a kind of disease. What's unclear is how being being lonely leads to these adverse effects on our health. A new study looks at one possibility – that loneliness makes people feel hungrier than normal, thus increasing their food intake and putting them at risk of obesity with all its associated health problems.
Lisa Jaremka and her colleagues asked 42 women (average age 53) to fast for 12 hours before visiting the psych lab. On arrival in the morning, the women were asked to eat an entire 930 calorie meal consisting of eggs, turkey sausage, biscuits and gravy. Before they ate the meal and several times during the seven hours afterwards the women rated their hunger. Their feelings of extreme loneliness had been recorded five months earlier as part of a different study. Their ghrelin levels (ghrelin is a hormone that's associated with hunger and promotes eating) were recorded by blood test before the meal and 2 and 7 hours later.
Among only the women with a healthy weight (based on their BMI), those who reported feeling more lonely exhibited higher ghrelin levels at the end of the day they visited the lab, and said they felt hungrier. This result is consistent with another recent study by the same researchers, that found women who'd experienced more interpersonal stress had higher ghrelin levels and lower leptin (an appetite-suppressing hormone).
Why should loneliness be associated with feeling more hungry? Jaremka and her team speculate that it could be an evolutionary hangover and adaptive in the sense that hunger encourages eating, which encourages greater social bonding. "Eating was a highly social activity throughout human evolution, and today meals are often eaten with other people," they explain. Other research has shown that eating comfort food prompts thoughts of relationships. "Consequently," the researchers said, "people may feel hungrier when they feel socially disconnected because they have either implicitly or explicitly learned that eating helps them feel socially connected and/or provides them with an opportunity for social connection." It's unclear why the same process wasn't triggered in the overweight women.
The study has some methodological issues, among them: the lack of a current loneliness measure; no male participants; and half the small sample of women were cancer survivors recruited from an earlier study. This may limit the generalisability of the findings, but note the main results from this study were the same for all participants regardless of their medical history.
Jaremka, L., Fagundes, C., Peng, J., Belury, M., Andridge, R., Malarkey, W., & Kiecolt-Glaser, J. (2015). Loneliness predicts postprandial ghrelin and hunger in women Hormones and Behavior, 70, 57-63 DOI: 10.1016/j.yhbeh.2015.01.011
Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.