A Higher Carb Diet May Lower Your Biological Age, New Study Suggests

Some of nutrition’s most reviled macronutrients might be getting an image overhaul, courtesy of a new study. The research, which was conducted by the University of Sydney and ran in the journal Aging Cell, sought to find how much of an impact changing eating habits could have on a person’s biological age. While there is no standardized way to measure biological age, this study looked at, among other things insulin, blood pressure, cholesterol, and more to determine the age of the subjects’ cells. Based on the findings, certain adjustments can do a lot—and in a short amount of time, particularly of the higher-carbohydrate variety.

Biological age has been a big focus in research and armchair health of late. As you may know, biological age is how old your cells and body are; chronological age is the number of years you’ve been alive. Biological age, which is influenced by factors including bodily inflammation and underlying diseases and conditions, has shown up in everything from health trackers to research studies, although its usefulness outside of cocktail conversation is still being explored. You won’t find your family doctor relying on this metric.

To back up, researchers at the University of Sydney recruited 104 adults in their mid-60s and 70s and randomly assigned the participants to follow one of four diets for four weeks. (It’s worth noting the study was small, with only 26 participants per group). Each person was asked to ingest 14% of their total calories from protein while following each diet. Two of the diets were omnivorous—meaning participants ate foods from an equal mix of plant and animal sources—and two were semi-vegetarian, where 70% of the protein came from plant sources. People were then asked to follow a higher-fat, lower-carbohydrate diet, or a lower-fat, higher-carbohydrate diet.

The biggest impact on biological age seemed to be in participants who ate an omnivorous, high-carbohydrate diet. Participants in that group got 14% of their calories from protein, up to 29% of their calories from fat, and 53% from carbohydrates. Per the study, carbohydrates in all diets were “primarily comprised complex carbohydrates, derived from whole, minimally processed sources.”

The omnivorous, high-fat diet, which most closely resembles a Western diet of the four, was the most similar to the way participants had been eating before the study started. (Health-care providers and researchers often use the term “Western diet” to describe a pattern that includes high levels of refined grains, red and processed meats, ultra-processed foods, fried foods, and high-fat dairy products.) That diet contained fewer servings of fruits, vegetables and legumes than the other three, albeit with the same minimally processed carbohydrates. The researchers found no meaningful change in the biological age of those participants after four weeks. But people in the other groups all had reductions in their estimated biological age based on their biomarkers. These are years of estimated biological age, not years of life, so it means the blood results looked like those of a younger person. And the intervention period was relatively short-term, so we can't be certain that the observed shifts reflect real, lasting changes in the rate of aging.

Carbohydrates seem to be coming back into favor elsewhere, too. New research from the Tabriz University of Medical Sciences, published in the European Heart Journal, linked eating up to six servings of whole grains a day (about six slices of whole grain toast) with lower cholesterol, blood sugar, and body weight, all of which can influence biological age.

However, dietitians have some thoughts before you order your next bowl of carbonara in the name of longevity.

Why might the high-carbohydrate diet reduce biological aging?

It’s hard to determine what these biomarker changes mean in terms of actual biological aging in the real world beyond the study. “I wouldn’t necessarily look at this as an age reversal,” says Jessica Cording, RD, registered dietitian and author of The Little Book of Game-Changers. The researchers also wrote in the study that “caution is warranted in interpreting such changes as evidence of biological age reversal.”

Even the study’s researchers are hesitant to apply an actual number of biological years gained based on the findings. "These are years of estimated biological age, not years of life, so it means the blood results looked like those of a younger person,” explains Caitlin J. Andrews, PhD, study co-author and researcher at the University of Sydney's School of Life and Environmental Sciences.

“Eating more carbs may also mean higher intake of fiber from plant foods, but not necessarily,” says Sandra Zhang, RDN, LDN, registered dietitian and nutritionist at the Frances Stern Nutrition Center at Tufts Medical Center. Cording agrees, noting that all carbohydrates are not created equal. “People tend to think of bread, rice, pasta, and sugar as carbs, but they often forget that vegetables, fruit, nuts, seeds, and legumes also have carbohydrates,” she says. These foods offer a wide array of nutrients, including vitamins and polyphenols to support healthy aging, she points out. This particular study focused on high-quality, complex carbohydrates like those Cording listed. “This could be reflecting more whole foods in a person’s diet,” Cording says. “It’s not just about the carbs.”

While dividing up a diet by its macronutrients is a convenient way to categorize an eating routine, Zhang notes that good nutrition is more than just that: “Different types of fats, carbohydrates, fiber, and protein intake can also influence the inflammation process,” she says.

The quality of diet matters, too, according to Dr. Andrews. “The benefits across the study tended to be associated with the diets that moved further away from a typical Western diet toward more minimally processed, whole food diets,” she says.

What the findings mean for a healthy diet

When it comes to diets, variety is key for longevity, Zhang says. That means including different types of fats from animals and plants, and trying to feature a wide range of nutrients on your plate. “Plant-based proteins do carry the benefits of low-fat and high-fiber, but they are not necessarily easily absorbed and complete, especially for the elderly,” Zhang says.

That’s why Cording suggests a balance of plant and animal proteins. “Make room for beans, nuts, and seeds, along with lean meats. There is room for all of it,” she says. “You want an overall diet pattern that gives you a good balance of protein, fats, and carbohydrates.”

People have been wary of carbs for years, but the latest findings suggest there’s a place for this macronutrient—provided you choose wisely. “Foods like vegetables, fruits, legumes, and whole grains tend to be higher in fiber, more filling, and associated with better long-term health than more heavily processed, carbohydrate-rich foods,” Dr. Andrews says. “More broadly, I think there’s a lot to be said for shifting the focus away from restriction and more toward overall dietary quality and balance.”

More conventional wisdom, like limiting ultra-processed foods and excess added sugar, is also important for healthy aging, Cording says. “I tend to recommend a plant-forward Mediterranean-style diet,” she adds. This diet includes a mix of high-quality carbohydrates, like brown rice, lentils, and beans, with up to 60% of calories coming from these sources.

Overall, the findings are a solid reminder that it’s never too late to change your diet. “The researchers saw that short response time; four weeks is nothing,” says Cording. “It reinforces that you don’t need to eat perfectly for years before your body starts to benefit from you making better food choices.”

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