Not wrinkles on face or gray in hair. Clock in question is hidden in signals carried by your blood, metabolism, and cardiovascular system. In new study, some older adults ate differently for just four weeks – and estimates of their biological age shifted several years younger.
Even more surprising, strongest change appeared in group eating more carbohydrates and less fat, challenging familiar idea that carbs must always be cut. So did these people really become younger in a month? Or did clock measure something more fleeting?
Study, published in Aging Cell, offers intriguing but cautious answer.
104 Adults 65-75 – Every Meal Prepared And Delivered For 4 Weeks
Researchers at University of Sydney analyzed data from 104 adults aged 65 to 75 who participated in Nutrition for Healthy Living trial. Every meal they ate for four weeks was prepared and delivered by researchers. Participants did not count calories and could eat as much as they wanted from supplied menus.
They were randomly assigned to four groups, meaning they did not choose which diet to follow. Two diets included both plant and animal foods, with half their protein coming from animal sources. Two were semi-vegetarian, with 70 percent of protein coming from plants. Each type was split again. One menu contained more fat and fewer carbohydrates; other contained less fat and more carbohydrates. In every diet, protein supplied 14 percent of total energy.
Before and after trial, researchers calculated participants’ biological age.
Chronological age records time since birth. Biological age reflects how old body appears based on measurements such as blood pressure, blood sugar, cholesterol, inflammation, and body composition. Team used Klemera-Doubal Method, or KDM, to combine age-related clinical measurements into single estimate. Two versions incorporated seven or 15 markers, including cholesterol, glucose, insulin, blood pressure, waist circumference, and body mass index.
Results – High-Carb Low-Fat Whole Food Diet Dropped Estimate 3.5-4.1 Years
High-fat diet containing animal foods, which most closely resembled participants’ usual diets, produced no meaningful change in biological-age estimates.
Estimates fell in other three groups.
Strongest evidence came from group eating both plant and animal foods, but with less fat and more carbohydrates.
Depending on KDM calculation, this group’s biological-age estimate was around 3.5 to 4.1 years lower than that of high-fat comparison group after baseline differences were taken into account.
But that does not mean four years vanished from anyone’s life. Study co-author Alistair Senior says that calling participants biologically younger would slightly overstate finding. Instead, diets gave them “the biomarker profile of a younger person,” he says.
And “high carbohydrate” did not mean menu of cake, candy, and white bread. Carbohydrates came mainly from whole, minimally processed foods. Researchers warn that findings should not be extended to diets rich in refined sugars or simple carbohydrates. Groups with lower age estimates also consumed more fiber, less fat, and less animal protein than they usually did. Senior says saturated fat intake, which distinguished high-fat omnivorous diet from other three, may explain difference.
Does Clock Measure Real Aging Or Temporary Response?
There is another mystery. Biological-age measures can react quickly to temporary changes. Previous research has found stress can push biological age upward before measurements fall again during recovery. Diet can rapidly alter blood sugar, cholesterol, insulin, inflammation, and blood pressure. Because these feed into KDM calculation, clock may have moved even if deeper trajectory of aging did not. That leaves study’s central question unresolved: Did participants begin aging more slowly, or did bodies simply respond positively to four weeks of different food?
Trial cannot separate those possibilities. It lasted only four weeks and involved small, relatively healthy group of older Australians. Participants already had younger-than-expected physiological profiles at beginning. Researchers also do not know whether changes continued once supplied meals ended, reduced age-related disease risk, or helped anyone live longer.
Senior says much longer studies must track participants’ risk of age-related disease. If diet gives someone both biomarker profile and disease risk of younger person, “functionally what else do you want?” he asks. Still, findings offer tantalizing clue. Body’s apparent age may not be carved in stone. It may behave like dashboard, moving as metabolism, inflammation, and cardiovascular health respond to what we eat.
Related: Scientists Are Trying to Define What ‘Reversing Aging’ Really Means
Four weeks of controlled meals did not prove aging had been reversed. But they showed how quickly body’s age-related signals can answer when menu changes.
Study was published in Aging Cell.
Q&A
Q: Can diet really turn back your biological clock in 4 weeks?
A: University of Sydney study of 104 adults 65-75 found high-carb low-fat whole food diet lowered KDM biological-age estimate by 3.5-4.1 years vs high-fat animal diet after 4 weeks of prepared meals.
Q: Which diet lowered biological age most?
A: Omnivore diet with less fat more carbs from whole minimally processed foods, 14% protein, more fiber less saturated fat less animal protein than usual, showed strongest evidence, not cake candy white bread.
Q: Did people actually become younger?
A: No, co-author Alistair Senior says they got biomarker profile of younger person – blood pressure, glucose, cholesterol, insulin, waist, BMI – KDM clock reacts quickly to temporary changes, not proof slower aging or longer life.
FAQ
1. What is Nutrition for Healthy Living trial?
Randomized trial in Australia of 104 adults 65-75 where every meal for 4 weeks was prepared and delivered, free eating, 4 groups: omnivore vs semi-vegetarian 70% plant protein, each high-fat low-carb vs low-fat high-carb, all 14% energy protein.
2. What is Klemera-Doubal Method KDM?
Method combining 7 or 15 age-related clinical markers like cholesterol, glucose, insulin, blood pressure, waist, BMI into single biological age estimate; chronological age is time since birth.
3. Why high-carb worked if carbs usually cut?
High-carb here meant whole minimally processed carbs with more fiber less fat less animal protein, likely lower saturated fat explaining difference; not refined sugars.
4. What are limitations?
Only 4 weeks, small relatively healthy older Australians with younger-than-expected profiles at start, cannot separate temporary biomarker response vs true slower aging, unknown if changes persisted, reduced disease risk or longevity.
5. What needs to happen next?
Much longer studies tracking age-related disease risk, whether biomarker profile change translates to functionally younger disease risk, as Senior notes.
Disclaimer; This article for informational purposes only and does not constitute medical advice
