Switching to a diet full of fresh veggies and low in processed foods could do wonders for your brain's biological age, new research shows.

According to the international team of researchers who ran the study, eating a Mediterranean diet rich in vegetables, seafood, and whole grains – or even just following dietary guidelines – appears to slow the signs of accelerated brain aging typically seen in obesity with as little as 1 percent loss in body weight.

Brain scans taken after 18 months showed the participants' brain age appearing almost nine months younger than expected, compared to estimates of their brain's chronological age.

Like the participants in the clinical trial, you might not feel as old as the years you've lived, or perhaps your body feels like it's aging faster than you are – this is the difference between biological and chronological age.

Either way, research shows your body's biological age is much more than a feeling: Signs of biological aging can be found dotted along your DNA, etched onto the ends of your chromosomes, or as this study suggests, in the loosening connections of your brain.

While a growing body of research suggests that biological aging brought on by stressful events could be reversible, this new study shows that improving your diet may be one of the simplest options to improving body condition, irrespective of the years.

In the study, the researchers imaged the brains of 102 participants who were taking part in a larger clinical trial conducted at one workplace in Israel. Brain scans were taken once before the trial began and again after 18 months, along with a battery of tests of liver function, cholesterol levels, and body weight.

Groups ate one of three diets: a Mediterranean diet with lots of nuts, fish, and chicken instead of red meat; a Mediterranean diet with a few added extras such as green tea for the polyphenols; or a diet based on healthy dietary guidelines.

Estimates of brain age were based on an algorithm that had been trained on brain scans from a separate cohort of nearly 300 people, with the model accurately predicting age from measures of brain connectivity.

On average, people in the trial lost around 2.3 kilograms. For every 1 percent of body weight lost after following a set diet or health guidelines, the participants' brains appeared almost nine months younger than their chronological age, the researchers found.

Whether changes in brain connectivity actually translate to improvements in brain function is still a big unknown. The brain is a complex web of flexible connections we're only just beginning to map out, though a recent review hints at the Mediterranean diet having a positive effect on memory in older people.

Signs of slowed brain aging were also associated with lower levels of liver fat and improved lipid profile but again, these changes could be superficial or short-lived.

"Our study highlights the importance of a healthy lifestyle, including lower consumption of processed food, sweets, and beverages, in maintaining brain health," says lead author and neuroscientist Gidon Levakov of Ben-Gurion University of the Negev in Israel.

That might be sound advice and although these findings are from a clinical trial where participants were randomly 'prescribed' a diet to follow, there are a few other limitations worth digesting.

Most of the participants were men, and they filled out online surveys about their diet and lifestyle habits, meaning the data may be skewed by what they could recall or chose to report.

And it's not all about food: participants' activity levels at work were taken into account; they also received a free gym membership as part of the trial, so exercise was a factor too.

What's more, past research has uncovered how the good fats of a Mediterranean diet work on a cellular level. But it has also exposed clear discrepancies in who reaps the health benefits of a diet rich in Mediterranean staples.

People with well-paying jobs and higher education who could afford to buy lots of fish and whole grains saw greater improvements in cardiovascular health than those on low incomes – even if their adherence to the diet was the same.

The study has been published in eLife.