How adolescent obesity is rewiring young brains and shaping mental health

Over 390 million children and adolescents aged 5 to 19 were found overweight in 2022, with 160 million classified as obese. India ranks among the nations with the highest number of overweight adolescents. Behind these numbers lies a greater crisis of how the brains of an entire generation are being reshaped.

Scientific studies show that excess body fat in teenagers can cause chronic inflammation and insulin resistance, says Dr Ranjit Unnikrishnan, Vice Chairman of Dr Mohan’s Diabetes Specialities Centre in Chennai. These conditions can damage the blood-brain barrier and increase oxidative stress, both of which are early contributors to neurodegeneration.

Dr. Sharmila Sankar, a Paediatric Intensivist at Prashanth Hospitals in Chennai, explains that chronic inflammation, driven by immune cells in adipose (fat) tissue releasing pro-inflammatory cytokines, can travel to the brain, contributing to neuroinflammation and even neurodegeneration.

The result? A developing brain is under constant assault, with consequences that ripple through every aspect of a teenager’s life.

Obesity appears to hijack the brain’s architecture in ways that mirror established neuropsychiatric conditions. Shankar said that the brain changes in obese adolescents mirror those seen in conditions like obsessive-compulsive disorder (OCD) and genetic overeating syndromes such as Prader-Willi syndrome.

The implications are profound. Studies link higher body mass index to reduced grey and white matter volume, particularly in the prefrontal cortex- the brain region responsible for self-control and decision-making. These alterations are especially hazardous during adolescence, as the brain is still developing.

Moreover, reduced white matter thickness in obese adolescents resembles structural patterns observed in various neuropsychiatric disorders, including depression, bipolar disorder, and autism spectrum disorder. Thus, excessive weight gain rewires the brain in ways that parallel serious mental health conditions.

These structural changes create a devastating feedback loop that traps adolescents in patterns of dysfunction. These changes affect the brain’s reward system, leading to heightened attentional bias toward food cues and impulsive, reward-driven eating behaviours, explained Sankar. Impaired working memory further weakens appetite control, creating a vicious cycle of overeating and continued weight gain.

The brain, in essence, becomes hijacked by its own inflammation, making the very behaviours that could help- like impulse control and long-term planning, increasingly difficult to access.

The psychological consequences are devastating. Obese adolescents are more vulnerable to depression, anxiety, poor self-esteem, social isolation, and eating disorders like bulimia, binge eating, and anorexia, said Sankar. “Emotional dysregulation, including disrupted sleep-wake cycles and stress-induced eating, further compounds the problem- driving weight gain and reducing quality of life," he added.

For young women, the impact extends to reproductive health, with early weight gain triggering early menarche and increasing risks of polycystic ovarian syndrome and menstrual irregularities.

If not addressed early, unhealthy lifestyle habits in teenagers can lead to future cognitive decline, including neurodegenerative diseases like Alzheimer's and Parkinson’s.

Over time, these changes affect memory, learning and mental clarity thus preventing obesity during adolescence is essential to safeguard long-term brain function.

What can be done?

·      Intake of a diet high in fibre, fruits, vegetables, whole grains and healthy fats supports both physical and cognitive health. Omega-3 fatty acids are found in fish, walnuts and flaxseeds. All these are important for brain development.  

·      Schools can play a vital role in obesity prevention by offering healthy meals in cafeterias, including nutrition education in the curriculum, providing daily physical education classes, and organising health check-ups and weight screening.

·      There must be systemic change that mandates routine health screenings, early counselling by dietitians, policies limiting junk food marketing to children, and investment in youth wellness clinics.

Adolescent obesity isn’t just about weight. It is about protecting the developing brain from a cascade of changes that can last a lifetime. Thus, early intervention is crucial. 

Health