In a study of mice, Georgetown University Medical Center researchers found that social isolation and fatty foods elevated levels of a neurotransmitter in the brain associated with insulin resistance and breast cancer.
Moreover, rodents that were denied socialization but fed a normal diet had high levels of neuropeptide Y and also formed more structures in the mammary gland that were prone to becoming cancerous.
"We have yet to translate these findings to humans, but it does suggest that social isolation is a potent stressor and initiates a robust central nervous system response," said lead author Allison Sumis.
In a controlled study, the team found that 92 percent of mice who were isolated and ate a high-fat diet developed tumors, and 67 percent of the animals who lived in groups but had poor diets experienced abnormal growths. Of the rodents that ate normal diets, 36 percent ended up with tumors — whether they were isolated or not.
Authors of the study noted that it is possible that stress relating to loneliness exacerbated the negative effects of a fatty diet.