Older adults who shifted the mix of fat, carbohydrates and animal protein on their plates showed signs of a younger biological age after only four weeks, according to a controlled feeding trial published in the journal Aging Cell.
The clearest signal came from a lower-fat, higher-carbohydrate omnivorous diet.
The trial, led by Dr. Caitlin Andrews at the University of Sydney's Charles Perkins Centre, put 104 volunteers aged 65 to 75 on one of four diets and tracked 20 blood markers linked to aging.
What the four diets looked like
Every diet supplied 14 percent of daily energy from protein.
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What changed was the source of the protein and the balance between fat and carbohydrates.
Two groups ate an omnivorous diet, one higher in fat and one higher in carbohydrates.
Two groups ate a semi-vegetarian diet with about 70 percent of their protein from plants, again split into a higher-fat and a higher-carbohydrate version.
The omnivorous high-carbohydrate diet worked out to roughly 14 percent protein, 28 to 29 percent fat and 53 percent carbohydrates.
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For most people that means smaller portions of meat, less butter and oil, and more room on the plate for grains, potatoes, legumes, fruit and vegetables.
Biological age
Biological age is not the number of birthdays on a passport.
It is an estimate of how the body is holding up, built from measurable markers.
In this trial the researchers combined 20 markers, including cholesterol, insulin and C-reactive protein, an indicator of inflammation, into a single score.
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When those markers move in a healthier direction, the estimated biological age falls, even when the calendar has not moved at all.
Three of the four diet groups saw their biological age score edge down.
The lower-fat omnivorous group showed the strongest statistical evidence of a shift.
The higher-fat omnivorous diet, which most closely mirrored what the participants were already eating, produced no meaningful change.
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Why the researchers are cautious
Four weeks is a very short window. The trial measured changes in blood markers, not disease outcomes, and it enrolled a specific group: non-smoking, non-vegetarian Australians aged 65 to 75 with a body mass index between 20 and 35, and no serious illnesses such as type 2 diabetes, cancer, or kidney or liver disease.
"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," Andrews said in the University of Sydney's announcement of the findings.
Her supervisor, Associate Professor Alistair Senior, added that longer term dietary changes are needed to assess whether they alter the risk of age-related diseases.
In practice that means the study points in a direction rather than delivering a prescription, and anyone thinking about a bigger shift in eating pattern, especially those managing a chronic condition or taking medication, should talk to their own doctor first.
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This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.