Diet quality and abdominal fat in midlife are linked to brain health in older age

A recent study published in JAMA Network Open suggests that maintaining a high-quality diet and managing abdominal fat during midlife may help preserve brain health and cognitive function in later years. Researchers found that individuals who followed healthier diets and had lower waist-to-hip ratios between the ages of 48 and 70 showed stronger brain connectivity and better cognitive performance as they aged. These findings highlight the potential for lifestyle changes in middle age to reduce the risk of cognitive decline and dementia.

Unhealthy eating habits and obesity have long been linked to chronic conditions such as diabetes and heart disease, which are also known risk factors for dementia. While prior research has examined how specific nutrients affect brain function, few studies have explored the long-term effects of overall diet quality and abdominal fat on brain connectivity and memory. The hippocampus, a brain region essential for memory, is particularly sensitive to lifestyle-related changes, but evidence regarding its connectivity with other brain areas remains limited.

The new study aimed to address these gaps by investigating whether diet quality and waist-to-hip ratio in midlife, as well as changes in these factors over time, were associated with brain structure, brain function, and cognitive abilities in older age. By analyzing long-term data, the researchers hoped to clarify whether lifestyle factors influence brain health during the transition from middle to late adulthood.

“In the context of the global obesity pandemic (with approximately 43% of adults and 20% of children worldwide classified as overweight), improving metabolic health and dietary quality during midlife is essential for brain health and cognition in later life,” explained study author Daria E. A. Jensen, a postdoctoral fellow at the University Medical Center Leipzig and the Max Planck Institute for Human Cognitive and Brain Sciences, and visiting researcher at the University of Oxford.

“This aligns with the World Health Organization’s guidelines, which emphasise a balanced diet and effective weight management as key strategies for preventing dementia. This study aimed to address gaps in existing research by examining the long-term effects of overall diet quality and waist-to-hip ratio (as a measure for abdominal fat) on brain connectivity and cognitive function.”

The researchers used data from the Whitehall II Study, a long-term health study of British civil servants that began in 1985. Participants’ waist and hip measurements were taken at five different time points over 21 years, while their diet quality was assessed using a validated food questionnaire at three of those time points. The study focused on 664 participants for the waist-to-hip ratio analysis and 512 for the diet quality analysis, all of whom later underwent MRI brain scans and cognitive tests.

The researchers measured diet quality using the Alternative Healthy Eating Index-2010, a scoring system that reflects adherence to a balanced diet rich in fruits, vegetables, whole grains, and healthy fats. They assessed brain connectivity using MRI scans, examining both structural integrity (using diffusion tensor imaging) and functional connections in the hippocampus (using resting-state fMRI). Cognitive function was evaluated through a series of memory, executive function, and processing speed tests.

The study found that individuals who maintained a higher diet quality throughout midlife had stronger functional connectivity in the hippocampus, particularly with brain regions involved in visual processing and coordination. This suggests that better diet quality supports neural connections that are important for memory and cognitive function.

Additionally, participants who improved their diet quality over time showed better structural integrity in several key white matter pathways, including the corticospinal tract and superior thalamic radiation. These pathways are essential for communication between different brain regions and are often affected in aging and neurodegenerative diseases.

In contrast, a higher waist-to-hip ratio in midlife was associated with widespread disruptions in white matter integrity, particularly in tracts connected to the hippocampus. Individuals with higher waist-to-hip ratios performed worse on memory and executive function tests in older age. The study also found that these cognitive deficits were partly mediated by changes in white matter structure, suggesting that abdominal fat may contribute to brain aging by damaging neural pathways.

“The key takeaway from our study is that maintaining a high-quality diet and managing waist-to-hip ratio during midlife are crucial for supporting brain health and cognitive function in later life,” Jensen told PsyPost. “These lifestyle choices can have long-lasting impacts, potentially reducing the risk of cognitive decline and dementia.”

Interestingly, while diet quality was linked to brain connectivity and structure, it did not directly correlate with cognitive test performance. In contrast, waist-to-hip ratio had a clear impact on cognitive abilities, likely due to its influence on white matter health. This suggests that excess abdominal fat may accelerate cognitive decline by impairing the brain’s structural integrity.

“It was surprising to see the strong association between waist-to-hip ratio and cognitive performance, mediated by changes in white matter connectivity,” Jensen said. “This highlights the significant impact of central obesity on brain health, which is not commonly emphasized in discussions about cognitive maintenance.”

As with all research, there are some limitations to consider. The participants were predominantly male and had higher education levels than the general population, which may limit the applicability of the findings to a broader audience. Additionally, diet quality was self-reported, which can introduce inaccuracies in measuring food intake. The study also did not account for other lifestyle factors such as physical activity or genetic predispositions that may influence brain health.

“While our study highlights significant associations between diet, waist-to-hip ratio, and brain health, it’s important to note that these findings are correlational and do not establish causation,” Jensen noted. “However, studies on people living with obesity showed that bariatric surgery for weight loss may lead to brain structure reorganisation at long-term follow-up (e.g. Prehn et al., 2020). With our longitudinal study design, we could show the long-term impact of body composition and diet in midlife onto brain organization and cognition later in life.”

Future research should explore whether specific dietary patterns, such as the Mediterranean diet, have stronger effects on brain connectivity. Further studies could also investigate whether reducing abdominal fat through targeted interventions leads to measurable improvements in cognitive function.

“My long-term goals include exploring the mechanisms linking diet and obesity to brain health, particularly the role of the gut microbiome,” Jensen said. “I also aim to investigate specific eating behaviours and decision-making processes to refine strategies for preventing cognitive decline through lifestyle modifications.”

The results of this study highlight midlife as a key period for lifestyle interventions aimed at preserving brain health. Encouraging individuals to adopt a healthier diet and manage their waist-to-hip ratio between the ages of 48 and 70 could have lasting benefits.

“I would like to emphasize the critical role of early lifestyle interventions in the prevention of cognitive decline,” Jensen concluded. “Our findings underscore the importance for medical doctors to advocate for healthier dietary habits and effective management of central obesity during midlife. By doing so, healthcare professionals can play a pivotal role in guiding patients towards lifestyle choices that significantly influence their cognitive health trajectory, ultimately reducing the risk of dementia and enhancing quality of life in older age.”

The study, “Association of Diet and Waist-to-Hip Ratio With Brain Connectivity and Memory in Aging,” was authored by Daria E. A. Jensen, Klaus P. Ebmeier, Tasnime Akbaraly, Michelle G. Jansen, Archana Singh-Manoux, Mika Kivimäki, Enikő Zsoldos, Miriam C. Klein-Flügge, and Sana Suri.