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In A Nutshell

Married people who feel emotionally supported by their spouse had BMIs about five points lower than married people lacking that support, a pattern not seen among unmarried individuals

Supportive marriages were associated with higher activity in a brain region responsible for impulse control when participants viewed images of food

Gut bacteria in well-supported individuals produced more anti-inflammatory compounds and fewer harmful metabolites linked to cognitive problems

Oxytocin, the hormone released during bonding and physical affection, may connect relationship quality to both brain function and gut chemistry, though more research is needed to confirm this pathway

Married people who feel emotionally supported by their partners tend to weigh less than those in marriages lacking that connection, according to research from UCLA. The difference isn’t trivial, either. Married individuals who reported high emotional support had body mass indexes averaging about five points lower than their less-supported counterparts.

The study, published in Gut Microbes, offers a biological explanation for why strong relationships might protect against weight gain. Researchers found that supportive marriages appear to boost levels of oxytocin, the hormone linked to bonding and trust, which in turn affects how the brain responds to food and how the gut processes nutrients.

Why Marriage Alone Doesn’t Tell the Whole Story

Previous research on marriage and body weight has produced conflicting results. Some studies show married people gain weight after tying the knot, while others find they’re healthier than their single peers. This new research helps explain the mixed findings by focusing not on marriage alone, but on the quality of emotional connection within it.

Researchers recruited 94 adults from the Los Angeles area and gathered an unusual combination of data: brain scans showing how participants responded to images of food, stool samples to analyze gut bacteria and metabolites, blood tests measuring oxytocin levels, and questionnaires about their relationships and eating habits.

Participants answered questions about emotional support, specifically whether they felt they received comfort and understanding from others. They also reported their marital status and completed assessments measuring food addiction symptoms and perceived stress.

When the researchers compared married individuals who felt highly supported to those who felt less supported, the BMI gap was substantial. Among unmarried participants, however, emotional support levels showed no such relationship with weight.

Finding the one does more for your heart than might realize. (Photo by Giorgio Trovato on Unsplash) Oxytocin Links Bonding to Appetite

Oxytocin has long been known as the “bonding hormone,” released during physical touch, childbirth, and moments of emotional connection. More recent research has revealed it also plays a role in appetite regulation and eating behavior.

In this study, married individuals tended to show higher oxytocin levels than unmarried participants, though this trend did not reach conventional statistical significance. The researchers propose that stable, committed relationships may stimulate ongoing oxytocin release, which then influences both brain function and gut chemistry in ways that affect eating.

Brain scans revealed another piece of the puzzle. When viewing images of food, married people with high emotional support showed greater activity in the dorsolateral prefrontal cortex, a region responsible for executive control and impulse regulation. This area helps people resist cravings and make thoughtful decisions rather than acting on immediate urges.

Among unmarried participants, emotional support levels didn’t produce the same difference in brain activity. The researchers suggest that the particular dynamics of marriage may create a kind of “training ground” for self-control, requiring partners to regularly override selfish impulses in favor of relationship-oriented goals.

Gut Bacteria Respond to Relationship Quality

The study also examined tryptophan, an amino acid obtained from food that the body uses to make serotonin and other compounds. Gut bacteria help process tryptophan into various metabolites, some beneficial and others potentially harmful.

Participants who reported higher emotional support showed elevated levels of indole and indole-3-carboxylate, compounds with anti-inflammatory and neuroprotective properties. They also had lower levels of 3-indoxyl sulfate, a substance associated with inflammation and cognitive problems.

Married individuals with high emotional support showed increased picolinate, a tryptophan metabolite with immune-regulating effects. Low picolinate levels have been linked to depression and neurodegenerative diseases in prior research, though this study did not examine those conditions.

These gut changes respond to both the quality of relationships, measured by emotional support, and the structure of relationships, indicated by marital status. The pattern points toward a mechanism where social environments shape the bacterial ecosystem of the digestive tract, which then influences brain function and metabolic health.

A Coordinated System

Using statistical modeling, the researchers tested whether these various findings fit together into a coherent pathway. Their analysis supported a model where positive social relationships increase oxytocin levels, which then influence both the brain regions involved in eating regulation and the gut metabolites involved in inflammation and energy balance.

The connection between brain activity and gut metabolites was particularly strong, indicating coordinated activity across the central nervous system and digestive tract. Oxytocin may facilitate this communication, helping the brain regulate eating behavior while simultaneously affecting peripheral metabolic processes.

Food addiction symptoms also differed based on emotional support. Participants who felt highly supported reported fewer of these behaviors regardless of marital status. Poor social support has previously been identified as a risk factor for eating disorders, and this research adds evidence that quality connections may protect against problematic eating patterns.

The sample was predominantly Hispanic, with participants ranging from 18 to 54 years old. Most had BMIs in the overweight or obese range, limiting how broadly the findings might apply. The study’s cross-sectional design means it captured a snapshot in time rather than tracking changes over months or years.

Married participants tended to be older than unmarried ones, and while the researchers controlled for age statistically, differences between the groups could still influence the results. The method used to measure oxytocin may have captured related peptides along with the hormone itself, potentially affecting precision.

Obesity affects more than 40 percent of American adults and contributes to heart disease, diabetes, and other chronic conditions. Interventions typically focus on diet and exercise, but this research indicates relationship quality might deserve attention too. Feeling understood and supported by a partner affects more than mood. It may shape brain function, alter gut chemistry, and influence the body’s regulation of appetite and weight.

Paper Summary Limitations

The study’s cross-sectional design prevents establishing cause-and-effect relationships. Longitudinal research would be needed to determine whether changes in relationship quality lead to changes in weight, oxytocin, or gut metabolites over time. The sample size of 94 participants limited the ability to detect differences between subgroups, particularly regarding sex. Most participants had BMIs in the overweight or obese range, which may limit how well findings apply to people across the full weight spectrum. Married participants were older than unmarried ones on average, introducing potential confounding despite statistical adjustments. The oxytocin measurement method did not use sample extraction, meaning the values may include immunoreactive peptides besides free oxytocin. The emotional support scale used only two questions, and dichotomizing scores into high and low categories may have reduced sensitivity to individual differences. The focus on tryptophan metabolites, while hypothesis-driven, means other potentially relevant gut compounds were not examined.

Funding and Disclosures

The research was supported by grants from the National Institutes of Health (R01 MD015904, K23 DK106528, and R03 DK121025), all awarded to senior author Arpana Church. The funders had no role in study design, data collection, analysis, interpretation, or publication decisions. Arpana Church disclosed serving as a scientific advisor to Yamaha. All other authors reported no conflicts of interest. The study received approval from UCLA’s Institutional Review Board, and all participants provided written informed consent.

Publication Details

Title: Social bonds and health: exploring the impact of social relations on oxytocin and brain–gut communication in shaping obesity

Authors: Xiaobei Zhang, Tien S. Dong, Gilbert C. Gee, Lisa A. Kilpatrick, Hiram Beltran-Sanchez, May C. Wang, Allison Vaughan, and Arpana Church

Affiliations: G. Oppenheimer Center for Neurobiology of Stress & Resilience, Vatche and Tamar Manoukian Division of Digestive Diseases, David Geffen School of Medicine, Goodman-Luskin Microbiome Center, Department of Community Health Sciences at the Fielding School of Public Health, and California Center for Population Research, all at the University of California, Los Angeles

Journal: Gut Microbes, Volume 17, Issue 1, Article 2566978 | Published: December 3, 2025 | DOI: 10.1080/19490976.2025.2566978 | Data Availability: Deidentified brain data available through the pain repository portal (https://www.painrepository.org/). Raw microbiome sequences accessible at NIH NCBI BioProject (ID: PRJNA946906).