New research challenges the idea that obesity harms cognition—suggesting that, in some cases, higher BMI may be linked to stronger memory performance in midlife.
Study: Greater BMI across the lifespan is associated with better midlife cognition: The Bogalusa Heart Study. Image Credit: FGC / Shutterstock
In a recent study published in the journal Scientific Reports, a group of researchers examined the association between body mass index (BMI) across different life stages and cognitive performance in midlife among Black and White Americans.
Background
Can carrying extra weight actually boost your brainpower? With obesity rates projected to affect most adults worldwide by 2030, understanding its impact beyond physical health is critical. While excessive adiposity is widely linked to cardiovascular disease and diabetes, its effects on cognitive function remain less clear.
Some studies warn of cognitive decline, while others reveal unexpected benefits. Cognitive impairment affects millions, reducing independence and straining healthcare systems. As obesity prevalence rises across diverse populations, understanding how weight influences cognitive longevity is crucial.
These uncertainties highlight the need for further investigation, particularly in underrepresented racial groups, to refine public health strategies and interventions.
About the Study
The present study utilized data from the Bogalusa Heart Study, a longitudinal cohort tracking health markers from childhood to adulthood since 1973.
Participants were self-identified Black and White Americans residing in Louisiana. The final analysis included 1,292 individuals (not 1,295) with complete BMI and cognitive data across all epochs. BMI measurements were recorded at multiple visits from early life to midlife. Cognitive assessments were conducted between 2013 and 2016 on participants aged 40-58 years.
BMI was averaged within three developmental periods: childhood/adolescence (4-20 years, represented as percentiles), early adulthood (20-40 years), and midlife (40-58 years).
Cognitive performance was evaluated using standardized tests, including Logical Memory (immediate and delayed recall), Digit Span Forward and Backward, Trail Making Test A and B, and a composite cognitive score.
Linear regression models were used to analyze the association between BMI and cognitive performance, controlling for sex, race, and years of education. Analyses were stratified by sex and race to explore potential differences. The study also applied Holm-Bonferroni corrections for multiple comparisons to enhance statistical rigor. Outliers in BMI and cognitive scores were identified and removed based on interquartile range criteria.
Study Results
The study population comprised 59% women and 34% Black Americans. White Americans generally performed better on cognitive tests compared to Black Americans, though the latter displayed stronger BMI-cognition relationships. The mean years of education were 13.3 ± 2.5, and the average age at cognitive testing was 48.2 ± 5.2 years.
Childhood/adolescence BMI percentiles fell within the healthy range, while early adulthood and midlife BMI averaged in the overweight and class 1 obesity categories. Black Americans exhibited higher early adulthood and midlife BMI than White Americans, and women had higher midlife BMI than men.
Higher BMI in early adulthood and midlife was significantly associated with better cognitive performance in several domains, particularly among men and Black Americans. In men, higher BMI was linked to improved global cognition and memory scores, with stronger effects observed for Logical Memory I, Logical Memory II, and Logical Memory II Recognition. Among Black Americans, higher BMI in early adulthood and midlife was positively associated with Logical Memory I and II scores, indicating a stronger correlation between BMI and cognitive performance within this group despite overall lower test scores compared to White Americans.
The associations varied by sex and race. Despite having higher educational attainment on average, women did not exhibit the same positive correlation between BMI and cognitive function, suggesting potential differences in how body composition and biological factors influence cognition between sexes.
No significant associations were found between BMI changes across epochs and cognitive outcomes, suggesting that cumulative BMI exposure, rather than short-term fluctuations, may be more relevant to cognitive performance.
These findings challenge traditional perspectives on obesity and cognition. While excessive weight is often seen as harmful, in some cases, greater BMI may correlate with better cognitive performance, particularly in memory-related tasks. However, the study does not claim that BMI is directly protective against cognitive decline—further research is needed to clarify the biological mechanisms involved. This has broad implications for healthcare policies, potentially influencing how obesity is managed across different demographics.
By understanding the link between BMI and cognition, public health interventions can be tailored to better address cognitive aging risks in high-risk groups, improving overall brain health.
Conclusions
To summarize, this study provides new insights into the complex relationship between BMI and cognitive function. Higher BMI in early adulthood and midlife was associated with better cognitive performance, particularly in memory-related tasks, among men and Black Americans.
These findings challenge conventional assumptions that obesity is universally detrimental to cognition and highlight the need for further research using more precise measures of adiposity, such as distinguishing subcutaneous versus visceral fat.
Given the disparities in obesity and cognitive decline risks, future studies should explore the underlying biological and social mechanisms driving these associations. Factors such as genetics, physical activity levels, and dietary habits could play a role in shaping the observed relationships. Understanding these dynamics could inform tailored health interventions aimed at preserving cognitive function across diverse populations.
The findings have far-reaching implications, encouraging a shift in how obesity and cognitive health are perceived in public health discussions worldwide.
Journal reference:
- Gwizdala, K.L., Bazzano, L.A., Carmichael, O.T. et al. Greater BMI across the lifespan is associated with better midlife cognition: The Bogalusa Heart Study. Sci Rep (2025), DOI: 10.1038/s41598-025-89363-9, https://www.nature.com/articles/s41598-025-89363-9