A new study has found that greater body fat is a risk factor for reduced cognitive function, such as processing speed, in adults. 

Even when the researchers took into account cardiovascular risk factors (such as diabetes or high blood pressure) or vascular brain injury, the association between body fat and lower cognitive scores remained.

This suggests other not yet confirmed pathways that linked excess body fat to reduced cognitive function. 

In the study, 9,166 participants were measured by bioelectrical impedance analysis to assess their total body fat.  

As well, 6,733 of the participants underwent magnetic resonance imaging (MRI) to measure abdominal fat packed around the organs known as visceral fat. The MRI also assessed vascular brain injury — areas in the brain affected by reduced blood flow. 

The results were published this week in JAMA Network Open. 

“Our results suggest that strategies to prevent or reduce having too much body fat may preserve cognitive function,” says lead author Sonia Anand, a professor of medicine at McMaster’s Michael G. DeGroote School of Medicine, and a vascular medicine specialist at Hamilton Health Sciences. She is also a senior scientist of the Population Health Research Institute of McMaster and HHS.  

“The effect of increased body fat persisted even after adjusting for its effect on increasing cardiovascular risk factors like diabetes and high blood pressure, as well as vascular brain injury,” she says, “which should prompt researchers to investigate which other pathways may link excess fat to reduced cognitive function.” 

Preserving cognitive function is one of the best ways to prevent dementia in old age, says co-author Eric Smith, a neurologist, scientist and an associate professor of clinical neurosciences at the University of Calgary.

“This study suggests that one of the ways that good nutrition and physical activity prevent dementia may be by maintaining healthy weight and body fat percentage.” 

Smith is head of the brain core lab for the two population cohorts used for this new analysis — the Canadian Alliance for Healthy Hearts and Minds (CAHHM) and PURE Mind, a sub-study of the large, international Prospective Urban Rural Epidemiological (PURE) study. 

The participants were in the age range of 30 to 75, with an average age of about 58. Just over 56 per cent were women; they all lived in either Canada or Poland. The majority were of White European origin, with about 16 per cent being from other ethnic backgrounds. Individuals with known cardiovascular disease were excluded. 

The CAHHM study was funded by the Canadian Partnership Against Cancer, Heart and Stroke Foundation of Canada, and Canadian Institutes of Health Research (CIHR). The PURE-Mind study was funded from multiple sources including the Population Health Research Institute, CIHR, and Heart and Stroke Foundation.