Illustration by Briana Rengifo; Source images: Getty Images Save Story Save this story Save Story Save this story 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.
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