September 22, 2026, 4:14 pm | Read time: 2 minutes
Can the right diet rejuvenate the body? A new study from Australia offers at least an intriguing hint: After just four weeks, older individuals showed significantly improved age markers. Surprisingly, the best results didn’t come from a low-carb diet but from one with more high-quality carbohydrates and less fat.
Besides actual age, there is the so-called biological age. It is based on health metrics such as blood pressure, blood sugar, cholesterol, BMI, or waist circumference and is meant to indicate how “old” the body is from a medical perspective.
Researchers at the University of Sydney studied 104 people between the ages of 65 and 75. All participants received all their meals delivered for four weeks and were randomly assigned to one of four dietary plans. The study compared higher-fat and higher-carbohydrate meals–each with either meat-based or plant-based protein sources.1
The Surprising Results
The most significant improvements were seen in participants on a diet with less fat and more carbohydrates. Their biological age was calculated to be about 3.5 to 4.1 years younger than that of the high-fat group.
However, the carbohydrate-rich foods were not white bread or sweets but fiber-rich, minimally processed whole foods. Depending on the diet group, participants consumed significantly more fiber, less fat, or more plant-based instead of animal-based proteins.
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Does Diet Really Make Us Younger?
The researchers don’t go that far. The participants were not actually biologically several years younger. Rather, their blood and health metrics showed the profile of younger individuals. Since such markers can change in a short time, it remains unclear whether the diet affects the aging process long-term or just temporarily improves the metrics.
Conclusion
The study does not prove a rejuvenation cure. However, it shows that important age markers can improve within just a few weeks through diet. Particularly interesting: The best results were not from a low-carb diet but from a fiber-rich diet with more high-quality carbohydrates and less fat.
Since the study lasted only four weeks and all meals were provided, the results mainly show how quickly blood and metabolic metrics respond to healthier food. Whether this also slows down the actual aging process in the long term will need to be shown by longer studies.