Obesity affects about 40% of American adults, yet diet and exercise alone don’t explain why so many people struggle with weight.
A new review from UCLA Health, published in Clinical Gastroenterology and Hepatology, highlights how stress, social adversity and environmental challenges interact with the gut and brain to drive obesity risk.
The paper describes how social determinants of health, including income, education, neighborhood disadvantage, food access, discrimination and isolation, reshape gut bacteria and brain networks in ways that alter appetite, metabolism and self-control. These factors can create a cycle of cravings, emotional eating and weight gain that’s hard to break.
“Our findings reveal that tackling obesity requires more than focusing on individual choices — it demands recognizing the powerful role that social and environmental forces play in shaping gut health, behavior and long-term health outcomes,” said lead author Dr. Arpana Church, co-director of the Goodman-Luskin Microbiome Center at UCLA Health.
Research shows that chronic stress and poor diets can physically change the brain, reducing gray matter volume and disrupting networks that regulate motivation, reward and decision-making. At the same time, unhealthy eating patterns alter gut microbes, fueling inflammation that further undermines self-control. Even before birth, early-life adversity can prime the brain-gut system for obesity risk later in life.
Neighborhoods also matter. Limited access to healthy food and safe spaces for exercise, combined with higher exposure to stress and violence, increase the risk of obesity.
“Neighborhood disadvantage is also linked to reduced gut microbiome diversity and a higher presence of harmful bacteria — factors that further impair metabolism and heighten the risk of obesity and related diseases,” Church noted.
The authors stress that lasting solutions will require both bold policy changes, to improve food access, housing, education and health care, and personalized care tailored to patients’ lived experiences. While systemic reforms are essential, individuals can still take steps such as prioritizing nutritious foods within their budget, building social connections and practicing stress-reducing activities like exercise, journaling and time in nature.
“By understanding these influences and tailoring treatment plans to account for biological and psychosocial challenges, providers can offer more personalized plans that improve outcomes and empower individuals to take control over their health,” Church said.
This research was supported by grants from the National Institutes of Health. Dr. Church disclosed consulting for Yamaha; all other authors reported no conflicts of interest.