Carbohydrates are often blamed in weight loss discussions however low carbohydrate diets have become increasingly popular in helping us control our weight and improve our metabolic health. However increasing our carbohydrate intake from the correct food sources may actually help improve our age related biomarkers. A new study from the University of Sydney, published in the journal Aging Cell, has found that older adults following certain dietary patterns showed improvements in their biological-age estimates after just four weeks. The strongest results were seen among participants who followed an omnivorous diet that was lower in fat and higher in carbohydrates. The findings challenge the idea that reducing carbohydrates is always better for health. However, there is an important distinction: researchers were not encouraging participants to eat more sugar, refined flour or processed foods. Their findings point towards a diet built around high-quality, minimally processed foods. The study also does not establish that people can permanently reverse ageing through dietary changes. Instead, it suggests that certain food choices may influence health markers used to estimate biological age.
What Did The University Of Sydney Study Find?
Published in Aging Cell in 2026, the research analysed data from 104 adults aged 65 to 75 who participated in the Nutrition for Healthy Living study. Participants were randomly assigned to one of four dietary patterns for four weeks. These diets differed in their fat and carbohydrate content, as well as the sources of dietary protein. All four diets provided 14 per cent of their total energy from protein. The researchers compared:
- An omnivorous, high-fat diet.
- An omnivorous, high-carbohydrate diet.
- A semi-vegetarian, high-fat diet.
- A semi-vegetarian, high-carbohydrate diet.
The strongest evidence of improvement came from the omnivorous, high-carbohydrate group. Its diet provided approximately 53 per cent of energy from carbohydrates, 28 to 29 per cent from fat and 14 per cent from protein. The high-fat omnivorous group, whose diet was closest to what participants had been eating before the intervention, showed no meaningful change in its biological-age estimate. The other three groups showed reductions in the estimated age of their biomarker profiles, although the statistical strength of the results varied. The difference between the high-carbohydrate omnivorous group and the high-fat comparison group was estimated at approximately 3.5 to 4 years, depending on the biological-age calculation used. This is an encouraging finding, but it should not be interpreted as participants literally becoming four years younger in a month.
What Does Biological Age Mean?
Chronological age refers to the number of years a person has lived. Biological age, on the other hand, attempts to estimate how the body is functioning relative to what might be expected at a particular age. Two people who are both 70 years old may have very different health profiles. One may have better blood pressure, blood sugar regulation and cholesterol levels, while the other may have several metabolic risk factors. Researchers use combinations of health measurements, known as biomarkers, to estimate biological age. In this study, they used the Klemera-Doubal Method (KDM), which combines multiple clinical measurements to generate an estimate of physiological ageing. The researchers considered markers including cholesterol, insulin and C-reactive protein, a blood marker associated with inflammation. The analysis used combinations of seven and 15 biomarkers to calculate biological-age estimates. A lower estimated biological age suggests that the measured health profile has become more favourable. However, these markers can respond to short-term changes in diet and other aspects of health. A four-week improvement does not prove that the underlying ageing process has permanently slowed down.
Does Eating More Carbohydrates Help Slow Ageing?
The study raises an interesting question about the role of carbohydrates in healthy ageing. However, the quality of carbohydrates matters considerably. The higher-carbohydrate diet in the research was not based on sugary drinks, sweets, refined flour or highly processed snacks. It focused on complex, minimally processed carbohydrate sources that can also provide dietary fibre and other nutrients. These include:
1. Whole grains: Oats, barley, quinoa and brown rice provide carbohydrates along with fibre and other nutrients.
2. Legumes: Beans, lentils and chickpeas offer carbohydrates, plant protein and dietary fibre.
3. Fruits: Whole fruits provide natural carbohydrates along with vitamins, minerals and fibre.
4. Vegetables: Vegetables contribute fibre and a range of micronutrients that support overall health.
These foods can form part of a balanced eating pattern and may support better metabolic health. Their fibre content can also help regulate digestion and contribute to healthier blood glucose responses. However, the study does not establish that carbohydrates themselves are an anti-ageing treatment. The results may reflect the combined effects of changing the overall balance of fat, carbohydrates and food sources in the diet.
Why Did The Higher-Carbohydrate Group Show Better Results?
The researchers found that the omnivorous, higher-carbohydrate group had the strongest statistical evidence of improvement compared with the high-fat omnivorous group. One possible explanation is that changing the balance of macronutrients and food sources influenced several metabolic and inflammatory markers measured in the study. However, the research was not designed to establish exactly which food or biological mechanism produced the improvement. It also examined a relatively small group of older adults over a short period.
The findings therefore cannot establish that a higher-carbohydrate diet will have the same effect on younger adults, people with diabetes or those living with other chronic conditions. It is also worth noting that the other two dietary groups showed improvements in their estimated biological-age profiles. This suggests that the findings are not simply a case of carbohydrates being universally better than fats.
Can You Reverse Biological Ageing In Four Weeks?
The short answer is that the study does not prove this. The researchers measured changes in a composite biomarker-based estimate over four weeks. These changes suggest that certain physiological markers can respond relatively quickly to dietary interventions. However, a lower biological-age estimate does not necessarily mean that a person has reversed cellular ageing, reduced their lifespan-related risks or gained additional years of life. The researchers have also emphasised the need for longer-term studies to determine whether these changes persist and whether they translate into a lower risk of age-related conditions. The study included adults aged 65 to 75 who were relatively healthy. Participants with serious health complications such as type 2 diabetes, cancer, kidney disease or liver disease were excluded. The results should therefore not be generalised to every older adult.
Should You Start Eating More Carbohydrates?
The findings are not a reason to suddenly increase carbohydrate intake or abandon a diet recommended by your doctor. Instead, they offer another reason to focus on the quality of food rather than treating an entire macronutrient group as unhealthy. Include whole grains, vegetables, fruits and legumes in your meals. Limit refined carbohydrates, sugary drinks and highly processed foods. Maintain a balanced intake of protein and healthy fats, and consider your individual energy requirements and health conditions. People with diabetes, insulin resistance or other metabolic conditions should discuss major dietary changes with their healthcare provider or a registered dietitian. The right carbohydrate intake can differ considerably between individuals.
The University of Sydney study adds to growing research into how dietary patterns may influence healthy ageing. It found that older adults following a lower-fat, higher-carbohydrate omnivorous diet showed the strongest improvement in biological-age estimates after four weeks. But the message is not to eat more carbohydrates indiscriminately. The quality of those carbohydrates, the overall balance of the diet and an individual's health status all matter.
Most importantly, improved biological-age markers are not proof of permanent age reversal or a longer lifespan. Larger and longer-term studies are needed to understand whether these short-term changes can translate into meaningful health benefits as people grow older.
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