Body Mass Index (BMI) categorizes body weight relative to height. Intelligence Quotient (IQ) is a score from standardized cognitive ability tests. Research has explored the relationship between BMI and IQ, and this article examines those findings.
Exploring the Relationship Between BMI and IQ
Scientific studies often reveal an inverse association between BMI and IQ, where higher BMI correlates with lower IQ scores. This pattern is observed across age groups, with a notable correlation in school-age children. A meta-analysis found obese children had an average IQ 5.26 points lower, with verbal IQ 7.73 points lower.
Longitudinal studies support this link, suggesting lower childhood IQ may predict adult obesity. A New Zealand study found participants with lower IQ at age 38 tended to be more obese. Similarly, a British study showed IQ scores at age 7 could predict higher BMI at age 51, with BMI increasing faster after age 16 among those with lower IQ. Intelligence test scores are highest at a BMI of approximately 20 kg/m², declining with higher BMI, and slightly lower in underweight individuals.
Potential Biological and Lifestyle Connections
Links between BMI and cognitive function involve biological and lifestyle factors. Chronic low-grade systemic inflammation, often associated with obesity, can affect brain function and contribute to cognitive decline. Adipose tissue in obese individuals releases immune and metabolic mediators like C-reactive protein (CRP) and interleukin-6 (IL-6), which can cross the blood-brain barrier and promote neuroinflammation.
Metabolic health also plays a role, with insulin resistance and dysregulated glucose metabolism in the brain linking obesity to poorer cognitive performance. Reduced levels of brain-derived neurotrophic factor (BDNF), a protein for neuronal health, are associated with obesity and cognitive deficits. Lifestyle factors, such as diet and physical activity, independently influence both BMI and cognitive abilities. Diets high in fats and sugars, common in Western diets, are linked to chronic inflammation, oxidative stress, and insulin resistance, all negatively impacting brain health.
Interpreting the Findings and Important Considerations
When interpreting the relationship between BMI and IQ, remember that correlation does not imply causation. Many complex factors influence both body weight and cognitive ability. Socioeconomic status is a confounding factor; studies show lower IQ scores are associated with higher BMI, but this relationship is largely mediated by socioeconomic status. Children from ultra-poor households often exhibit lower BMI and IQ scores.
Access to education and parental influence are additional factors impacting both measures. Parental education level, for example, is positively associated with a child’s IQ score. Health conditions, sleep patterns, and physical activity levels also independently affect both BMI and cognitive function. Research indicates an association between BMI and IQ, but this relationship is multifaceted and influenced by interconnected environmental, social, and biological factors.