Adolescent obesity linked to structural brain changes affecting memory and emotion

Key Takeaways:

• Adolescents living with abdominal obesity exhibit enlarged brain structures associated with memory, learning, and emotional regulation, particularly the hippocampus and amygdala.
• These neurological changes are compounded by social inequalities, with adolescents in lower-opportunity environments experiencing even more pronounced alterations in brain development.
• The findings underscore the potential long-term cognitive and emotional consequences of adolescent obesity and highlight the importance of early intervention to promote both physical and brain health.

New Research Shows Obesity in Teenagers Alters Brain Development

New findings presented at the European Congress on Obesity (ECO 2025) reveal that adolescents living with obesity—particularly abdominal obesity—exhibit significant alterations in brain structure, with enlarged regions responsible for learning, memory, and emotional regulation.

The research, led by Dr Augusto César F. De Moraes of the UTHealth Houston School of Public Health in Austin, Texas, involved an analysis of thousands of teenagers in the United States. According to Dr De Moraes, “This is particularly alarming, given that the teenage years are such an important time for brain development.” The results raise concerns about the broader neurocognitive implications of adolescent obesity, extending beyond physical health.

A Global Rise in Adolescent Obesity

The prevalence of obesity among children and adolescents has increased dramatically across the globe. Between 1990 and 2022, the proportion of girls living with obesity rose from 1.7% to 6.9%, and among boys, from 2.1% to 9.3%.

In the United States, more than one in three children aged 5 to 14 are now living with overweight or obesity—36.2% of boys and 37.2% of girls—representing over 15 million children. These trends pose an escalating public health challenge, with growing attention now being paid to the cognitive and neurological consequences.

Studying Brain Structure in Adolescents

To explore how obesity and social determinants affect brain development, Dr De Moraes and collaborators from the United States, Brazil, and Spain analysed data from 3,320 children participating in the Adolescent Brain Cognitive Development (ABCD) study. This longitudinal research project investigates how early life experiences influence brain and behavioural development.

Participants, recruited from 21 cities across 17 U.S. states, were followed over four years—initially between 2016 and 2018, and again from 2020 to 2022. At the start of the study, the average age was 9.9 years, with girls comprising 47.4% of the cohort. Obesity status was determined using body mass index and waist circumference, with approximately 34.6% of participants identified as having abdominal obesity at baseline.

Brain Regions Affected by Obesity

Structural MRI scans assessed the volume of key subcortical brain regions, including:

• Hippocampus – involved in memory and learning
• Amygdala – responsible for emotional regulation
• Caudate – plays a role in movement control
• Accumbens, pallidum, putamen, thalamus – other subcortical structures involved in sensory and motor processing

The analysis found that several of these regions were significantly larger in adolescents with abdominal obesity compared to their peers without. The hippocampus was approximately 6.6% larger, and the amygdala 4.3% larger in adolescents with abdominal obesity. Notably, the amygdala was particularly enlarged in those with the highest levels of abdominal fat (waist-to-height ratio > 0.5), prompting concerns about how excess fat might influence emotional processing.

Other brain regions, such as the thalamus and caudate, also exhibited slight increases in size, although these were less pronounced.

The Influence of Social Inequality

To evaluate how environmental factors may further affect brain development, researchers used the Child Opportunity Index, a tool that assesses the quality of a child’s surroundings—including access to education, green space, nutritious food, and neighbourhood safety.

The findings revealed that adolescents from lower-opportunity areas had reduced development in critical brain structures such as the hippocampus, amygdala, and putamen, compared with their peers from higher-opportunity areas. Dr De Moraes stated, “This difference was even more pronounced among adolescents with persistent abdominal obesity.”

These results highlight the compounding impact of both health and social disparities on adolescent neurodevelopment.

Interpreting the Neurological Changes

The researchers caution that both underdevelopment and excessive enlargement of brain structures can be harmful in the context of a developing brain. While reduced brain growth—as seen in adolescents from disadvantaged backgrounds—may reflect stunted neurodevelopment, excessive brain volume—potentially caused by inflammation from obesity—may also interfere with optimal functioning.

Long-Term Implications and the Need for Early Intervention

Dr De Moraes expressed concern about the long-term consequences of these changes, stating:

“Our findings suggest that obesity, particularly abdominal obesity, can impair teenagers’ learning, memory, and emotional control. I worry about how these changes, which are occurring at the age of 13 or 14, might affect them later in life.

There’s even a chance they could be at a higher risk of things like memory problems or dementia as they get older.”

He continued:

“That’s why we believe supporting healthier habits early on is so important, not just for physical health, but for brain health too.

Treating and preventing adolescent obesity won’t only improve health – it may improve brain health, too.”

Conclusion

This large-scale study adds to growing evidence that adolescent obesity, particularly when concentrated in the abdominal region, can have significant effects on brain structure, potentially influencing cognitive and emotional development. These findings emphasise the importance of addressing both obesity and social inequalities early in life to foster not only physical wellbeing but also healthy brain development.

CCH Insight:

The results of this study are concerning. We already know that obesity in childhood can increase the risk of cardiometabolic diseases, but this research suggests the impact could be more wide-ranging and obesity could impair teenagers’ learning, memory, and emotional control. It adds weight to the case for early identification and intervention for children with obesity.