Maintaining a single dietary practicefor over 20 years could help 'slow down' ageing in the brain, new research reveals. Scientists believe this long-term eating pattern could reduce several typically expected 'metabolic alterations', some of which are linked to Alzheimer's disease.

The new study, led by Boston University in the US, studied 10 male monkeys, which were split into two key groups. The first of these was required to eat a 'normal', balanced diet, while the other consumed approximately 30% fewer calories for the remainder of their lives.

Once all monkeys had passed away naturally, scientists then proceeded to analyse their brain matter using single-nuclei RNA sequencing. Overall, results showed that calorie-restricted brain cells were notably more metabolically healthy and functional than those from monkeys which had maintained 'normal' diets.

While these findings are limited to animals, experts generally believe that monkey brains share significant similarities with those of humans, particularly in their fundamental structure and connectivity. The study team now believes their findings could support the idea that long-term dietary interventions can influence the course of brain ageing at a cellular level.

Corresponding author Ana Vitantonio, a fifth-year PhD student, said: "While calorie restriction is a well-established intervention that can slow biological ageing and may reduce age-related metabolic alterations in shorter-lived experimental models, this study provides rare, long-term evidence that calorie restriction may also protect against brain ageing in more complex species."

Professor Tara L. Moore, a co-author of the study also added: "This is important because these cellular alterations could have implications that are relevant to cognition and learning. In other words, dietary habits may influence brain health and eating fewer calories may slow some aspects of brain ageing when implemented long term."

The new research builds upon a wealth of other studies and expert insights regarding the potential benefits of calorie restriction. In Okinawa, Japan, one of the world's six 'Blue Zones', many residents also reportedly practice an '80% trick', which is believed to contribute to their notably long lifespans.

This trick simply involves having one small meal in the late afternoon or early evening each day, and eating only until they are 80% full - hence the name of the hack. Dr Deborah Lee, a GP at Dr Fox Pharmacy, previously told the Mirror: "Imagine what 80% of your meal would look like, and aim to leave 20% behind.

"Calorie restriction is believed to slow the ageing process. Eating less lowers the metabolic rate. With less metabolic processes underway, less oxidation is taking place. Oxidative stress probably underpins the development of many of the chronic diseases we see today – heart disease, cancer, type-2 diabetes and dementia."

Dr Lee also claimed that taking your time to eat slowly can help with maintaining the 80% rule, too. This is supported by science, with a 2012 study highlighting that slower eating is linked to greater satisfaction and reduced hunger between meals.

She continued: "Nutritionists believe that when you look at your plate, if you eat mindfully, eating slowly and chewing every mouthful thoroughly, you can feel satisfied by eating only 80% of that is on your plate.

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"The diet has many benefits. You don’t have to count calories, and no foods are absolutely forbidden. It can fit in with your work and social schedule. You are still eating large amounts of healthy foods and getting good nutrition."

Despite this, certain foods are certainly recommended over others when it comes to calorie restriction. Many Blue Zone residents opt for diets brimming with plant-based items and whole foods as opposed to processed products.

Dr Lee added at the time: "We need to encourage the population to ditch processed foods – ready meals, takeaways, fried food, cakes, biscuits, puddings, desserts and fizzy drinks - and cook from scratch using fresh, healthy ingredients."