Does quality diet and waist-hip ratio affect brain connectivity and cognitive function?

With the increasing popularity of fast food and unhealthy diets, there is a rise in the prevalence of diabetes, cardiovascular disease, and obesity which are all known risk factors for dementia. The World Health Organization (WHO) guidelines recommend weight management and a balanced diet with high plant-based intake (e.g. Mediterranean diet) to reduce the risk of dementia. 

AIM

The aim of the research was to find if a higher quality diet and lower waist-hip ratio (WHR) throughout midlife are associated with more favorable indicators of hippocampal function and structural connectivity in the brain w.r.t. cognitive function. 

METHODS

A longitudinal study of 10 308 participants established in 1985 by the University College of London was followed up for over 30 years through 13 study waves. 

WHR was measured at waves - 3 (1991-1994), 5 (1997-1999), 7 (2002-2004), 9 (2007-2009) and 11 (2012-2013). Diet was assessed at wave 3,5 and 7. 

A random subset of participants also received brain MRI scans and cognitive tests as part of the Whitehall II Imaging sub study conducted from 2012-2016 at the University of Oxford. 

Cognitive tests were performed at the time of MRI scans to assess working memory, fluency, and executive function. 

Only those participants who had 

1. Information on their diet at least 1 of 3 previous waves
2. WHR information from 2 of 5 previous waves and 
3. Good quality structural resting-state fMRI and Diffusion tensor imaging (DTI) scans

The final sample included:

• 664 participants for analyses of WHR and 512 participants for analyses of diet quality – were sent for fMRI analysis.
• 657 participants for WHR and 506 for diet quality were sent for DTI analysis. 

RESULTS

This study showed that 

1. Higher quality diet and lower WHR in midlife were associated with structural and functional connectivity of the hippocampus at older age.
2. Lower WHR in midlife was associated with better working memory and executive function in later life. It was observed that white matter integrity was directly associated with individual-level improvements in diet quality from middle to older age. 
3. Higher abdominal fat in midlife was also associated with worse cognitive performance in older age across several cognitive domains including fluency, episodic memory, working memory, and executive function. Previous studies in the past have shown similar results. 

Discussion 

Prevailing theories of pathways from lifestyle risk factors to cognitive health via brain microstructures are supported by this study such as:

• Higher fractional anisotropy in widespread tracts
• Lower mean diffusivity in the optic radiation and the superior parietal lobe
• Lower axial diffusivity in the superior longitudinal fasciculus 

The above-mentioned structures of the brain have been implicated as markers of microstructural damage in dementia. 

LIMITATIONS

• Dietary data collected via self-report questionnaire could have been open to errors.
• The Alternative Healthy Eating Index 2010 (AHEI – 2010) may not be adapted to the dietary habits of all populations.
• The authors suggest using more robust MRI harmonized procedures for future studies instead of adjusted scanner sites using binary measures used in this study. 
• The cohort in this study was predominantly white British males with high education levels, susceptible to survival bias, hence generally healthier than the standard U.K. population limiting the generalizability of study findings. 

CONCLUSION 

The authors concluded that measures of diet and abdominal fat in midlife were associated with hippocampal function and white matter connectivity in later life. 

“Higher WHR in midlife was associated with poorer working memory and executive function in older age, and this association was partially mediated by white matter diffusivity.” 

CLINICAL IMPLICATION

Diet improvisation and management of central obesity in midlife may help achieve beneficial outcomes for brain and cognitive health in later/older age. 

SOURCE: This article was published on March 12, 2025, on the JAMA open network titled “Association of diet and waist-to-hip ratio with brain connectivity and memory in aging”. 

(https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2831324) 

AUTHOR: : Daria E. A. Jensen, DPhil, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstrasse 1a, 04103 Leipzig, Germany.