Just four weeks of eating differently could make your body biologically younger, Australian research finds

What if your body could start ageing more slowly in less than a month, simply by changing what you eat?

That is the intriguing early finding from new University of Sydney research, which found that people aged 65 to 75 who made specific dietary changes showed measurable signs of reduced biological age in just four weeks.

The study, published this week in the journal Aging Cell, is one of the first to show that short-term dietary changes can shift the biological markers of ageing in older adults – and the results appeared regardless of whether participants cut back on fat or switched from animal to plant-based protein.

What is biological age, and why does it matter?

Your chronological age – the number on your birthday cake – ticks forward the same for everyone. But your biological age is different. It reflects how well your body is actually functioning and how resilient it is to illness and stress, and it can be estimated by measuring a range of health indicators in the blood.

For this study, researchers tracked 20 different biomarkers – including cholesterol, insulin and C-reactive protein (a marker of inflammation) – to calculate each participant’s biological age score.

The idea is that two people who are both 70 years old can have very different biological ages depending on their health. Improving that biological age is considered a meaningful sign of better long-term health outcomes.

What the research found

The study involved 104 Australians aged 65 to 75, conducted through the University of Sydney’s Charles Perkins Centre as part of the Nutrition for Healthy Living study. Participants were assigned to one of four diets, all providing the same proportion of protein (14 per cent of daily energy), but varying in whether that protein came mainly from animal or plant sources, and whether the diet was higher in fat or higher in carbohydrates.

Three of the four groups showed a reduction in biological age over four weeks. The exception was the group whose diet most closely resembled what they were already eating – an omnivorous diet higher in fat and lower in carbohydrates.

The strongest result, with the highest statistical confidence, came from the group eating an omnivorous diet that was higher in carbohydrates and lower in fat – roughly 53 per cent carbohydrates, 28 to 29 per cent fat and 14 per cent protein. Those who shifted toward more plant-based protein also showed improvement.

Lead researcher Dr Caitlin Andrews said it is too early to make definitive claims, but the findings are encouraging.

“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,” she said.

What this means in practice

The two dietary shifts associated with biological age improvement – eating less fat, and getting more protein from plant sources such as legumes, nuts and grains rather than meat — are changes that align with general healthy eating advice already recommended by most health guidelines.

In practical terms, that could mean swapping some red meat for fish or legumes a few nights a week, increasing the amount of vegetables, wholegrains and fibre on your plate, or simply reducing how much fat you consume overall.

Associate Professor Alistair Senior, who supervised the research, was measured in his assessment of what the results mean right now.

“Longer-term dietary changes are needed to assess whether dietary changes alter the risk of age-related diseases,” he said.

The researchers have called for longer trials to determine whether the biological age improvements hold up over time and whether they actually translate into a reduced risk of conditions like heart disease, type 2 diabetes or cognitive decline.

Still, the finding that meaningful change appeared in just four weeks suggests that the body’s response to diet may be faster than many people assume — good news for anyone wondering whether it is too late to benefit from eating better.