dramatic than they are.

A biological age score is calculated from a set of measurements. If those biomarkers change in a direction associated with younger biological profiles, the estimated score may fall.

That does not necessarily mean the body has become younger in every sense.

The researchers did not show that participants had reversed the aging process, extended their lifespan or become less likely to develop age-related diseases.

They also did not establish whether the changes would remain after participants stopped following their assigned diets.

These limitations are important because biological aging involves many systems throughout the body. A change in cholesterol, insulin or inflammation markers does not capture every aspect of aging.

The study provides information about selected biomarkers, not a complete picture of a person’s health or future lifespan.

Associate Professor Alistair Senior said that longer-term dietary changes would be needed to assess whether diet affects the risk of age-related diseases.

Dr. Andrews also cautioned against claiming that specific dietary changes will extend life.

The researchers want to investigate whether the results can be reproduced in other populations and whether the changes persist over time.

They also hope to determine whether changes in biological age markers can predict meaningful long-term health outcomes.

What the findings mean for older adults

The study adds to scientific interest in the relationship between nutrition and healthy aging.

Diet plays a role in several processes that change with age, including metabolism, inflammation and cardiovascular health. These systems are closely connected to how the body functions over time.

Understanding how different dietary patterns affect them could eventually help researchers develop better approaches to healthy aging.

However, the results do not provide a simple diet plan for everyone over 65.

The strongest statistical evidence came from the omnivorous high-carbohydrate group, while two other modified diets also showed reductions in estimated biological age. The omnivorous high-fat group did not show a meaningful change.

This pattern suggests that the balance of nutrients may matter, but it does not establish that people should simply increase their carbohydrate intake.

Older adults have different nutritional requirements depending on their health, activity levels and existing diet. Adequate protein intake and maintaining muscle health are particularly important considerations when changing eating habits.

A diet that works for one person may not be appropriate for another.

For now, the University of Sydney study offers an early clue that dietary changes may influence biological age-related markers within four weeks.

It does not establish that aging can be permanently reversed through food.

The next step is to find out whether these changes last and whether they translate into better health over months or years.

The researchers’ findings suggest that what we eat may influence how the body functions as it ages. But the question of whether diet can truly turn back the biological clock remains open.

Frequently asked questions

1. Can changing your diet make you biologically younger in four weeks?

The study found reductions in estimated biological age among three of four dietary groups after 28 days. These results were based on changes in biomarkers and do not prove that participants became younger or reversed aging.

2. Which diet showed the strongest results?

The omnivorous high-carbohydrate diet showed the strongest statistical evidence of a reduction in estimated biological age. It provided approximately 14% of energy from protein, 28–29% from fat and 53% from carbohydrates.

3. How many people took part in the University of Sydney study?

The research involved 104 adults aged 65 to 75. Participants were randomly assigned to one of four diets as part of the Nutrition for Healthy Living study.

4. Does the research prove that eating more carbohydrates extends lifespan?

No. The study did not establish that a higher-carbohydrate diet extends life or prevents age-related diseases. Longer-term research is needed to determine whether the observed changes persist and have meaningful health benefits.