CINCINNATI—Everyday stressors may cause long-term metabolic changes and contribute to the development of obesity, say researchers from the University of Cincinnati (UC).
Scientists led by Randall Sakai, PhD, professor in UC’s psychiatry department, and Susan Melhorn, of UC’s neuroscience graduate program, found that stressful experiences can lead to recovery periods marked by overeating and larger, less frequent meals—a pattern that has been linked to weight gain.
The animal study is published in the September 2010 edition of American Journal of Physiology—Regulatory, Integrative and Comparative Physiology.
"Studies have shown that meal patterns can affect metabolism,” says Melhorn. "Fewer, larger meals have been linked to the development of fat, increased triglycerides, lipids and cholesterol. Smaller, more frequent meals have been shown to prevent weight gain.
What wasn’t clear was whether or not stress affected meal patterns.
Sakai and his team used the visible burrow system (VBS), an animal model of chronic social stress, which has been shown to produce stress-associated behavioral, endocrine, physiological and neurochemical changes in animals.
The team placed rats into colonies of four males and two females and monitored them in the VBS. Within a few days, all of the colonies had formed a hierarchy led by one dominant male.
For the next two weeks, researchers monitored food intake relative to a control group and found both dominant and subordinate rates reduced food intake at the beginning of the study. Over time, however, dominant rats resumed normal eating behaviors and subordinate rats continued to eat less.
Following the two-week study, rats were housed individually for three weeks and allowed to eat freely. Both dominant and subordinate rats over-ate compared with the control group, however, dominant rats ate meals more frequently and subordinate rats tended to eat larger meals fewer times each day.
The dominant rats gained weight as lean mass, compared to the control group, while the subordinate rats gained significant fat in the visceral (belly) region. Throughout the recovery period, subordinate rats continued to overeat and gain fat, suggesting long-term, deleterious metabolic changes.
"Our study suggests that stress and subsequent stress recovery puts us at risk for meal patterns that lead to weight gain,” says Sakai.
Sakai says further studies are needed to better understand the relationship between stress and obesity.
The study was funded by a grant from the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health.
Coauthors—all from the University of Cincinnati—include Jeffrey Johnson, Eric Krause, Marie Mooney, Karen Scott and Stephen Woods.