Exploring the complex link between obesity and intelligence: Evidence from systematic review, updated meta-analysis,...

Area of Science:

• Public Health
• Neuroscience
• Genetics

Background:

• Obesity is a significant public health issue linked to numerous comorbidities.
• The relationship between obesity and cognitive function, including intelligence quotient (IQ), is complex and warrants investigation.
• Previous research suggests a bidirectional link between body mass index (BMI) and IQ.

Approach:

• A comprehensive analysis was conducted, integrating a systematic review, meta-analysis, and Mendelian randomization (MR).
• Data were systematically extracted from Medline and Embase databases for studies published since June 22, 2009.
• MR analysis utilized genetic databases like GWAS and GIANT to explore potential causal links between BMI and IQ.

Key Points:

• The systematic review (34 studies) and meta-analysis (17 studies) revealed a significant negative correlation between obesity and IQ, particularly in school-age children (mean difference -5.26).
• Verbal IQ also showed a significant negative association with BMI in school-age children (mean difference -7.73).
• Mendelian randomization analysis did not find a significant causal relationship between BMI and IQ in either childhood or adulthood.

Conclusions:

• A notable correlation exists between higher BMI and reduced IQ, especially in school-aged children.
• Mendelian randomization suggests the causal link between BMI and IQ might be weaker than observational studies indicate.
• Future large-scale cohort studies are recommended to explore confounding factors and elucidate the BMI-IQ relationship.