Being overweight or obese has long been linked to poor heart health, but could it also impair your thinking?
New research out of Canada suggests it very well might.
Working with thousands of young, middle aged, and older adults, the new study highlights what appears to be fat’s direct harm on one’s ability to think quickly, with rising body fat levels linked to diminishing mental health returns.
“Our findings are intriguing, because we show that [fat], as it increases, not only increases traditional cardiovascular risk factors like diabetes and high blood pressure, but also influences cognitive [mental skill] test scores,” said study lead author Dr. Sonia Anand, is who is head of the Population Health Research Institute at McMaster University in Hamilton, Ontario.
That does not, however, mean that every aspect of one’s capacity to think is vulnerable, Anand stressed.
For example, Anand and her team did not find any link between rising levels of excess fat and impaired memory or vocabulary skills.
But they did identify a fat-induced slow-down in “processing speed” – meaning the time it takes to absorb, understand, and react to sights, sounds, or movement.
Between 2010 and 2018, nearly 9,200 adults aged 30 to 75 (average age 58) were enrolled in the study. None had a prior history of heart disease.
All underwent brain scans (MRIs) to pinpoint potential blood vessel injuries. Almost all had total body fat measurements, while about three-quarters completed assessments of belly fat as well.
To gauge their thinking, the participants completed two tests that examined attention skills, concentration, short-term memory, eye-hand speed and co-ordination, and the ability to learn and/or calculate new information.
Women carried more overall body fat than the men, though guys tended to pack on more excess weight around their stomachs. About two-thirds of the men had what the authors characterized as “central obesity,” compared with just over one-third of the women.
Still, carrying excess weight – regardless of where – was found to pose a threat to heart health, with higher overall body fat and abdominal fat driving up both high blood pressure and diabetes risk.
Excess body fat also appeared to boost the risk for brain injury, including lesions or the kind of markers that indicate a history of unrecognized (“silent”) strokes.
And Anand and her colleagues noted that poorer heart health has long been known to put a person’s ability to think clearly and quickly at risk.
But this study went one step further, identifying what appears to be excess fat’s direct damage to thinking, even after taking into account heart health, brain status, and education.
In fact, the researchers identified a direct more-is-more dynamic: as body fat rose, people processed information more slowly, as if their brains had aged.
Specifically, the team noted that a participant’s ability to think “aged” up by about one year for every 9% increase in overall body fat.
Anand said it remains unclear whether a fat-induced loss of processing speed is permanent or if slimming down might reverse the situation. Either way, avoidance is key.
“The signs do point to the importance of staying active, eating a healthy diet, and preventing extra weight gain,” said Lona Sandon, program director of the department of clinical nutrition at UT Southwestern Medical Center in Dallas.
At the same time, Sandon cautioned that this study does not prove cause and effect, even if the likelihood of a link between excess body fat and worsening mental health “is probable.”