Understanding Why Obesity Is Considered a Disease: A Simple Guide

Did you know obesity is no longer just called "obesity"? It’s now recognized as ABCD — Adiposity-Based Chronic Disease. This shift reflects a deeper understanding: obesity isn’t simply about calories in vs. calories out — there’s much more beneath the surface.Curious? Read on to uncover the full story.

How Does Our Brain Control Weight?

Our brain plays a central role in regulating body weight through complex signaling pathways that affect appetite, energy expenditure, and fat storage. Two critical pathways in the brain work like opposing forces:

The Anorexigenic Pathway – The "Stop Eating" Signal

This pathway, involving neurons that produce a protein called proopiomelanocortin (POMC), signals the body to eat less and burn or store less fat. When this pathway is active, you feel satisfied and your body reduces fat storage.

 

The Orexigenic Pathway – The "Eat More" Signal

This pathway includes neurons producing Agouti-related protein (AgRP), which stimulate hunger and encourage the body to eat more and store fat for energy reserves. In many people with obesity, this pathway can be overly active, leading to increased food intake and fat storage even when calorie intake is controlled.

Together, these pathways balance our body's energy needs. When the orexigenic pathway dominates, it's much harder to lose weight, regardless of lifestyle efforts. This biological tug-of-war explains why some individuals can gain weight easily and struggle to lose it despite healthy habits.

The Brain’s Role Beyond Appetite

Beyond these appetite pathways, obesity affects and is affected by changes in brain structure and function. Studies show that obesity can lead to inflammation in the hypothalamus (a key brain region involved in energy balance), which disrupts normal signaling and promotes further weight gain. Additionally, obesity is associated with reductions in brain gray matter and cortical thickness, particularly in areas related to decision-making, reward, and impulse control, which may perpetuate overeating behaviors.

Chronic obesity may also influence cognitive functions such as memory and executive function and contributes to increased risk of neurodegenerative diseases through inflammatory and metabolic pathways.

Why Is Recognizing Obesity as a Disease Important?

Understanding obesity as a disease rooted in brain biology changes the stigma around it. Instead of blaming individuals for a perceived lack of discipline, it highlights the need for treatments that address neurological pathways, such as medications targeting brain appetite centers, alongside lifestyle interventions.

This perspective:

• Encourages compassion and support for those living with obesity.
• Promotes medical approaches including therapies that modulate brain signals controlling hunger and fat storage.
• Helps guide research into new treatments that target the underlying disease mechanisms rather than symptoms alone.

Moving Forward with Knowledge and Empathy

Recognizing the brain’s pivotal role in obesity empowers both patients and healthcare providers. It stresses that overcoming obesity is not just about "willpower" but managing a disease with deep biological roots. With ongoing research, better treatments and strategies are emerging, offering hope for effective and sustained weight management.

Dr Manohar K N

Lead Consultant Physician & Diabetologist SPARSH Hospital
MD, DNB, MNAMS,  
Triple FRCP (Edinburgh, Glasgow & London), 
FEAC - Fellow of Euro-Asian Academy of Cardiology 
Fellow of RSSDI, Fellow Diabetes India
www.drmanoharkn.com/

References :

1. Schwartz, M.W., et al. The Neuropathology of Obesity: Insights from Human Disease. PMC, 2013. https://pmc.ncbi.nlm.nih.gov/articles/PMC3880612/
2. American Medical Association. For Patients with Obesity, Brain's Pathways Tell the Tale. AMA, 2025. https://www.ama-assn.org/delivering-care/chronic-diseases/patients-obesity-brain-s-pathways-tell-tale
3. Janowitz, D., et al. Structural Brain Changes Associated with Overweight and Obesity. PMC, 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC8302366/
4. University of Wisconsin–Madison. Research Team Discovers Brain Pathway Responsible for Obesity. 2008. https://news.wisc.edu/research-team-discovers-brain-pathway-responsible-for-obesity/
5. Morys, F., et al. Neural correlates of obesity across the lifespan. Commun Biol, 2024. https://pubmed.ncbi.nlm.nih.gov/38806652/
6. Medawar, E., Witte, A.V. Impact of obesity and diet on brain structure and function: a gut-brain-body crosstalk. Proc Nutr Soc, 2022. https://pubmed.ncbi.nlm.nih.gov/36345149/