A new scientific review from UCLA Health has found that factors such as stress, social adversity, and other environmental challenges significantly contribute to the obesity epidemic in the United States. The research, published in Clinical Gastroenterology and Hepatology, emphasizes that beyond diet and exercise, social determinants like income level, education, access to healthcare, neighborhood conditions, discrimination, adverse childhood events, and isolation play a critical role in both the onset and worsening of obesity.
Obesity affects about 40% of American adults and leads to approximately $173 billion in annual healthcare costs. Recent data also shows a tripling of obesity-related cancer deaths in the U.S. between 1999 and 2020.
The review explains how the brain-gut microbiome serves as a connection between environmental influences and obesity risk by generating signaling molecules—such as appetite hormones, inflammatory markers, and neuroactive metabolites—that affect eating habits, cravings for certain foods, metabolism, and exercise routines.
“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 Church, who co-directs the Goodman-Luskin Microbiome Center at UCLA Health. “Reversing the escalating obesity epidemic in America demands a dual approach — personalized, equitable care for individuals and bold, systemic policy reforms that address the root causes.”
“Research shows that social determinants of health — such as access to nutritious food, safe spaces for physical activity, access to resources such as education plumbing, grocery stores, and quality healthcare — are powerful drivers of obesity risk, underscoring the need to address the conditions in which people live, work and grow.”
Lower socioeconomic status often limits health literacy while increasing reliance on cheaper processed foods. In many disadvantaged communities where healthy options are scarce—and where chronic stressors like violence or racism are common—the likelihood of developing obesity rises. Social isolation can also disrupt brain networks responsible for appetite regulation and decision-making.
These influences extend beyond behavior; they lead to biological changes within the brain-gut microbiome system. Consistent exposure to unhealthy foods alters brain structure related to motivation and emotional regulation while reducing gray matter volume. At the same time, poor diets disrupt gut bacteria composition—fueling inflammation that can weaken self-control over eating habits.
Chronic stress—including racism-related stress—alters both brain pathways regulating self-control and gut microbes linked with inflammation. “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 added.
The review notes these changes can start even before birth or during early childhood if exposed to stressful environments or adversity—potentially setting up lifelong susceptibility to obesity.
Church emphasized lasting change requires significant policy action but pointed out steps individuals can take now: prioritizing healthy foods within their means; building supportive relationships; practicing stress-reduction activities like journaling or exercising; fostering empathy; or expressing gratitude—all may help counteract negative influences.
“At the same time,” said Church “healthcare providers have a vital role to play not only by screening for current social determinants of health but also by recognizing how these factors accumulate and evolve over time which is rarely accounted for in today’s clinical practice.”
“By understanding these influences and tailoring treatment plans to account for biological and psychosocial challenges,” Church continued “providers can offer more personalized plans that improve outcomes empowers individuals to take control over their health,and at the same time supports long-term wellness.”
The article is titled “Biopsychosocial and Environmental Factors that Impact Brain-Gut-Microbiome Interactions in Obesity” by Riya Sood et al., published online September 4th 2025.
