Cognitive performance in young and middle-aged adults with obesity: a systematic literature review

<p>ObjectiveThis systematic review synthesizes longitudinal evidence on associations between obesity and cognitive performance in early or middle adulthood aged 18 to 64. MethodsA comprehensive search of PubMed, PsycINFO, and Web of Science identified prospective studies comparing adults with obesity to those of normal weight and assessing cognitive performance, using validated cognitive tests. Risk of bias was evaluated using ROBINS-E, and findings were synthesized narratively.ResultsAmong a total of 4,871 studies, 4 met the inclusion criteria. Three studies evaluated global cognitive performance in middle-aged adults. Two studies reported poorer cognitive performance in individuals with midlife obesity and a more rapid decline in cognitive performance over 10 years in those who were metabolically unhealthy. One study found no association. Long-term obesity was also associated with lower overall cognitive performance in middle age. Executive performance appeared to be associated with obesity. Research on memory was mixed, as two studies found a negative association with obesity, while two found no association. Methodological weaknesses included imprecise exposure measurements and inadequate adjustment for confounding factors.ConclusionsThe available evidence is too sparse, heterogeneous, and methodologically uncertain to establish a clinically meaningful independent association between obesity and cognitive performance before age 65. Future prospective studies should include cognitive assessment at baseline and repeated follow-up, report standardized effect estimates, use domain-specific cognitive outcomes, address confounding a priori, and assess central adiposity and metabolic health alongside BMI, particularly in younger adults.PROSPERO registration: CRD42024573250Keywords: Adults, Cognitive functions, Cohort studies, Executive functions, Obesity</p>