A new study from researchers at the University of Sydney in Australia examined how different combinations of fat, carbohydrates, and plant-based protein affected biological age in adults ages 65 to 75.
During the 4-week study, participants who followed lower-fat or more plant-focused diets experienced greater reductions in biological age estimates compared to those eating a more typical high-fat omnivorous diet.
The study is published in Aging Cell.
Diet plays an important role in healthy aging and may influence inflammation, metabolism, and the risk of chronic diseases in older adults.
Scientists are interested in whether certain eating patterns could affect biological age markers tied to overall health.
While chronological age reflects someone’s actual age based on their birth, biological age reflects how well the body is functioning physiologically. Ideally, someone would have a matched or lower biological age (or age gap).
The researchers in the new study analyzed data from 104 older adults participating in the Nutrition for Healthy Living study. The participants were between 65 and 75 years old and were generally healthy.
None of the participants smoked or had major chronic conditions, such as cancer or type 2 diabetes.
The scientists randomly assigned the participants to one of the following four diet groups:
The semi-vegetarian diets emphasized plant-based proteins, while omnivorous diets included more animal-based foods.
All groups consumed 14% of their calories from protein, but the diets otherwise varied in fat and carbohydrate content, with some diets higher in fat and lower in carbohydrates, while others were lower in fat and higher in carbohydrates.
The researchers noted that the carbohydrates in the study primarily came from minimally processed foods rather than refined sugars or ultra-processed carbohydrates.
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Prior to the participants beginning their diet plans, the researchers measured their baseline biomarkers, including biomarkers tied to inflammation (such as C-reactive protein) and cardiovascular health, to determine their biological age scores.
Once the participants started their eating plans, they continued for 4 weeks, and then the researchers checked their biomarkers again.
After comparing biomarker data before and after the dietary intervention, the researchers found that the omnivorous/high-fat group showed little change in biological age markers after the 4-week period.
The study authors noted that the diets for this group were “most like participants’ baseline diets.” However, the other three groups experienced reductions in biological age estimates overall.
The omnivorous/high-carbohydrate group, which focused on reducing dietary fat while emphasizing complex carbohydrates, had the most significant improvement in biomarker data.
Both of the semi-vegetarian groups (semi-vegetarian/high-fat and semi-vegetarian/high-carbohydrate) showed improvements in multiple biological age markers, but they were not as statistically significant compared to the omnivorous/high-carbohydrate group.
While the study findings indicate that these dietary changes may contribute to a rapid change in biological aging, it is not clear whether this would hold up in the long term since the study only lasted for 4 weeks.
The researchers said the biological age changes observed in the study may reflect temporary physiological responses to dietary changes rather than lasting changes to the aging process itself.
“It is difficult to distinguish whether the observed changes reflect the immediate impact of nutritional inputs on integrated physiological systems or a systematic improvement in ageing-related health,” the study authors wrote.
Dung Trinh, MD, internist of MemorialCare Medical Group and Chief Medical Officer of Healthy Brain Clinic, spoke with Medical News Today about the findings.
Trinh said the findings suggest that the body’s metabolic and inflammatory systems may respond quickly to dietary changes, but cautioned against interpreting the results as proof that diet can reverse aging.
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“Short-term improvements in biological age markers are encouraging, but not definitive,” Trinh said, adding that the biomarkers are better viewed as “a physiologic snapshot” more so than evidence of long-term benefits.
When asked whether the study findings support older adults eating a higher-carb diet, Trinh emphasized that the study should not be interpreted as support for eating more processed carbohydrates but for focusing on macronutrients and higher-quality food.
“Diet quality and macronutrient context matter,” explained Trinh. “Carbohydrates from vegetables, legumes, fruits, intact grains, and fiber-rich foods are very different from carbohydrates from sugary beverages, pastries, and refined snacks.”
Trinh hopes to see a longer trial, of at least 6 to 12 months, to determine whether the health benefits found in the study hold up over a longer period of time.
Claire Burum, RD, a Doctify-verified dietitian based in Australia, also spoke with MNT about the study.
Burum called the findings “promising,” but cautioned that short-term improvements in biological age markers should not be confused with proof of slower aging or longer lifespan.
“Biological age markers estimate health and aging risk rather than directly measuring outcomes like mortality,” Burum said, adding that the study still reinforces the idea that “biological aging is responsive to dietary intervention.”
Burum also emphasized that the study does not suggest people should simply eat more carbohydrates.
“The practical takeaway is not ‘eat more carbs,’ but to prioritize high-quality, minimally processed carbohydrates within an overall balanced diet.”
– Claire Burum, RD
She added that the strongest evidence for healthy aging still supports diets rich in fruits, vegetables, legumes, whole grains, nuts, and minimally processed foods.
