When scientists study obesity and weight-loss treatment, it's most often about genetics, lack of physical activity and poor eating habits. However, new findings show that stress, hardship, isolation and social inequality create the biological environment that underpins the condition that now affects around 40% of US adults.
Researchers from UCLA Health have conducted a comprehensive review that demonstrates how social challenges reshape the gut's bacteria and brain circuitry in ways that make it easier to gain weight and much harder to keep it off. They found that these environmental and social factors – including income, education, healthcare access, neighborhoods, discrimination, childhood trauma, isolation and loneliness – exacerbate inflammation, stimulate appetite signals and change brain chemistry, essentially rewiring the body to consume more calories.
“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," said lead researcher Dr Arpana Church, co-director of the Goodman-Luskin Microbiome Center at UCLA Health.
At the heart of this complex relationship is the brain–gut–microbiome axis – an intimate communication network linking our social environment to our biological responses. Through signaling molecules – like appetite-stimulating hormones, inflammatory markers, and neuroactive metabolites – environmental stresses reshape not only what and how we eat, but also our metabolism and cravings, and our physical activity.
Many of the factors that increase the risk of obesity are well known. Socioeconomic hardship often forces reliance on cheap, calorie-dense processed foods, which can change brain circuits linked to reward, motivation and emotional regulation. These foods have also been found to reduce gray matter volume, impairing self-control.
Poor diets and chronic stress foster gut bacteria imbalances and inflammation that is rooted in the microbiome. These changes further erode motivation and self-regulation, promoting emotional eating and dependence on ultra-processed foods. In addition to this, the researchers found evidence that chronic stress – from racism, violence or social isolation – also reshapes brain pathways and the microbiome to promote inflammation and weaken self-control, raising obesity risk even without dietary changes.
And it doesn't just start in adulthood. Stress and adversity during pregnancy and childhood can disrupt the gut–brain communication network early in life, possibly even in the womb, setting the stage for lifelong obesity struggles.
“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. "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."
While the researchers emphasize that lasting change on a societal level needs to come through sweeping policy reform, they note that immediate steps can be taken by individuals and healthcare providers to make a difference on a more personal level.
Of course, budget-friendly nutritious food, safe areas to exercise, affordable healthcare and good education, as well as adequate plumbing and accessible grocery stores – particularly in disadvantaged neighborhoods – are pivotal. But, individually, the researchers suggest small changes could serve as effective interventions. These include opting for affordable nutritious foods when possible, fostering stronger social connections and engaging in stress-relieving habits like journaling or spending time in nature.
“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 team also believes that clinicians should look at screening patients for detrimental environmental factors – isolation, food insecurity, stress history – to develop treatment plans that better address the psychosocial and biological links in obesity.
"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," said Church. “By understanding these influences and tailoring treatment plans to account for biological and psychosocial challenges, 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."
In May, a Yale School of Medicine study found that less than 3% of people eligible for life-changing GLP-1 medications are able to afford them, with government insurance not covering access to the drugs.
“The cost and the insurance coverage is the primary reason for people not getting this drug,” said Yuan Lu, co-author of the Yale study. “There is another part of the story. Even if the doctor prescribes it, you can imagine, because of the insurance, because of the cost issue, people come to the pharmacy, they find out it’s too high out-of-pocket cost, and they don’t fill the prescription.”
Obesity costs the US healthcare system around US$173 billion. Across the globe in 2021, according to the World Health Organization, 3.7 million people died as a result of obesity-related noncommunicable diseases (NCDs) including cardiovascular diseases, diabetes, cancers, neurological disorders, chronic respiratory diseases and digestive disorders.
The research was published in the journal Clinical Gastroenterology and Hepatology.
Source: UCLA Health
