Want a sharper mind in your golden years? Start by trimming your waistline. 

A new study found that diet quality and waist-to-hip ratio in midlife are directly linked to brain health and cognitive function as we get older. 

“This message is alarming in light of the obesity pandemic.” Dr. Sharmili Edwin Thanarajah, a neurologist at Goethe University Frankfurt who wasn’t involved in the study, wrote in an accompanying editorial. 

Changes in the Western diet have played a major role in driving America’s obesity crisis, which is linked to chronic conditions such as type 2 diabetes, cardiovascular disease and high blood pressure. It’s also the leading modifiable risk factor for dementia.

More than six million Americans are currently living with the memory-robbing disease, a figure expected to reach 12 million by 2060 without intervention. Experts say these projections highlight the urgent need to prevent or slow dementia’s onset — starting with lifestyle changes like a healthier diet and regular exercise.

Previous studies have suggested that midlife is a critical window for cognitive health interventions, but little was known about how long-term adherence to a high quality diet affects brain health as we age.

To investigate the potential link, researchers used data from the Whitehall II Study, a 30-year longitudinal study tracking over 10,000 participants. They monitored the waist and hip measurements of 664 middle-aged British civil servants over a 21-year period.

At the same time, 512 participants filled out detailed diet questionnaires covering 11 factors, including fruits, vegetables, whole grains, fats and sugary drinks.

When the participants hit their 70s, the scientists took brain scans and tested their cognitive performance. They found that those with lower hip-to-waist radio at the start of the study had better working memory, executive function and overall cognitive performance later on. 

Participants who stuck to healthier diets in midlife also showed better brain function, especially in regions responsible for learning, memory and how different parts of the brain communicate with each other.

But don’t panic if you haven’t been eating well. Researchers found that participants who improved their diets over the course of the study saw improvements in their brain health — particularly when it came to dementia and aging.

“If you want to do something for your brain health, it is not too late to do something now, but the earlier you start, the better,” Dr. Daria E. A. Jensen, an author of the study and postdoctoral researcher at Oxford University, told BBC Science Focus. 

The researchers said that interventions aimed at improving diet and managing central obesity might be most effective for people aged 48 to 70, leading to the best outcomes for brain and cognitive health in later years.

“Their findings call for increased prevention strategies during midlife to combat the increasing number of individuals experiencing cognitive impairments,” Edwin Thanarajah said. 

She emphasized that improvements in diet quality — rather than simply reducing waist-to-hip ratio — were linked to better brain health later in life. She also cited research showing that even brief exposure to an unhealthy, fat- and sugar-rich diet can negatively affect brain function in healthy individuals.

“It is crucial to integrate dietary guidelines into public health policies,” Edwin Thanarajah said. “Such an integration should be an independent and essential strategy for protecting brain health, alongside the evaluation of metabolic and cardiovascular risk factors.”

Jensen and her team noted some study limitations, including the fact that the participants were mostly white British men, highly educated and generally healthier than the broader UK population.