The Cognitive Functions of Youth With Obesity: A Meta-Analysis

This meta-analysis examined the associations between obesity and performance across seven cognitive domains (inhibition, cognitive flexibility, working memory, verbal fluency, planning, attention, and intelligence quotient [IQ]) in youth under 18 years. Developmental stage (school-aged children vs. adolescents) and sample sex composition examined as moderators. Evidence on executive function in youth with comorbid obesity and attention-deficit/hyperactivity disorder (ADHD) was synthesized qualitatively.

Following PRISMA guidelines, 22 studies comparing youth with obesity to normal-weight peers were included. Effect sizes (Hedges' g) were pooled using a random-effects model. Subgroup analyses compared school-aged children and adolescents; meta-regression examined age and proportion of female participants as study-level moderators.

Youth with obesity performed significantly worse than normal-weight peers on inhibition (g⁺ = -0.193), cognitive flexibility (g⁺ = -0.499), working memory (g⁺ = -0.652), verbal fluency (g⁺ = -0.420), attention (g⁺ = -0.526), and IQ (g⁺ = -0.288); planning could not be estimated. School-aged children showed deficits on inhibition, working memory, and attention; adolescents on working memory and attention only. Between-subgroup tests were non-significant for all domains (p ≥ 0.26), so developmental differences should be interpreted with caution. Meta-regression showed that a higher proportion of female participants in a study sample, a study-level characteristic rather than an individual-level effect, was associated with larger working memory deficits (p = 0.002); age did not moderate any domain. Two ADHD-comorbidity studies received qualitative synthesis only.

Obesity is associated with poorer cognitive performance in youth across several domains, with sex composition of the study sample emerging as a moderator of the working memory finding; differences between school-aged children and adolescents were not significant and should be interpreted cautiously. Substantial heterogeneity, predominantly observational designs, inconsistent BMI criteria, and limited ADHD-stratified data constrain causal inference. Future studies should standardize weight definitions, report age- and ADHD-stratified data, and consider bidirectional pathways.