A new study published in JAMA Network Open reveals that women who feel lonely exhibit increased brain activity in areas associated with cravings and the motivation to eat when they view images of high-calorie foods like sugary treats. These findings also correlate with unhealthy eating habits and poor mental health among the same group of women.
Loneliness, or perceived social isolation, is a subjective feeling that involves more than simply being alone. It reflects a dissatisfaction with one’s social connections and has been linked to various health issues, from obesity to heart disease. The COVID-19 pandemic has heightened concerns about the health impacts of loneliness due to increased remote working and reduced physical social interactions.
Although previous studies have connected obesity with psychological conditions like depression and anxiety, the specific brain pathways that link loneliness to eating behaviors remained unclear. In their new study, Arpana Gupta of the UCLA Goodman-Luskin Microbiome Center and her colleagues aimed to explore these connections, focusing on how brain activity in response to food cues varies with feelings of social isolation.
“Researching how the brain processes loneliness and how this is related to obesity and health outcomes hasn’t been done,” said Gupta.
The researchers recruited 93 participants from the Los Angeles area through advertisements, ensuring that all met inclusion criteria, such as being healthy and premenopausal. The study spanned from September 2021 to February 2023.
Participants underwent a series of initial assessments to collect baseline data on various health and demographic factors, including body mass index (BMI), body composition, diet quality, and social and psychological profiles. To assess body composition, the researchers used bioelectrical impedance analysis, a technique that estimates body fat and lean mass by measuring electrical conductivity through tissues. Participants’ diets were evaluated to ascertain their nutritional quality and eating patterns.
A key part of the methodology involved measuring perceived social isolation using the validated Perceived Isolation Scale. This scale assesses both the quantity and quality of the participant’s social interactions and feelings of loneliness. Based on their responses, participants were categorized into groups with high or low perceived isolation.
The brain imaging component of the study was conducted using functional magnetic resonance imaging (fMRI). While in the MRI scanner, participants were shown images of various foods—both high and low calorie—and non-food items. This “food cue task” was designed to elicit neural responses to visual food cues, allowing the researchers to observe which areas of the brain were activated during exposure to different types of stimuli.
The researchers found significant differences in brain activity between women who reported high levels of perceived social isolation (loneliness) and those who reported lower levels. Specifically, when presented with images of high-calorie, sugary foods, the women who felt lonelier exhibited significantly more activity in brain regions associated with cravings and reward, such as the ventral striatum and the insula.
The increased brain reactivity observed in lonely individuals was linked to several adverse outcomes. Firstly, it correlated with higher body fat percentages and lower diet quality among these participants. Lonely individuals also showed greater tendencies towards maladaptive eating behaviors, which include uncontrolled eating and food addiction symptoms. These behaviors are often characterized by a compulsive approach to eating and a dependency on food for emotional relief, similar to mechanisms observed in substance addiction.
In terms of mental health, the findings revealed that loneliness was associated with worse outcomes, including lower psychological resilience and higher levels of anxiety and depression. These mental health challenges could be contributing to, or exacerbated by, the observed eating behaviors.
Lastly, the researchers explored whether these patterns of brain activity and behavior could potentially mediate the relationship between loneliness and health outcomes. They found that brain responses to sweet food cues, in particular, might serve as a pathway through which loneliness influences body composition and mental health. This indicates that the craving for sweet foods in lonely individuals might not just be a symptom of emotional distress but also a contributing factor to broader health issues.
“These findings are interesting because it provides evidence for what we intuitively know,” Gupta said. “When people are alone or lonely, it impacts more than how they are feeling; they underreport what they eat, their desire to eat, and their cravings especially for unhealthy foods.”
“If you have more cravings, you eat more and may have more anxiety or depression, which may lead you to eat more,” added Xiaobei Zhang, a postdoctoral researcher and the study’s lead author, likening this pathway to a “vicious cycle between unhealthy eating and negative mental symptoms.”
Despite its insights, the study has limitations. Its cross-sectional design means it can only show associations, not causality, and its findings are based on a relatively small and homogeneous sample—all participants were female and from a specific geographic area.
Future research could expand on these findings with a more diverse and larger sample size and longitudinal studies to explore how changes in loneliness and social relationships over time might impact eating behaviors and brain activity. Further studies could also integrate biological measures, such as hormonal levels or genetic markers, to understand better the mechanisms underlying the observed relationships.
The study, “Social Isolation, Brain Food Cue Processing, Eating Behaviors, and Mental Health Symptoms,” was authored by Xiaobei Zhang, Soumya Ravichandran, Gilbert C. Gee, Tien S. Dong, Hiram Beltrán-Sánchez, May C. Wang, Lisa A. Kilpatrick, Jennifer S. Labus, Allison Vaughan, and Arpana Gupta.