Four Week Diet Shift Lowers Biological Age Markers In Older Adults
A four-week diet change lowered a composite biological age score in older adults, according to a study of 104 Australians aged 65 to 75 published in Aging Cell.
Researchers at the University of Sydney randomly assigned 104 adults aged 65 to 75, with BMI between 20 and 35, non-smokers without diabetes, cancer, or kidney or liver disease, to one of four diets for 4 weeks. Every diet supplied 14 percent of energy from protein. Two diets were omnivorous (half animal protein) and two were semi-vegetarian (70 percent plant protein), each split into a higher-fat, lower-carbohydrate version or a lower-fat, higher-carbohydrate version. The omnivorous high-carbohydrate group ate 14 percent protein, 28 to 29 percent fat, and 53 percent carbohydrate. Biological age was calculated from 20 biomarkers, including cholesterol, insulin, and C-reactive protein (CRP), a blood marker of inflammation. Three of the four groups showed a lower calculated biological age; the omnivorous high-fat group, the diet closest to what participants ate before the study, showed no meaningful change. The strongest statistical evidence for a lower biological age appeared in the omnivorous high-carbohydrate group. The published summary does not report the actual size of the biological age change in years or percent.
Omnivorous High-Carbohydrate Diet Macronutrient Breakdown Over 4 Weeks
The authors note that reducing dietary fat, animal protein, or both may influence aging-related biomarkers over a short period. Cholesterol, insulin, and CRP all shift in response to how much fat and animal protein a person eats, and each factors into how the composite biological age score is calculated, so a change in diet composition can move the score within weeks even before body weight changes much.
The trial ran 4 weeks, so there is no data on whether the lower biological age score persists or lowers the risk of age-related disease. The study reports directional results rather than the exact size of the biological age shift, and funding and conflicts of interest were not reported in the available record.
Data Panel
- Who
- 104 adults aged 65 to 75, BMI 20 to 35, non-smokers, non-vegetarians, without type 2 diabetes, cancer, or kidney or liver disease
- Design
- Randomized controlled trial, 4 diet groups (omnivorous high-fat, omnivorous high-carbohydrate, semi-vegetarian high-fat, semi-vegetarian high-carbohydrate), 4 weeks, all diets 14 percent protein
- Dose
- Omnivorous high-carbohydrate diet: 14 percent protein, 28 to 29 percent fat, 53 percent carbohydrate over 4 weeks
- Primary result
- 3 of 4 diet groups (omnivorous high-carbohydrate, semi-vegetarian high-fat, semi-vegetarian high-carbohydrate) showed a lower composite biological age score from 20 biomarkers after 4 weeks; omnivorous high-fat group showed no meaningful change; absolute change in the biological age score not reported
- Secondary
- Composite score included cholesterol, insulin, and C-reactive protein (CRP); strongest statistical evidence for a lower biological age appeared in the omnivorous high-carbohydrate group
- Funding / conflicts
- Not reported
Dr. Axe's Take
A four-week diet change moving calculated biological age markers is a meaningful signal, not proof of slower aging. Cholesterol, fasting insulin, and CRP, the markers driving this result, respond quickly to a shift away from animal fat and toward plant protein and complex carbohydrates like lentils, quinoa, and sweet potato. I would not wait for a longer trial to test this on myself. Cut back red meat and processed animal fat for a few weeks, add more plant-based protein, and get a basic panel, cholesterol, fasting insulin, and CRP, before and after so you can see your own numbers move rather than guess.
— Dr. Axe