Summary: A large new study finds that adolescents with abdominal obesity show larger volumes in brain regions linked to memory and emotional regulation, raising concerns about how excess body fat may influence brain development. MRI scans of over 3,300 young people revealed enlarged hippocampus and amygdala in those with abdominal obesity—especially among teens with higher waist-to-height ratios—while youth living in lower-opportunity neighborhoods showed reduced development in several key areas.
Researchers caution that both abnormal overgrowth and underdevelopment in these regions can interfere with cognitive and emotional functioning, potentially increasing long-term risk for mental health problems and cognitive decline. The results were presented at the European Congress on Obesity (ECO 2025) and were led by Dr. Augusto César F. De Moraes of UTHealth Houston School of Public Health in Austin.
- Brain growth changes: Adolescents with abdominal obesity had an approximately 6.6% larger hippocampus and a 4.3% larger amygdala compared with peers without abdominal obesity.
- Emotional regulation: Enlargement of the amygdala was most pronounced in teenagers with very high abdominal fat (waist-to-height ratio over 0.5), suggesting potential effects on how the brain processes emotions.
- Social inequality: Teens from lower-opportunity neighborhoods showed reduced development in the hippocampus, putamen and amygdala, and these disparities were greater among those with persistent abdominal obesity.
Global rates of childhood and adolescent obesity have risen sharply: between 1990 and 2022 the proportion of girls living with obesity increased from 1.7% to 6.9%, while among boys it rose from 2.1% to 9.3%. In the United States, more than one in three children aged 5 to 14 are estimated to be living with overweight or obesity—roughly 36.2% of boys and 37.2% of girls—amounting to over 15 million children.
Previous research has linked obesity, and particularly abdominal obesity, to alterations in brain development. The current study adds new evidence by examining structural MRI data across multiple subcortical regions, and by considering neighborhood-level opportunity measures alongside body composition.
The analysis used data from 3,320 participants enrolled in the ABCD study, a long-term research project that follows how childhood experiences affect brain development and health. Participants were recruited from cities across 17 U.S. states and followed for four years between 2016–2018 and 2020–2022. At baseline the average age was 9.9 years and 47.4% of participants were girls. About 34.6% were classified as having abdominal obesity based on waist circumference measurements.
Researchers measured volumes of subcortical structures including the hippocampus (critical for learning and memory), amygdala (central to emotion regulation), caudate and putamen (involved in movement and behavioral control), pallidum, nucleus accumbens and thalamus (a sensory relay). They also assessed neighborhood-level disparities using the Child Opportunity Index, which captures local access to quality education, healthy foods, safe streets, green space and other features that support child development.
Key findings show larger hippocampal and amygdala volumes in adolescents with abdominal obesity. The hippocampus was about 6.6% larger and the amygdala about 4.3% larger in those with abdominal obesity compared with peers without. The amygdala increase was most evident in adolescents whose waist-to-height ratio exceeded 0.5—an indicator of significant abdominal adiposity. Smaller increases were detected in the thalamus and caudate.
At the same time, teenagers living in lower-opportunity neighborhoods exhibited reduced development in the hippocampus, putamen and amygdala relative to teens in higher-opportunity areas. These reductions were amplified among adolescents with persistent abdominal obesity, reinforcing the combined impact of social determinants and excess adiposity on brain development.
The study authors emphasize that deviations in brain growth in either direction—reduced growth linked to social disadvantage or enlarged volumes possibly related to inflammation from obesity—can be harmful during adolescence, a critical window for neural maturation. Dr. De Moraes warns that such changes in early teenage years could have lasting consequences for learning, memory and emotional control and might increase risks for cognitive problems later in life.
“Our findings underscore the importance of preventing and treating adolescent obesity not only to protect physical health but also to support healthy brain development,” Dr. De Moraes said. He and colleagues call for policies and interventions that address both health behaviors and structural inequalities to promote better outcomes for young people.
About this obesity, neurodevelopment, and memory research news
Author: Augusto César F. De Moraes
Source: European Society for the Study of Obesity
Contact: Augusto César F. De Moraes – European Society for the Study of Obesity
Image: The image is credited to Neuroscience News
Original research presentation: Findings presented at the European Congress on Obesity (ECO 2025)