Supportive marriage linked to lower obesity risk through novel brain-gut pathway

A new study published in the journal Gut Microbes provides evidence that supportive social relationships may influence physical health through specific biological pathways involving the brain and the gut. The findings suggest that high-quality marital bonds are associated with lower body mass index and healthier eating behaviors, potentially regulated by the hormone oxytocin and its interaction with the microbiome.

Social isolation is often recognized as a significant risk factor for various health issues, with some data suggesting its impact on mortality is comparable to smoking or physical inactivity. While statistical associations between relationships and health outcomes are well-documented, the biological mechanisms driving these effects remain less clear. Science has not fully explained how intangible social dynamics translate into tangible physical changes like weight regulation or metabolic health.

Previous work indicates that the hormone oxytocin plays a role in social bonding and appetite regulation. Simultaneously, the communication system between the brain and the gut microbiome is known to influence obesity. The authors of the current study aimed to bridge these distinct areas of research. They sought to determine if social relationships physically alter the body through an integrated pathway connecting oxytocin, brain activity related to food cravings, and gut metabolites.

The research team recruited 94 participants from the Los Angeles community. The group included adults of various ages and racial backgrounds, though most participants had a body mass index classifying them as overweight or having obesity. The researchers collected a wide array of data to capture both psychological and biological profiles.

Participants provided information about their marital status and completed the Brief Coping Orientation to Problems Experienced scale. This assessment measured their perceived levels of emotional support. The team categorized emotional support based on whether participants felt they received comfort and understanding from others.

To measure biological responses, the team utilized functional magnetic resonance imaging. This allowed them to observe brain activity while participants viewed images of food compared to non-food control images. The researchers also collected fecal samples to analyze the gut microbiome and specific metabolites derived from tryptophan. Additionally, plasma oxytocin levels were measured from blood samples in a subset of 77 participants.

The analysis revealed complex interactions between marital status and emotional support. Being married was not automatically associated with better health outcomes on its own. Instead, married individuals who also reported high levels of emotional support exhibited significantly lower body mass index compared to married individuals reporting low support. This difference in body mass index based on emotional support levels was not observed among unmarried participants.

The brain imaging data offered insights into how these social factors might influence eating behaviors. Married participants with high emotional support showed greater activity in the dorsolateral prefrontal cortex when viewing food cues. This region of the brain is typically associated with executive control, planning, and the inhibition of cravings.

The findings indicate that supportive partnerships may bolster the neural circuits required to resist unhealthy food impulses. Lead author Dr. Arpana Church noted that maintaining a long-term partnership requires overriding impulses and aligning with long-term goals. This process may strengthen the same brain circuits involved in managing eating behavior.

Analysis of the fecal samples showed that social factors were associated with levels of tryptophan metabolites. Tryptophan is an amino acid that the body processes into various compounds. Some of these compounds support health, while others can be harmful.

Perceived emotional support was linked to higher levels of compounds like indole and indole-3-carboxylate. These metabolites are generally considered beneficial for their roles in reducing inflammation and protecting nerve function. Conversely, lower support was linked to higher levels of 3-indoxyl sulfate, a compound often associated with negative health outcomes and inflammation.

The study also found a marginal association where married individuals tended to have higher levels of plasma oxytocin. Oxytocin is a peptide hormone often implicated in social bonding and stress regulation. It has also been shown to reduce food intake and dampen activation in brain regions associated with food motivation.

Using a statistical method called structural equation modeling, the researchers proposed a unified pathway. The model suggests that positive social relations may upregulate oxytocin. This upregulation appears to coordinate with enhanced brain regulation of cravings and a healthier metabolic profile in the gut.

Collectively, these biological alterations contribute to reduced obesity risk. The model indicates a system where the brain and the gut communicate to regulate health, with social bonds acting as a primary influence. This supports the idea that obesity is not solely a result of diet and metabolism but is also shaped by social and neurobiological factors.

The results challenge oversimplified views about marriage and weight. They highlight that the quality of the relationship is a determining factor. The protective benefits regarding metabolism and self-control were most pronounced among married participants who endorsed greater emotional support.

There are some limitations. The study used a cross-sectional design, meaning it captured data at a single point in time rather than following participants over years. This design prevents definitive conclusions regarding cause and effect, as it is possible that health status influences social relationships.

The researchers suggest that future work should aim to replicate these findings in larger, more diverse groups. Longitudinal studies would be necessary to track how changes in relationship quality influence biological markers over time. Investigating other metabolite pathways beyond tryptophan could also provide a more comprehensive picture.

These findings open potential avenues for obesity prevention and treatment. They imply that interventions focusing on diet and exercise alone may be incomplete. Incorporating strategies to build strong, positive social relationships could be a necessary component of holistic health care.

Therapies that target the oxytocin system or the gut microbiome might also prove useful for individuals lacking strong social support. For example, probiotics or dietary changes that influence tryptophan metabolism could potentially mimic some of the protective benefits observed in the study.

Ultimately, the research emphasizes that humans are inherently social beings. The study provides biological evidence that social connections are not just emotionally fulfilling but are deeply embedded in physical physiology. Positive bonds appear to act as a buffer against obesity by reinforcing the body’s natural regulatory systems in the brain and the gut.

The study, “Social bonds and health: exploring the impact of social relations on oxytocin and brain–gut communication in shaping obesity,” was authored by Xiaobei Zhang, Tien S. Dong, Gilbert C. Gee, Lisa A. Kilpatrick, Hiram Beltran-Sanchez, May C. Wang, Allison Vaughan, and Arpana Church.