Most of us accept that our bodies grow a little older every year, and that there is not much we can do about the number on the calendar. But what if the age your blood tests reveal could start to shift in just a few weeks?
- A 2026 University of Sydney trial found that older adults who ate less fat or less animal protein for four weeks showed a younger "biological age" in their blood markers.
- The clearest result came from a lower-fat, higher-carbohydrate whole-food diet, with 53 percent of energy from carbohydrates.
- The group whose diet stayed closest to their usual eating habits showed no meaningful change.
- Biological age was estimated from 20 health markers, including cholesterol, insulin and an inflammation marker called C-reactive protein.
- The researchers call the findings early; longer studies are needed to see whether they lower disease risk.
Yes, changing what you eat may lower your biological age, at least in the short term. In a randomised trial published in Aging Cell in 2026, researchers at the University of Sydney gave 104 adults aged 65 to 75 one of four diets for four weeks. Three of the four diets lowered the participants' biological age score, and the most reliable improvement came from a diet lower in fat and higher in carbohydrates. The team is careful to call this an early signal, not proof that food can turn back the clock.
What Is Biological Age?
Your chronological age is simply how many years you have lived. Your biological age tries to capture how well your body is actually holding up. In this study, the researchers used a well-known scoring method called the Klemera-Doubal Method, which combines 20 blood and health markers, including cholesterol, insulin and C-reactive protein, into a single number. That score has been linked with illness and death rates in large population studies, which is why scientists use it as a rough guide to how fast someone is ageing.
How the Sydney Diet Trial Worked
The study, led by Dr Caitlin Andrews of the University's Charles Perkins Centre and School of Life and Environmental Sciences, was part of the Nutrition for Healthy Living study. Participants were healthy, non-smoking adults aged 65 to 75. For four weeks, all their meals and snacks were supplied by a meal delivery company, so the researchers knew exactly what everyone ate.
Every diet gave 14 percent of its energy from protein. What changed was where that protein came from and how the rest of the calories were split:
- Omnivorous diets: half the protein from animal foods, half from plants.
- Semi-vegetarian diets: 70 percent of the protein from plants.
- High-fat versions: roughly 37 to 41 percent of energy from fat.
- High-carbohydrate versions: 53 percent of energy from carbohydrates and 28 to 29 percent from fat.
What the Results Showed
The omnivorous high-fat group, whose diet was closest to what participants normally ate, showed no meaningful change in biological age. The other three groups all moved in a younger direction. The omnivorous high-carbohydrate group showed the clearest drop, measured with the highest statistical confidence. The two semi-vegetarian diets showed similar reductions, though not all of them reached statistical significance.
Dr Andrews described the work as "an early indication of the potential benefits of dietary changes later in life," while stressing that it is too soon to say diet changes will extend anyone's life.
Why Whole Foods May Matter More Than One Nutrient
An earlier paper from the same trial, published in Aging Cell in 2024, adds useful context. When participants moved from their usual Australian diet to the study's whole-food menus, rich in fruit, vegetables and dietary fibre, their blood pressure, cholesterol and insulin improved across all four groups. Levels of short-chain fatty acids, helpful compounds made when gut bacteria break down fibre, also went up. The more plant-based diets gave an extra drop in diastolic blood pressure.
Put simply, eating less processed food and more fibre seemed to do much of the work. It also explains why "high-carbohydrate" here does not mean more sugar or white bread. The carbohydrates came as part of a balanced, whole-food plan.
What This Means for an Indian Plate
The good news for Indian households is that a traditional thali already leans in this direction: dal and legumes for plant protein, whole grains and millets like ragi and jowar, seasonal sabzi, and modest amounts of ghee. The gap for many of us lies in refined flour, fried snacks and packaged sweets that have slowly crept into daily meals.
A few simple swaps can bring your plate closer to what the study tested:
- Get more of your protein from dal, chana, rajma and paneer, with meat as a side rather than the centre of the meal.
- Choose whole grains and millets over maida.
- Keep fried and heavy, fatty foods occasional rather than daily.
- Snack on fruit, nuts, seeds and whole-grain foods instead of biscuits and namkeen.
The Honest Caveats
This was a short, four-week study in a small group of healthy Australians aged 65 to 75. A lower biological age score after one month may reflect how quickly the body responds to food, rather than a real change in how fast a person is ageing. The authors themselves say longer trials are needed to learn whether these gains last and whether they lower the risk of heart disease, diabetes or other age-related conditions. If you live with a health condition, speak with your doctor before making major changes to your diet.
If you are looking for an easy whole-grain snack to replace the afternoon biscuit, our iHTF Multi Grain Ladoo brings five grains and nuts together in one wholesome bite.
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Frequently Asked Questions
1. What is biological age and how is it different from your real age?
Biological age is an estimate of how old your body seems based on health markers such as cholesterol, blood sugar, insulin and inflammation, rather than the number of birthdays you have had. Two people born in the same year can have very different biological ages depending on diet, activity, sleep and genetics.
2. Can changing your diet really lower your biological age?
Early evidence says it may. In a 2026 University of Sydney trial, adults aged 65 to 75 who ate less fat or less animal protein for four weeks showed a younger biomarker profile. The researchers stress this is preliminary, and longer studies are needed to show whether it lowers disease risk or extends life.
3. Are carbohydrates bad for older adults?
Not necessarily. In the Sydney trial, the diet with the clearest biological age benefit got 53 percent of its energy from carbohydrates, within a whole-food menu rich in fruit, vegetables and fibre. The quality of carbohydrates matters, so fibre-rich whole grains, millets and fruit are a better choice than refined flour and added sugar.
4. How quickly can diet changes improve health markers?
Some health markers can shift within weeks. In the Sydney trial, older adults who switched to a whole-food diet for just four weeks saw improvements in blood pressure, cholesterol and insulin, whichever diet they followed. Keeping these changes going for months and years is what is most likely to bring lasting benefits.
