Study: A change in diet for just one month lowered biological age in adults over 65. What did they eat?

Biological age could be altered with diet, a new Australian study suggests. In adults over 65, one month of dietary changes was associated with measurable improvements in markers of aging.

Adults aged 65 to 75 who reduced either dietary fat or animal protein for a month decreased their estimated biological age, according to a study published in the journal Aging Cell.

The research was conducted at the University of Sydney, Australia, on 104 volunteers and used a mathematical calculation that combines 20 blood markers into a single score. The results indicate that dietary changes can rapidly influence biomarkers of aging, even at advanced ages. The authors point out, however, that the study has limitations and that the results remain preliminary.ite and that the results remain preliminary.

Biological and chronological age do not always coincide. Two people who turned 70 in the same month may have different values ​​of blood pressure, cholesterol, blood sugar and inflammation. The variations are related to genes, eating habits, sleep, movement and the environment in which they live. Longevity researchers estimate biological age using biomarkers in the blood, which are considered more accurate indicators of the body's actual condition than simply the date in the bulletin.

The team led by Caitlin Andrews, a researcher at the University of Sydney, used data from a randomized trial called Nutrition for Healthy Living, conducted at the Charles Perkins Centre. The volunteers were between 65 and 75 years old, did not smoke or have diabetes, cancer or liver disease, and had a body mass index between 20 and 35. The 104 participants were randomly divided into four groups and their meals were prepared and delivered daily for 28 days.

The four diets tested

All four types of diets contained the same amount of protein: 14% of the total number of calories for a day. But two diets were omnivorous, with half of the protein from animal sources and half from plant sources, and the other two were semi-vegetarian, with 70% of the protein coming from plants. Within each group, volunteers received either more fat and less carbohydrate, or vice versa.

Two omnivorous variants

The first diet was omnivorous and high in fat. This was used as a benchmark as it most closely resembled the participants' usual diet before the study. It provided approximately 37-41% of calories from fat and 41-43% from carbohydrates. Proteins came from both animal and plant sources. It was the closest variation to the Western diet described by the authors, with more processed foods, refined sugars and saturated fats.

The second diet was omnivorous, but high in carbohydrates and lower in fat. About 53% of calories came from carbohydrates, and fat made up only 28-29% of daily intake. It should be noted that the sources of carbohydrates were not sweets, white bread or pastries, but minimally processed foods. The authors pointed out that the diet included more whole grains, legumes, fruits and vegetables, i.e. foods rich in fiber. The participants also continued to eat animal products, but the diet was lower in fat and higher in fiber than their usual diet.

Two semi-vegetarian options

The third diet was semi-vegetarian and high-fat. In this group, the main change was not the reduction of fat, but the source of protein. About 70% of the protein came from plants, and animal products were limited, not completely eliminated. Participants were getting more legumes, whole grains and other plant sources of protein, but the diet remained high in fat, close to the high-fat omnivorous version. Even so, this diet reduced estimated biological age in some analyses, a sign that replacing some animal protein with plant protein can rapidly influence metabolic and inflammatory biomarkers.

The fourth diet was semi-vegetarian and high in carbohydrates. It combines more plant protein and more complex carbohydrates with lower fat intake. Participants consumed more vegetables, fruits, whole grains and legumes, such as beans, lentils or chickpeas, and animal products were present in smaller amounts.

The diet associated with the clearest reduction in estimated biological age

To identify biological age based on the analyses, the researchers used the Klemera-Doubal method. The technique integrates 20 biomarkers and clinical parameters into a single score, validated in previous large cohort studies as a predictor of disease and death risk. Among the indicators analyzed were blood pressure, total cholesterol, insulin, blood sugar and C-reactive protein, a marker of systemic inflammation.

The high-fat omnivorous diet, which was closest to the volunteers' pre-study habits, did not produce noticeable changes in the biological profiles. The other three diets decreased the estimated biological age. The most statistically significant reduction occurred in the high-carbohydrate omnivorous diet group. Similar but not always statistically significant reductions were observed in the semi-vegetarian groups.

“It is too early to say with certainty that certain dietary changes will prolong life. But this research is an early indication of the potential benefits of dietary changes in older age,” said Caitlin Andrews.

The volunteers ate enough to maintain their weight. The study did not impose any calorie restriction, although calorie reduction has long been studied in relation to aging. The observed differences were related to the type of food, not the amount of energy consumed.

What exactly does biological age mean?

Unlike chronological age, which increases uniformly with each birthday, biological age reflects how your tissues and organs are functioning at that time. A 72-year-old retiree who walks daily, eats vegetables and fish, and sleeps well may have tests comparable to those of a 65-year-old. Likewise, someone who smokes, drinks frequently, and is overweight may reach 50 with a prematurely tired cardiovascular system.

In recent years, researchers have also begun to measure biological age through so-called epigenetic clocks. They look at chemical changes to DNA, particularly methylation, a process that doesn't change the genetic code but influences how genes are turned on or off. Based on these signals, statistical models can estimate whether tissues appear younger or older than their chronological age would indicate.

What brings this diet closer to the Mediterranean model

The combination that produced the best results in the Australian study closely resembles the Mediterranean dietary pattern: more vegetables, legumes, fruit, whole grains, fish, vegetable oils and less red or processed meat.

The researchers do not encourage giving up meat altogether. The semi-vegetarian versions in the study still contained 30% animal protein. Specifically, such a change may mean more meals based on legumes and whole grains and, when animal products are eaten, smaller portions or lower-fat options such as fish

A simple example would be a day where breakfast includes plain yogurt with oatmeal, nuts and fruit, lunch – a vegetable soup with beans or lentils and a slice of wholemeal bread, and dinner – a portion of baked fish with vegetables and a salad with olive oil.

On another day, meat can be completely absent: hummus with vegetables and wholemeal bread in the morning, lentil stew for lunch, then a hearty salad with chickpeas, tomatoes, cucumbers, peppers, greens and a few seeds – for dinner.

Long-term studies are needed

“Longer-term dietary changes are needed to assess whether dietary changes influence the risk of age-related diseases,” said Alistair Senior, one of the study's authors.

In addition, the trial included healthy individuals without major chronic diseases. People with diabetes, cardiovascular disease, or other metabolic problems might respond differently to the same dietary changes. The Klemera-Doubal score is also useful in research on large populations, where it can be associated with risk of disease and mortality, but does not automatically show what will happen to each individual.

The study also has limitations in size and duration. The 104 participants represent a relatively small sample, and one month is too short a period for firm conclusions about aging and longevity. But what the research shows, the authors say, is that a composite biological age score can respond visibly to dietary changes in just 28 days, including in healthy people over 65.