The ‘realistic’ high-carb diet that can reduce your biological age, weight and cholesterol in just weeks: Researchers tested four diets to see if they could really transform you… and found plan that can ‘slow ageing’

Slowing down ageing has been a Holy Grail for centuries, and is very much a focus of modern medicine. But it may not require the latest and most expensive high-tech wizardry, for now researchers believe they have discovered a diet that may help turn back the clock, reducing your biological age.

Even more striking, benefits from the diet can be seen in less than a month.

Indeed, the results of an Australian study, just published in the journal Aging Cell, are fuelling hopes that the closest thing yet to an elixir of youth may not be found in a laboratory or medicine cabinet – but on our dinner plates.

The study looked at what happened to 104 adults aged 65 to 75 put on one of four different diets for four weeks: omnivorous high-fat (OHF), omnivorous high-carbohydrate (OHC), semi-vegetarian high-fat (VHF), or semi-vegetarian high-carbohydrate (VHC).

The menu plans were delivered to the participants and all four diets were largely composed of minimally processed foods, with the carbs from whole foods such as wholegrains, legumes and fruit and veg. These were not weight-loss diets – although most participants lost weight.

At the end of the study, those on the omnivorous high-fat diet showed no change, but the participants in the other three groups reduced their ‘biological age’ – calculated using clinical measurements such as blood pressure and 20 biomarkers including cholesterol, insulin and C-reactive protein, which is linked to inflammation.

But the omnivorous high-carbohydrate diet – where 14 per cent of the calories came from protein, 28 to 29 per cent from fat, and 53 per cent from complex carbohydrates – had the most significant effect. People on this diet finished off, on average, about three and a half years ‘younger’ than they were at the start of the study, compared with those on the OHF diet. (This compared with three years ‘younger’ with the other semi-vegetarian diets.)

In both omnivorous diets, half of the protein was from animal sources and the rest from plants. In the semi-vegetarian diets, 70 per cent of the protein was from plants.

‘Dairy was in all four diets,’ said Dr Caitlin Andrews, a scientist from the University of Sydney’s School of Life and Environmental Sciences, who led the study.

‘Muesli with yogurt was a standard breakfast across the groups. Semi-veg involved swapping red meat and poultry for legumes, soy, nuts and seeds – not cutting animal foods completely.’ For instance, tikka masala was made with either chicken or tofu, and casserole made with either lamb or beans.

Dr Andrews said they wanted the diets to be realistic. ‘Debates about diet and ageing often get framed as either/or – so it’s plant v animal protein, carbs v fat and so on.

‘In reality, people eat both at once, so the trial was set up in a way that meant we could look at protein sources and the fat-to-carb balance together and see whether they interact to create a beneficial effect.’

Participants lost an average of 4lb over the four weeks, and 94 per cent lost some weight.

Dr Andrews told Good Health: ‘Weight loss was seen across all groups, including the omnivorous higher-fat group, which showed no meaningful change in biological age, so weight loss alone doesn’t explain the differences between diets.’

While it’s not clear why those on a low-fat, high-carb diet did the best, the researchers were surprised by the speed of change. 

‘Four weeks is short, and I don’t think we necessarily expected to see a shift in that window,’ says Dr Andrews. ‘That said, some of the individual biomarkers – like C-reactive protein – are known to respond to diet within a relatively short timeframe.’

One factor is the diets moved further away from a typical Western pattern toward more fibre-rich whole foods.

Dr Thomas Holland, a physician scientist at Rush University in Chicago in the US, who is investigating the impact of lifestyle modifications on chronic diseases of ageing, said the findings from the University of Sydney backed up previous research. 

For example, a large-scale study published in Nature Medicine last year, which followed more than 100,000 participants for up to 30 years, found that people who had healthy, long lives had a higher intake of fruits, vegetables, whole grains, unsaturated fats, nuts, legumes and low-fat dairy products.

Those who reported higher intakes of salt, trans fats (formed when liquid fats are made solid, such as in some margarines), sugary beverages and red or processed meats (or both) were less likely to reach 70.

Dr Holland told Good Health: ‘This makes complete sense to me because the diets that improved had several things in common, including lower saturated and trans fats and higher fibre and fruit and vegetables.’ 

He adds that fibre, for instance, can help steady blood sugar levels, and improve the gut microbiome. Fruit and vegetables also provide a wide range of vitamins, minerals and compounds that can reduce inflammation and oxidative stress – where damaging molecules known as free radicals damage cells. Lowering saturated fat can improve LDL cholesterol and vascular health.

‘These findings also fit well with what we see in the MIND, Mediterranean, and DASH diets, which emphasise many of these same foods while limiting high-fat dairy, butter, fried foods, sweets, and red or processed meats.

‘So I think the bigger takeaway is not one particular food or nutrient – but a high-fibre, minimally processed, nutrient-dense dietary pattern.’

Many studies have shown that healthy eating goes hand in hand with slower biological ageing – including a new study published in Nature Communications.

Researchers in Germany looked at ten different diets, including the Mediterranean diet and the Nordic diet (which focuses on plenty of root vegetables, wholegrains and seafood). Blood samples were checked for markers of DNA methylation, a type of change affecting which genes are turned on or off, that can be used to measure biological age.

Across the board, the diets which were judged to be healthy because they contained plenty of fresh fruit and vegetables and healthy oils – with low amounts of processed food and saturated fats – were associated with slower biological ageing. 

Meanwhile, eating too much processed food can speed up the ageing process, in particular driving a process called cellular senescence, when ageing cells become ‘zombies’ and stop dividing but release inflammatory signals.

As Dr Holland explains: ‘Diets high in added sugars, refined carbohydrates, saturated fats, and low in fibre can contribute to metabolic dysfunction [such as type 2 diabetes and obesity] and drive oxidative stress.’

‘Senescent cells can release inflammatory signals that affect surrounding tissue, contributing to chronic inflammation and preventing organs and skin healing and regenerating.’

More studies are needed to show long-term benefits of dietary changes, however.

The University of Sydney study is not yet conclusive about whether the benefits are temporary or permanent.

Dr Andrews said: ‘Our findings reinforce the idea that healthier overall dietary patterns may support healthier ageing over time – and that small, realistic and sustainable improvements to overall diet quality may still have meaningful effects on health as we get older.’

Time to eat more strawberries?

Fisetin, a compound in strawberries, can destroy damaged or ageing cells, which accumulate in tissue as we get older causing inflammation and damage, according to a 2024 study in the journal Mechanisms of Ageing and Development.

Strawberries also contain pelargonidin, a compound thought to help reduce the rate of cognitive decline and risk of developing Alzheimer’s dementia.

But Dr Thomas Holland, a US expert on lifestyle and ageing, says it’s not as simple as eating more strawberries.

‘There are several foods that can be thought of as “super” foods, but, from a general perspective, ageing is too complex for one food to be the “magic pill”.

‘It’s the diversity of foods that have a more impactful influence over healthy ageing.’